Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Although open repair is traditionally pursued for proximal aorta pathology, endovascular stent grafting is possible in certain cases of type A dissection and proximal thoracic aortic aneurysm. A 2011 study demonstrated a 98% technical success rate for TEVAR in the treatment of 45 patients with type A dissection in which the entry tear was at least 2.5 cm from the coronary ostia [52]. Notably, transposition of the supra-aortic vessels was necessary in nearly half of the patients in this study to ensure an adequate landing zone. Other authors recommend a minimum distance of 1 cm from the intimal tear entry site to the sinotubular junction and brachiocephalic trunk [11]. CTA is essential in planning for these cases to avert compromise of coronary and brachiocephalic circulation as well as aortic valve dysfunction. An essential aspect of pre-TEVAR planning is evaluation of the iliofemoral vasculature. Thoracic aorta endografts tend to be larger than their abdominal counterparts, requiring insertion sheaths with outer diameters up to 27 French. For this reason, a minimum vessel diameter of at least 8 to 9 mm is preferred [25,26]. Additionally, increased vessel depth, degree of femoral artery calcification, and iliofemoral tortuosity have been shown to be negative predictors of percutaneous TEVAR success [24]. All of these variables are readily evaluable with CTA and, in conjunction with sound clinical judgment, can be used to avoid the dreaded complication of iliac disruption necessitating open surgical repair. In cases of unfavorable anatomy, surgical or endovascular conduits have been shown to reliably facilitate endovascular repair [53]. The radiation dose associated with properly performed CT examinations in the evaluation of thoracic aortic disease is not of significant concern [54].


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Potential nephrotoxicity from iodinated contrast in patients with impaired renal function is the primary concern in this patient population, although the benefits of obtaining key diagnostic information typically outweigh the low risk of developing contrast-induced nephropathy [55]. Utilization of modern CT optimization techniques, such as high-pitch spiral CT imaging, low kilovolt (peak) imaging, wide-area detectors, and iterative reconstruction techniques, allows for lower volumes of contrast and lower radiation dose with adequate diagnostic image quality [39,56,57]. CT CT Unenhanced CT is useful for identification of aortic size, acute IMH, and aortic calcification. In conjunction with CTA, sensitivity for detection of IMH is as high as 96%, and sensitivity and specificity for detection of the intimal flap in aortic dissection approach 100% [11,39]. Moreover, unenhanced CT can delineate complications related to acute aortic syndromes such as mediastinal or pericardial hemorrhage and rupture. The addition of CTA allows for comprehensive assessment of other sequelae, including end-organ ischemia, acute aortic valvular insufficiency, intravascular thrombus, and supra-aortic, coronary, and mesenteric vascular involvement [25,39,58]. The use of contrast-enhanced CT and multiphase CT (without and with contrast) can provide similar information to CTA with regard to the anatomic extent of vascular pathology. Often, such studies are pursued to investigate other clinical questions or vague presentations and incidentally reveal significant vascular findings in the thoracic aorta. The lack of standard thin-section image acquisition, arterial-phase bolus timing, and 3-D renderings with these techniques is the principal limitation, and therefore CTA is the preferred imaging modality for the dedicated workup of thoracic aorta diseases [37,39].


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Thoracic Aorta Interventional Planning and Follow-Up MRA Similar to CT, magnetic resonance imaging (MRI) of the thoracic aorta can be performed with and without intravenous contrast. The principle advantage of MRI over CT is the lack of ionizing radiation, making it a particularly attractive imaging option in young patients. MRI is a more time-consuming study than CT, necessitating a stable patient. Importantly, MRI confers similar sensitivity and specificity as CTA and transesophageal echocardiography (TEE) for detection of dissection flaps, although like TEE it is less accurate for detection of branch vessel involvement [59]. There are a variety of unenhanced MRA techniques, including time of flight, phase-contrast imaging, ECG-gated fast spin-echo, and steady-state free precession (SSFP). SSFP, for example, has been shown to have equal accuracy for the assessment of aortic diameter compared with contrast-enhanced MRA (CE-MRA) [60]. The SSFP technique is also useful for visualization of dissection flaps [39]. General limitations with unenhanced MRA include loss of signal due to turbulent flow, long acquisition times, susceptibility to field inhomogeneity and motion, and the need for considerable patient cooperation for sequences requiring breath holding [36]. CE-MRA using 3-D spoiled gradient-echo sequences is the preferred MRI technique for thoracic aortic imaging, providing superior arterial signal, high spatial and contrast resolution, and rapid data acquisition during a single breath hold [36,39]. ECG gating may be added for motion-free evaluation of the ascending aorta and aortic root. Similar to the typical multiphasic CTA protocol, CE-MRA studies generally consist of unenhanced, arterial, and delayed-phase images. Various triggering methods can be used to ensure adequate gadolinium contrast opacification.


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Because the images are acquired in a near-isotropic fashion, similar multiplanar reformats to those used in CTA can be produced [39]. In addition to characterizing the extent of aortic pathology and providing precise, highly reproducible aortic measurements, CE-MRA has particular efficacy in delineation of mural thrombus versus intramural blood when CT results are equivocal [10,61]. It is also useful in the differentiation of aortic wall inflammation from intramural hemorrhage and atheroma [36]. A point of caution in the interpretation of MRA is to use source images for measurements, as maximum-intenstiy projection images may obscure the vessel wall and lead to underestimation of lumen size [10]. More advanced magnetic resonance (MR) applications allow flow mapping via time-resolved imaging techniques. Such techniques allow for the evaluation of abnormal vascular anatomy, atherosclerotic plaque burden, collateral blood flow, and hemodynamic parameters in the involved segment of aorta [36,39]. Although CE-MRA is preferred for the aforementioned reasons, certain situations exist in which unenhanced MRA is desirable. These include patients with poor intravenous access; advanced, dialysis-dependent renal failure with glomerular filtration rate <30 mL/min/1.73 m2 (because of the risk of nephrogenic systemic fibrosis); and pregnancy (because of the possible teratogenic effects of gadolinium-based contrast agents) [55,60,62]. Aortography Catheter angiography has largely been replaced by cross-sectional imaging in the evaluation of patients with suspected aortic pathology. An exception is in cases of coexisting malperfusion involving the coronary, visceral, or cerebral circulations. In such cases, angiography allows for evaluation and possible revascularization of the affected vascular bed along with further characterization of aortic pathology [45,61,63].


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Angiography has gained traction in the hybrid operating-room approach to acute type A aortic dissection, in which diagnostic and interventional angiography techniques are combined with open surgical repair [63]. Catheter angiography allows for assessment of luminal size of the iliofemoral system but is limited in its ability to assess for atherosclerotic plaque burden [56]. Additionally, digital subtraction angiography remains the gold standard for preintervention visualization of the artery of Adamkiewicz, an important consideration when there is high concern for spinal cord ischemia [64]. TEE and TTE In hemodynamically unstable patients, transthoracic echocardiography (TTE) is a useful imaging study for rapid evaluation of valvular function, aortic root dilation, and thoracic aortic dissection. This can be further supplemented with TEE, which allows for comparatively superior anatomic evaluation and can be left in place for intraoperative monitoring [61,65]. Although offering comparable sensitivities to CT and MRI for detection of thoracic aortic dissection, TEE is limited in its sensitivity for detection of branch vessel involvement and delineation of pathology below the gastroesophageal junction [59]. Echocardiography can also evaluate for concomitant cardiovascular disease and identify patients in whom coronary revascularization or valvular repair may be indicated [54,66]. Thoracic Aorta Interventional Planning and Follow-Up IVUS Similar to intraprocedural TEE, intravascular US (IVUS) is an additional adjunctive imaging tool that can aid in optimal visualization of intimal tears, ideal endograft positioning, assessment of branch vessel patency, and detection of abnormal flow within the false lumen and excluded aneurysm sac after endograft placement [67].


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. US In cases where thoracic aortic disease does not extend into the abdomen and no cross-sectional imaging of the iliofemoral system is available, US duplex Doppler of the iliofemoral arteries is useful for assessing adequate access. US duplex Doppler allows for assessment of vessel diameter and plaque burden along the anterior aspect of the vessel. In one recent series examining the use of US-guided femoral access in abdominal aortic endovascular aneurysm repair patients, intraoperative US guidance was shown to significantly reduce operative time and access wound complications [68]. Although similar dedicated studies are not available for TEVAR, the underlying principle is directly transferrable. Similarly, IVUS at the time of intervention has been shown to provide reliable information regarding iliofemoral morphology and atherosclerotic disease burden [56]. Radiography Chest radiographs will demonstrate abnormalities in a large percentage of patients with acute thoracic aorta pathology. For example, in patients presenting with acute aortic dissection, >80% demonstrated chest radiograph abnormalities, with mediastinal widening seen in just over 50% of cases [59,69]. However, radiography can only alert to an underlying abnormality and provides no specific information regarding type of pathology or detailed anatomic information necessary for interventional planning. FDG-PET/CT Nuclear medicine studies play a limited role in the workup of acute aortic pathology. In patients presenting with acute type B aortic dissection, greater uptake of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG) in the aortic wall as seen on positron emission tomography (PET)/CT has been shown to predict rupture and dissection propagation [70]. The optimal CTA protocol for TEVAR follow-up is not well defined. Most commonly a triphasic protocol is performed with acquisition of unenhanced, arterial, and delayed-phase (60-120 seconds after injection) imaging.


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. The utility of the unenhanced phase is to differentiate extraluminal calcification or postendoleak intervention material from extraluminal contrast seen on contrast-enhanced images. Although comprehensive, such a protocol delivers a high radiation dose. Some institutions employ a late delayed phase of 300 seconds to better visualize low-flow endoleaks [72]. With regard to endoleak, type I endoleaks occurring at the proximal (Ia) or distal (Ib) landing zones are the most common cause for reintervention following TEVAR, occurring in up to 15% of cases [75]. In contrast to abdominal aorta endovascular repair where type II endoleaks are most common, type II endoleaks occur in a small percentage of TEVAR patients, likely because of fewer patent collateral vessels in the thorax compared with the abdomen [76]. Furthermore, type II endoleaks are not associated with increased risk of thoracic aorta rupture and are often managed conservatively. Types III, IV, and V endoleaks occur much less frequently, with type III being the only subtype other than type I to require immediate therapy [72]. Thoracic Aorta Interventional Planning and Follow-Up It has been shown that luminal diameter as determined from 3-D measurements correlates well with aortic luminal area during the postoperative period and can be used as a proxy for luminal blood flow [77]. This applies to both true and false lumens in cases of dissection, although the relationship becomes less clear with large false lumen diameters because of the propensity for complex luminal configuration. Serial evaluation of true and false lumen diameters via CTA in the postintervention period is a marker for vascular remodeling. Recent midterm results from the VIRTUE Registry demonstrate similar rates of vascular remodeling in patients with uncomplicated acute and subacute type B dissections.


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Along with other studies demonstrating a mortality benefit in the treatment of subacute to chronic uncomplicated type B dissections, these data suggest that TEVAR is a viable alternative treatment option in the management of these patients compared with optimized medical therapy [12,33,34,78]. Partial false lumen thrombosis is an important predictor of regional luminal growth and reintervention rate. Although incompletely understood, this is postulated to be due to a regional increase in luminal pressure owing to small diameter [79]. Chronic dissections tend to show lesser degrees of remodeling, perhaps because of the frequent presence of multiple intimal tears and development of intercostal collaterals in these patients [14,80]. When there is a question of false lumen thrombosis status, the absence of contrast enhancement on arterial and early delayed-phase CTA does not necessarily indicate complete thrombosis given the possibility of a low-flow state. In such cases, more-delayed imaging demonstrates higher sensitivity for detection of partial thrombosis [81]. Similar to the findings seen in TEVAR for aortic dissection, there is significant vascular remodeling when TEVAR is used for IMH or PAU, with near-complete normalization of aortic diameter at 1 year as measured on CTA [13,82]. CTA is also the preferred imaging modality of choice for evaluation of endograft infection, one of the most serious complications after TEVAR. A recent study demonstrated that in the small number of patients with an infected endograft, CTA suggested the diagnosis in 78% of cases, with the most common findings being periaortic inflammation and erosion into surrounding structures [83]. The principle disadvantages of CTA in the follow-up period are potential nephrotoxicity and cumulative radiation dose, particularly in younger patients.


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. A study evaluating radiation exposure during TEVAR and subsequent follow-up found that cumulative lifetime radiation exposure in these patients is likely to exceed 350 mSv, conferring an increased lifetime risk of at least 2.7% for developing solid-organ malignancy or leukemia [84]. The development of ever-advanced iterative reconstruction algorithms permits the use of lower tube energies, thereby allowing for reduced patient radiation exposure. A recent study highlighted radiation dose reductions ranging from 63% to 69% at standard kilovolt (peak) using a fully iterative reconstruction algorithm as compared with standard filtered back-projection without appreciable changes in conspicuity of endoleaks or in-stent thrombosis [85]. Dual-energy acquisition offers the possibility of eliminating the unenhanced phase via the creation of a virtual noncontrast image set. Another recent study demonstrated near-perfect correlation between single- and dual-phase dual-energy scans in comparison with a traditional three-phase protocol, with 19.5% and 64.1% less radiation exposure, respectively [72]. CT CT Although not ideal given the inability to directly detect endoleaks, unenhanced CT can still offer valuable follow- up information in TEVAR patients with chronic renal insufficiency and stent grafts not amenable to MRA. Unenhanced CT is useful in the assessment of graft migration, aortic rupture, and delineation of vascular calcifications, hematoma, and surgical material that could otherwise be confused for endoleak on CTA examinations [36]. Additionally, by using aneurysm sac diameter as a proxy for graft and anastomotic integrity, unenhanced CT can indirectly suggest endoleak if sac volume increases over time by more than 2% [86]. In patients with stable findings on early postintervention imaging and a low risk of graft complications, follow-up with unenhanced CT complemented by CTA when questions arise may be a viable strategy.


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. MRA MRA MRI after TEVAR suffers from severe susceptibility to artifacts relating to the stainless steel used in many stent graft types, obscuring surrounding relevant anatomy and limiting evaluation for endoleak [39,84]. One particular Thoracic Aorta Interventional Planning and Follow-Up group in which MRI is a preferred imaging modality is patients in whom nitinol stents are placed. This is because these endografts do not produce susceptibility artifacts, thereby allowing adequate visualization of the underlying vasculature [74]. Various studies have demonstrated comparable to superior sensitivities in detection of endoleak with MRA compared with CTA when such stents are used [87,88]. Additional research has shown that in patients with MR-compatible endografts, unenhanced MRA can reliably assess stent position and geometry, whereas CE- MRA can sufficiently evaluate endograft hemodynamics and aortic diameter [89]. A principal advantage of MRI in the follow-up period is its lack of ionizing radiation. In younger patients in whom cumulative radiation dose from repeat CT examinations is of particular concern, placement of an MR- compatible endograft should strongly be considered so that routine MRI surveillance can be obtained [61]. As noted previously, the use of CE-MRA is limited in cases of severe renal dysfunction and pregnancy. Aortography Given its invasiveness, catheter angiography is not a routine surveillance tool after TEVAR. However, in cases where significant endoleaks are identified on cross-sectional imaging or where the origin of endoleak is unclear, catheter angiography is indispensable for further anatomic characterization as well as definitive treatment [76]. TEE and TTE In cases where the extent of residual aortopathy is confined to the aortic root or proximal aorta dilation, TTE may play an adjunctive surveillance role, reducing the frequency of CT or MR surveillance [61].


Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. TEE provides suboptimal evaluation of suspected endoleak and should be considered only in patients in whom CTA is precluded because of severe renal dysfunction or contrast allergy [84]. US US US duplex Doppler is an alternative modality for follow-up of abdominal aortic endovascular aneurysm repair with high specificity for detection of endoleaks and high accuracy for evaluation of aneurysm sac size. The addition of contrast material makes US an even more sensitive and specific test than CTA for characterization of endoleaks [90]. Its use in TEVAR is impractical in the chest given poor acoustic windows but may provide diagnostic information for the abdominal aspect of the stent graft [38]. Radiography Radiography in the postintervention period has traditionally been used to evaluate for stent migration and integrity [71]. However, given ever-increasing improvements in CT imaging quality as well as the low incidence of stent graft fractures with currently available endograft devices, the utility of radiographic follow-up is increasingly limited [38]. surveillance interval is unclear and may be procedure and patient specific. In the postintervention follow-up evaluation, CTA is the imaging modality of choice, given its sensitivity for the detection of endoleaks, changes in aortic/aneurysm diameter, evaluation of false lumen thrombosis, and Thoracic Aorta Interventional Planning and Follow-Up assessment for device migration and integrity. MRA can provide equivalent information and is preferred for long-term follow-up of younger patients given the lack of ionizing radiation, but it can be used only with MR- compatible stent grafts. Although there are references that report on studies with design limitations, 37 well-designed or good-quality studies provide good evidence. Relative Radiation Level Designations 30-100 mSv 10-30 mSv


Head Trauma PCAs

Head Trauma PCAs.  Introduction/Background Head trauma (ie, head injury) is a significant public health concern and is a leading cause of morbidity and mortality in children and young adults. According to the Centers for Disease Control and Prevention, head trauma resulted in over 2.5 million emergency department (ED) visits in the United States in 2014 (63% increase from 2006) with nearly 290,000 hospitalizations and 57,000 deaths [1]. Common mechanisms of injury include falls, motor vehicle accidents, and acts of violence. Athletic and military personnel are additionally susceptible to sport- and blast- related exposures. Many individuals seek medical attention after a disruption in the normal function of the brain (eg, concussions with transient loss of consciousness [LOC] or post-traumatic amnesia [PTA]); these cases would meet the definition of a traumatic brain injury (TBI). OR aUniformed Services University, Bethesda, MarylandbPanel Chair, Montefiore Medical Center, Bronx, New York. cOhio State University, Columbus, Ohio. dDuke University School of Medicine, Durham, North Carolina; American College of Emergency Physicians. eOttawa Hospital Research Institute and the Department of Radiology, The University of Ottawa, Ottawa, Ontario, Canada; Canadian Association of Radiologists. fMayo Clinic, Rochester, Minnesota. gUniversity of New Mexico, Albuquerque, New Mexico; American College of Physicians. hUniversity of California Los Angeles, Los Angeles, California. iEinstein Healthcare Network, Philadelphia, Pennsylvania. jUniversity of California Los Angeles, Los Angeles, California; American Academy of Neurology. kOregon Health & Science University, Portland, Oregon. lLittleton Adventist Hospital, Littleton, Colorado; Neurosurgery expert. mR. Adams Cowley Shock Trauma Center, University of Maryland Medical Center, Baltimore, Maryland. nJohn H. Stroger, Jr. Hospital of Cook County, Chicago, Illinois; Neurosurgery expert.


Head Trauma PCAs

Head Trauma PCAs. oAlbert Einstein College of Medicine Montefiore Medical Center, Bronx, New York, Internal Medicine Physician. pWeill Cornell Medicine, New York, New York. qColumbia University Medical Center, New York, New York. rUniversity of Cincinnati Medical Center, Cincinnati, Ohio. sSpecialty Chair, Atlanta VA Health Care System and Emory University, Atlanta, Georgia. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. *The views expressed in this manuscript are those of the author and do not reflect the official policy of the Department of the Army/Navy/Air Force, Department of Defense, or United States Government. Reprint requests to: publications@acr.org Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the initial imaging evaluation of acute head trauma. Head Trauma CTA Head and Neck There is no relevant literature to support the use of CT angiography (CTA) in the initial imaging evaluation of acute head trauma without suspected vascular injury (see Variants 8 and 9 when suspected). FDG-PET/CT Brain There is no relevant literature to support the use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT in the initial imaging evaluation of acute head trauma. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography (SPECT) or SPECT/CT in the initial imaging evaluation of acute head trauma. MR Spectroscopy Head There is no relevant literature to support the use of MR spectroscopy (MRS) in the initial imaging evaluation of acute head trauma.


Head Trauma PCAs

Head Trauma PCAs. MRA Head and Neck There is no relevant literature to support the use of MR angiography (MRA) in the initial imaging evaluation of acute head trauma. MRI Functional (fMRI) Head There is no relevant literature to support the use of functional MRI (fMRI) in the initial imaging evaluation of acute head trauma. MRI Head There is no relevant literature to support the use of MRI in the initial imaging evaluation of acute head trauma (please see Variant 4 for discussion of MRI after negative head CT). MRI Head with DTI There is no relevant literature to support the use of diffusion tensor imaging (DTI) in the initial imaging evaluation of acute head trauma. Radiography Skull There is no relevant literature to support the use of radiographs in the initial imaging evaluation of acute head trauma (replaced by CT, which is more sensitive for neurosurgical lesions). Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the initial imaging evaluation of acute head trauma. Head Trauma military personnel, per Department of Defense guidelines, a positive CT would prompt reclassification from mild to moderate TBI [18]. In the vast majority of these patients, CT will be negative for acute traumatic findings, so patients can be safely discharged rather than admitted as long as the neurologic examination is also normal (negative predictive value of 100% for neurologic deterioration requiring surgical intervention) [19]. One analysis quantified the risk of deterioration with both normal CT and neurologic examination as very low (0.006%), recommending discharge regardless of whether there was a responsible adult available to observe the patient [7]. It is important for mild TBI discharge instructions to be provided in written form; they should discuss why or when to return to the ED, plus educational information on postconcussive symptoms [20].


Head Trauma PCAs

Head Trauma PCAs. CTA Head and Neck There is no relevant literature to support the use of CTA in the initial imaging evaluation of acute head trauma without suspected vascular injury (see Variants 8 and 9 when suspected). FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the initial imaging evaluation of acute head trauma. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the initial imaging evaluation of acute head trauma. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the initial imaging evaluation of acute head trauma. MRA Head and Neck There is no relevant literature to support the use of MRA in the initial imaging evaluation of acute head trauma. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the initial imaging evaluation of acute head trauma. MRI Head There is no relevant literature to support the use of MRI in the initial imaging evaluation of acute head trauma (please see Variant 4 for discussion of MRI after negative head CT). MRI Head with DTI There is no relevant literature to support the use of DTI in the initial imaging evaluation of acute head trauma. Radiography Skull There is no relevant literature to support the use of radiographs in the initial imaging evaluation of acute head trauma (replaced by CT, which is more sensitive for neurosurgical lesions). Head Trauma Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the initial imaging evaluation of acute head trauma. CT Head Head CT is useful for the evaluation of moderate, severe, or penetrating acute head trauma. Multiplanar reformatted images have been shown to increase diagnostic accuracy and should be included [16,17].


Head Trauma PCAs

Head Trauma PCAs. Overall, a normal CT tends to be associated with better outcomes than an abnormal CT, and in one study of 72 patients without systemic injury, focal hemorrhages >4.1 mL predicted a 2-fold greater risk of a poor outcome than patients with smaller lesions [31]. In the setting of penetrating head trauma, most commonly gunshot wounds (including self-inflicted), only 10% survive to reach the hospital, where morbidity and mortality remain extremely high. CT findings associated with an especially poor prognosis include brain stem and bilateral hemispheric injuries [30]. Traditional CT scoring systems for ICH and mass effect (eg, Marshall, Rotterdam) have been shown to predict mortality in moderate to severe head trauma. The NeuroImaging Radiological Interpretation System is a more recently developed CT scoring system, which uses standardized terminology from the National Institutes of Health common data elements for TBI imaging and which offers improved prediction of clinical disposition and management in TBI patients (ie, who will need prolonged admissions or neurosurgical procedures), beyond prediction of mortality alone [32,33]. CTA Head and Neck There is no relevant literature to support the use of CTA in the initial imaging evaluation of acute head trauma without suspected vascular injury (see Variants 8 and 9 when suspected). Please refer to discussion under Variants 8 and 9 on clinical risk factors that are associated with intracranial vascular injury and would support the use of CTA/CT venography (CTV). FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the initial imaging evaluation of acute head trauma. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the initial imaging evaluation of acute head trauma. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the initial imaging evaluation of acute head trauma.


Head Trauma PCAs

Head Trauma PCAs. MRA Head and Neck There is no relevant literature to support the use of MRA in the initial imaging evaluation of acute head trauma. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the initial imaging evaluation of acute head trauma. MRI Head There is no relevant literature to support the use of MRI in the initial imaging evaluation of acute head trauma (please see Variant 4 for discussion of MRI after negative head CT). MRI Head with DTI There is no relevant literature to support the use of DTI in the initial imaging evaluation of acute head trauma. Radiography Skull There is no relevant literature to support the use of radiographs in the initial imaging evaluation of acute head trauma (replaced by CT, which is more sensitive for neurosurgical lesions). Head Trauma Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the short-term follow-up imaging evaluation of acute head trauma. There is some controversy about the necessity, with other guidelines recommending against routine repeat CT in the presence of a normal initial CT and in the absence of neurologic deterioration [2]. A single-center 2-year retrospective study of 2,444 ED patients with head trauma of varying severity and a negative head CT (80.8% of all scans) found a very low rate (1 case or 0.04%) of intracranial complications within 72 hours. Of the discharged patients (74.1%), <1% returned to the ED and received a repeat CT (all negative). Of the admitted patients (25.9%), <10% received a repeat CT, with only one positive for a small parietal lobe contusion, which was not visible on the initial CT and did not require neurosurgical intervention [34]. There is also some controversy about the necessity of routine observation and repeat CT in head trauma patients with coagulopathy and a normal initial CT.


Head Trauma PCAs

Head Trauma PCAs. One prospective cohort study of 859 older adults (>55 years of age) with head trauma and a negative CT found a very low rate (3 cases or 0.3%) of delayed traumatic ICH within 14 days, and only 1 of the 3 cases occurred in a patient on anticoagulant or antiplatelet medication (warfarin with a positive repeat CT at 5 days) [35]. The authors conclude the risk of delayed ICH is low, even on anticoagulant or antiplatelet medication, and does not merit routine observation and repeat CT; however, the study is limited by the small number of patients in each anticoagulant and antiplatelet group. CTA Head and Neck There is no relevant literature to support the use of CTA in the short-term follow-up imaging evaluation of acute head trauma without suspected vascular injury (see Variants 8 and 9 when suspected). FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the short-term follow-up imaging evaluation of acute head trauma. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the short-term follow-up imaging evaluation of acute head trauma. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the short-term follow-up imaging evaluation of acute head trauma. Head Trauma MRA Head and Neck There is no relevant literature to support the use of MRA in the short-term follow-up imaging evaluation of acute head trauma. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the short-term follow-up imaging evaluation of acute head trauma. MRI Head Although brain MRI is not the most useful initial imaging modality for the evaluation of acute head trauma, it may be indicated as a follow-up study when there are persistent neurologic deficits that remain unexplained after the head CT [2]. MRI is more sensitive than CT for subtle findings adjacent to the calvarium or skull base (eg, small cortical contusions and subdural hematomas) [29].


Head Trauma PCAs

Head Trauma PCAs. It is also more sensitive for small white matter lesions in traumatic or diffuse axonal injury (DAI). Only 10% of DAI is positive on CT because >80% of lesions are not associated with macroscopic hemorrhage and therefore have a higher chance of detection on MRI using a combination of T2-weighted, T2*-weighted, and diffusion-weighted images [18]. There is some controversy about the necessity of MRI in the acute phase. A single-center 2-year retrospective study of all TBI patients with both CT and MRI in the acute phase found MRI to be more sensitive for small intracranial lesions, especially shearing injuries (DAI), which could be of prognostic value in patients with unexplained poor GCS scores. However, none of these additional findings affected management plans in the acute phase [36]. A single-center 3-year prospective study of all TBI patients with both CT and MRI in the acute phase also found MRI to be more sensitive for subtle contusions, shearing injuries, and extra-axial hematomas (33% of cases). Once again, the additional information did not affect management in the acute phase [37]. If the clinical focus has transitioned from short-term management to long-term prognostication in the acute phase, then an early MRI may be of greater value, particularly in patients who have mild TBI with normal CTs (approximately 15% will have persistent neurocognitive sequelae at 1 year). A prospective Level 1 trauma multicenter study has found that approximately 27% of patients who have mild TBI with normal CTs show abnormalities on early MRI (eg, small cortical contusions or hemorrhagic axonal injury) and that these findings may be clinically relevant in improving prediction of 3-month outcomes [38]. There is ongoing research in the utility of blood-based biomarkers (eg, GFAP) to determine which patients who have mild TBI and negative CT were more likely to benefit from MRI [39].


Head Trauma PCAs

Head Trauma PCAs. MRI Head with DTI There is no relevant literature to support the use of DTI in the short-term follow-up imaging evaluation of acute head trauma. Radiography Skull There is no relevant literature to support the use of radiographs in the short-term follow-up imaging evaluation of acute head trauma. Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the short-term follow-up imaging evaluation of acute head trauma. CT Head In the presence of an abnormal initial CT and in the absence of neurologic deterioration, the decision to perform a routine repeat CT should depend on the estimated risk for subclinical progression of intracranial findings. A large systematic review and meta-analysis of 41 studies enrolling 10,501 patients with TBI suggested there is overutilization of repeat CT, which changed management in only 11.4% of patients across prospective studies and 9.6% of patients across retrospective studies (2.3% and 3.9% in a subgroup analysis of patients with mild TBI) [40]. Head Trauma Routine follow-up CT after an abnormal initial CT is supported for moderate to severe TBI and for anticoagulated patients [2]. Patients on anticoagulant or antiplatelet medication had a 3-fold increase in frequency of bleeding progression on repeat head CT (26% versus 9%) in one retrospective analysis of 508 CT-positive TBIs [41]. For patients with mild TBI and positive CT (who are not on anticoagulation), the appropriateness of routine repeat CT may depend on the size and type of intracranial findings. A retrospective review of 321 patients with mild TBI with ICH on initial CT found imaging progression in only 6% (and neurologic deterioration in only 1%). Subfrontal/temporal parenchymal contusion and volume of ICH >10 mL were imaging predictors of progression (use of anticoagulation and >65 years of age were clinical predictors).


Head Trauma PCAs

Head Trauma PCAs. Based on outcomes analysis, the authors conclude that patients with mild TBI with a small convexity contusion or extra-axial hemorrhage <10 mL do not require routine repeat CT or admission to the intensive care unit in the absence of neurologic deterioration [42]. In the presence of an abnormal initial CT, other patient factors such as intoxication or pharmacologic sedation often affect the reliability of serial examinations in the acute trauma setting and lower the threshold for follow-up imaging, even in the absence of neurologic deterioration. CTA Head and Neck There is no relevant literature to support the use of CTA in the short-term follow-up imaging evaluation of acute head trauma without suspected vascular injury (see Variants 8 and 9 when suspected). Please refer to discussion under Variants 8 and 9 on imaging risk factors that are associated with intracranial vascular injury and would support the use of CTA/CTV. FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the short-term follow-up imaging evaluation of acute head trauma. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the short-term follow-up imaging evaluation of acute head trauma. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the short-term follow-up imaging evaluation of acute head trauma. MRA Head and Neck There is no relevant literature to support the use of MRA in the short-term follow-up imaging evaluation of acute head trauma. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the short-term follow-up imaging evaluation of acute head trauma. MRI Head Although brain MRI is not the most useful initial imaging modality for the evaluation of acute head trauma, it may be indicated as a follow-up study when there are persistent neurologic deficits that remain unexplained after the head CT [2].


Head Trauma PCAs

Head Trauma PCAs. MRI is more sensitive than CT for subtle findings adjacent to the calvarium or skull base (eg, small cortical contusions and subdural hematomas) [29]. It is also more sensitive for small white matter lesions in traumatic axonal injury or DAI. Only 10% of DAI is positive on CT because >80% of lesions are not associated with macroscopic hemorrhage and therefore have a higher chance of detection on MRI using a combination of T2- weighted, T2*-weighted, and diffusion-weighted images [18]. There is some controversy about the necessity of MRI in the acute phase. A single-center 2-year retrospective study of all patients with TBI who underwent both CT and MRI in the acute phase found MRI to be more sensitive for small intracranial lesions, especially shearing injuries (DAI), which could be of prognostic value in patients with unexplained poor GCS scores. However, none of these additional findings affected management plans in the acute phase [36]. A single-center 3-year prospective study of all patients with TBI who underwent both CT and MRI in the acute phase also found MRI to be more sensitive for subtle contusions, shearing injuries, and extra-axial hematomas (33% of cases). Once again, the additional information did not affect management in the acute phase [37]. Head Trauma MRI Head with DTI There is no relevant literature to support the use of DTI in the short-term follow-up imaging evaluation of acute head trauma. Radiography Skull There is no relevant literature to support the use of radiographs in the short-term follow-up imaging evaluation of acute head trauma. Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the short-term follow-up imaging evaluation of acute head trauma. CT Head Head CT is useful for the evaluation of any trauma patient with neurologic deterioration, especially in the acute setting and regardless of whether the initial imaging was positive or negative [2].


Head Trauma PCAs

Head Trauma PCAs. CT is highly sensitive for the detection of findings that may require neurosurgical intervention (eg, new or worsening hemorrhage, herniation, and hydrocephalus). Multiplanar reformatted images have been shown to increase diagnostic accuracy and should be included [16,17]. In patients with a positive initial CT, reported predictors of imaging progression include subfrontal/temporal parenchymal contusion, volume of ICH >10 mL, use of anticoagulation, and >65 years of age [42]. In patients with a negative initial CT, delayed ICH is a rare but possible complication (overall incidence <0.5%) [35]. CTA Head and Neck There is no relevant literature to support the use of CTA in the short-term follow-up imaging evaluation of acute head trauma without suspected vascular injury (see Variants 8 and 9 when suspected). FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the short-term follow-up imaging evaluation of acute head trauma. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the short-term follow-up imaging evaluation of acute head trauma. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the short-term follow-up imaging evaluation of acute head trauma. MRA Head and Neck There is no relevant literature to support the use of MRA in the short-term follow-up imaging evaluation of acute head trauma. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the short-term follow-up imaging evaluation of acute head trauma. MRI Head Head CT is the most useful follow-up imaging modality for the evaluation of any trauma patient with neurologic deterioration, especially in the acute setting, and regardless of whether the initial imaging was positive or negative [2]. Brain MRI may be indicated as a second-line study when there are persistent neurologic deficits that remain unexplained after the head CT.


Head Trauma PCAs

Head Trauma PCAs. MRI is more sensitive than CT for subtle findings adjacent to the calvarium or skull base (eg, small cortical contusions and subdural hematomas) [29]. MRI is also more sensitive for small white matter Head Trauma lesions in traumatic axonal injury or DAI. MRI with diffusion-weighted imaging can detect acute ischemic stroke (specifically infarct core) with higher sensitivity than head CT. There is some controversy about the necessity of MRI in the acute phase. A single-center 2-year retrospective study of all patients with TBI who underwent both CT and MRI in the acute phase found MRI to be more sensitive for small intracranial lesions, especially shearing injuries (DAI), which could be of prognostic value in patients with unexplained poor GCS scores. However, none of these additional findings affected management plans in the acute phase [36]. A single-center 3-year prospective study of all patients with TBI who underwent both CT and MRI in the acute phase also found MRI to be more sensitive for subtle contusions, shearing injuries, and extra-axial hematomas (33% of cases). Once again, the additional information did not affect management in the acute phase [37]. MRI Head with DTI There is no relevant literature to support the use of DTI in the short-term follow-up imaging evaluation of acute head trauma. Radiography Skull There is no relevant literature to support the use of radiographs in the short-term follow-up imaging evaluation of acute head trauma. Variant 7: Subacute or chronic head trauma with unexplained cognitive or neurologic deficit(s). Initial imaging. As noted in the introduction/background section, head trauma is a significant public health concern and is also a leading cause of morbidity and mortality in children and young adults, especially in the setting of moderate, severe, or penetrating head trauma.


Head Trauma PCAs

Head Trauma PCAs. Even mild head trauma, which accounts for >75% of cases, can be associated with a significant risk of persistent neurocognitive/postconcussive symptoms, affecting approximately 58% at 1 month and 15% at 1 year after injury (postconcussive syndrome is defined as >3 months) [20]. There has been increasing recognition of the chronic sequelae from repetitive concussions (mild TBI) in athletic and military personnel, which can lead to neurodegenerative disease in some cases (chronic traumatic encephalopathy) [2]. A survey of 2,525 infantry soldiers returning from Operations Iraqi Freedom and Enduring Freedom found that 15% reported experiencing events associated with mild TBI, which has been termed a signature injury of those conflicts (80% secondary to improvised explosive devices) [18]. Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the initial imaging evaluation of subacute or chronic head trauma with unexplained cognitive or neurologic deficit(s). CT Head Although head CT is the most useful initial imaging for the evaluation of acute head trauma, brain MRI is typically recommended as the most useful initial imaging for the evaluation of subacute or chronic head trauma, when rapid detection of acute ICH and neurosurgical lesions is no longer the primary clinical focus. MRI is more sensitive than CT for subtle findings adjacent to the calvarium or skull base (eg, focal encephalomalacia at the inferior frontal or anterior temporal lobes as chronic sequelae of previous contusions). It is also more sensitive for small white matter lesions (microbleeds) as chronic sequelae of previous traumatic axonal injury or DAI, which may help to explain persistent cognitive or neurologic deficit(s) [32]. CT is a valid option when there is a specific question that does not require the high soft-tissue contrast resolution of MRI (eg, possible shunt failure in chronic severe TBI).


Head Trauma PCAs

Head Trauma PCAs. It is also a valid option for patients who present in a delayed fashion after head trauma (eg, gradual decline after a fall due to subacute or chronic subdural hematoma). Head Trauma CTA Head and Neck There is no relevant literature to support the use of CTA in the initial imaging evaluation of subacute or chronic head trauma with unexplained cognitive or neurologic deficit(s) unless there is also suspected intracranial vascular injury (see Variants 8 and 9 when suspected). FDG-PET/CT Brain FDG is the most widely used PET radiopharmaceutical and is a glucose analog. Glucose is the primary energy source for the brain; therefore, FDG uptake on PET is a marker of local metabolism, which is closely coupled to local neuronal activity and can be quantified as the cerebral metabolic rate of glucose [18]. In normally functioning brain tissue, local metabolism is also closely coupled to perfusion; therefore, findings on metabolic PET imaging will often (but not always) parallel findings on perfusion SPECT imaging [32]. In acute severe TBI with brain contusion, FDG-PET has found both pericontusion and distant/global hypometabolism, whereas in chronic mild TBI, FDG-PET has found regional hypometabolism that may correlate with cognitive and behavioral impairments [18]. One study in combat veterans with chronic postconcussive syndrome found hypometabolism in the infratentorial and medial temporal regions, which may be unique to blast exposures [44]. Aside from FDG, other research studies have used oxygen (15O), neuronal ([11C] flumazenil), inflammation ([11C] PK11195), amyloid ([11C] PiB), and tau ([18F] T807) radiopharmaceuticals [18]. Despite the promise of molecular imaging for advancing our understanding of TBI pathophysiology, there is insufficient evidence to support the routine clinical use of PET at the individual patient level [45].


Head Trauma PCAs

Head Trauma PCAs. HMPAO SPECT or SPECT/CT Brain Although SPECT is used clinically with a wide variety of radiopharmaceuticals, brain SPECT most commonly refers to cerebral perfusion or blood flow imaging using either Tc-99m-hexamethylpropyleneamine oxime or Tc- 99m-ethyl cysteinate dimer. Measurement of regional cerebral blood flow is also an indicator of metabolic or neuronal activity; therefore, SPECT is utilized in epilepsy or neurodegenerative disorders in addition to cerebrovascular diseases. Other radiopharmaceuticals (eg, imaging of benzodiazepine or dopamine receptors) are generally confined to research studies. Perfusion SPECT is potentially a complementary tool to conventional CT/MRI and has been applied in research studies on mild, moderate, and severe TBI to identify additional lesions (eg, regional cerebral blood flow deficits) beyond anatomic imaging [18]. A study using early subacute SPECT in patients with mild to moderate TBI found that severe hypoperfusion was an independent predictor of unfavorable outcomes at 3 months; conversely, a normal initial SPECT has been shown to have high negative predictive value for persistent clinical deficits at 12 months [46]. Despite the promise of perfusion imaging (whether employing SPECT or CT/MRI-based techniques) for the detection of functional injury that may be occult on structural imaging, there is insufficient evidence to support the routine clinical use of SPECT at the individual patient level [45]. MR Spectroscopy Head MRS measures very small differences in the precessional frequencies of proton nuclei in order to differentiate their molecular environments (chemical shift effect). Single-voxel versus multi-voxel spectroscopy offers different strengths and weaknesses in signal-to-noise ratio versus spatial coverage; both have lower spatial resolution than other MRI-based techniques.


Head Trauma PCAs

Head Trauma PCAs. Commonly detected brain metabolites at intermediate (TE = 144 ms) to long (TE = 288 ms) echo time include N-acetylaspartate for neuronal integrity, creatine for cellular energy, choline for membrane turnover, and lactate for anaerobic metabolism. MRS at short (TE = 35 ms) echo time can further detect glutamate/glutamine for excitatory brain injury and myo-inositol for astroglial proliferation. The most commonly reported finding in the setting of head trauma is a reduction in N-acetylaspartate or N-acetylaspartate/creatine, sometimes accompanied by an elevation in choline and sometimes in otherwise normal-appearing brain, which may reflect microscopic DAI and/or Wallerian degeneration [32,45,46]. A study in concussed athletes found that decreased N-acetylaspartate/creatine took a longer time to resolve than the symptoms, suggesting that metabolic recovery is slower than clinical recovery [18]. Despite the interesting findings in MRS research, there is insufficient evidence to support the routine clinical use of MRS at the individual patient level [45]. MRA Head and Neck There is no relevant literature to support the use of MRA in the initial imaging evaluation of subacute or chronic head trauma with unexplained cognitive or neurologic deficit(s). Head Trauma MRI Head Brain MRI is the most useful initial imaging for the evaluation of subacute or chronic head trauma with unexplained cognitive or neurologic deficit(s). Conventional MRI will include a combination of T1-weighted, T2-weighted, T2*-weighted (gradient-echo), and diffusion-weighted imaging. It is more sensitive than CT for subtle findings adjacent to the calvarium or skull base (eg, focal encephalomalacia at the inferior frontal or anterior temporal lobes as chronic sequelae of previous contusions). It is also more sensitive for small white matter lesions (microbleeds) as chronic sequelae of previous traumatic axonal injury or DAI, although it is still far less sensitive than neuropathological investigation (microscopic analysis) [32].


Head Trauma PCAs

Head Trauma PCAs. Susceptibility-weighted imaging is a high-resolution 3-D T2*-weighted sequence that uses both magnitude and phase information to increase sensitivity for paramagnetic blood products (eg, pediatric TBI studies have detected 6 times as many microbleeds with susceptibility-weighted imaging than with older gradient-echo T2*-weighted sequences) [18]. In addition to detecting subtle structural injury, conventional MRI may help with the prognostication of long-term neurocognitive sequelae. Regarding mild head trauma, a prospective Level 1 trauma multicenter study found that abnormalities on early subacute MRI (eg, small cortical contusions or hemorrhagic axonal injury) are clinically relevant in improving prediction of 3-month outcomes [38]. Another prospective study in patients with mild TBI found a correlation between frontal-temporal-parietal microbleeds on early MRI susceptibility-weighted imaging and the presence or absence of depressive symptoms at 1 year after injury [50]. Regarding moderate to severe head trauma, one study found DAI on subacute MRI in almost three-quarters of patients who survived the acute phase, and only in those patients was GCS score (which tended to be lower) related to 12-month outcomes. It also found similar outcomes for DAI Stage 1 (lobar white matter lesions only) and DAI Stage 2 (callosal lesions), with poor outcomes for DAI Stage 3 (dorsolateral brain stem lesions) [51]. Another study on subacute MRI in post-TBI vegetative states found that depth/stage of DAI lesions helps predict recovery or nonrecovery at 1 year [52]. There is no relevant literature to support the added value or routine use of contrast-enhanced brain MRI instead of noncontrast brain MRI in the initial imaging evaluation of subacute or chronic head trauma. MRI Head with DTI Diffusion-weighted imaging generates a scalar coefficient for each voxel, which represents the average or mean diffusivity (mm2/s) of the water molecules in that location.


Head Trauma PCAs

Head Trauma PCAs. DTI applies the diffusion-sensitizing gradients in many (at least 6) different directions in order to generate a second-order tensor that characterizes directionality of water molecule diffusion. This can be visualized as a diffusion ellipsoid, where the long axis represents axial diffusivity, and the short axes represent radial diffusivity. An important summary measure of the degree of asymmetry between the long and short axes is fractional anisotropy. Fractional anisotropy is higher in white matter than gray matter or CSF because of its microstructure (fiber-tract architecture); therefore, fractional anisotropy has been studied extensively as a potential marker of axonal integrity, especially in the setting of persistently symptomatic mild TBI [18]. Multiple studies have shown regions of decreased fractional anisotropy and increased mean diffusivity in patients with mild, moderate, and severe TBI, as compared with healthy controls [53]. Other DTI studies performed in the early subacute phase have shown paradoxically increased fractional anisotropy, which has been attributed to cytotoxic edema or to postinjury repair [54,55]. Overall, there is significant heterogeneity in fractional anisotropy measurements among both TBI and healthy subjects, with published data based primarily upon group-level analyses. Despite continuing improvements in scanner gradients and diffusion techniques (eg, intravoxel resolution Head Trauma of crossing fibers), there is insufficient evidence to support the routine clinical use of DTI at the individual patient level [45]. Radiography Skull There is no relevant literature to support the use of radiographs in the initial imaging evaluation of subacute or chronic head trauma with unexplained cognitive or neurologic deficit(s). Variant 8: Head trauma with suspected intracranial arterial injury due to clinical risk factors or positive findings on prior imaging.


Head Trauma PCAs

Head Trauma PCAs. The reported incidence of blunt cerebrovascular injury (BCVI) has increased from approximately 0.1% to 1.0% of patients with closed head/neck trauma, with increased screening of asymptomatic patients. Symptomatic patients will have developed secondary strokes, which are associated with significant morbidity of up to 80% and mortality of up to 40% [56]. There is a variable latent period between vascular injury and symptom onset, with 17% to 36% developing symptoms >24 hours after injury, and when screening appropriately based on clinical or imaging risk factors, approximately 52% to 79% of patients with detected BCVI are asymptomatic [57]. Cerebrovascular injury is also a potential concern in the less common setting of penetrating head/neck trauma. In addition to indirect evidence of arterial injury on prior imaging (eg, hemorrhage or infarct), BCVI has a known association with head/face and cervical fractures. For example, with regard to intracranial arterial injury, positive imaging findings of a skull base fracture that involves the carotid canal or abnormal enlargement of the superior ophthalmic vein and cavernous sinus should prompt evaluation for a petrous or cavernous internal carotid artery injury, respectively [58]. Above the level of the skull base, the branches of the middle and anterior cerebral arteries are often at risk in the setting of penetrating head trauma [30]. Regarding clinical risk factors for BCVI, there are various screening criteria available, which involve tradeoffs in sensitivity (ranging between 63% and 84%) and positive predictive value or screening yield (ranging between 6% and 29%), similar to the clinical decision rules for selective CT scanning in mild head trauma [57]. The 2 original clinical decision rules were the Denver criteria (from University of Colorado) and the Memphis criteria (from University of Tennessee).


Head Trauma PCAs

Head Trauma PCAs. Both have since been broadened into the modified Denver criteria and the modified Memphis criteria, with the more recently introduced Boston criteria being based on the modified Denver criteria. For clinicians or providers who are not currently committed to a screening criteria for BCVI, one simple option is the 2010 guidelines from the Eastern Association for the Surgery of Trauma [56]: Arteriography Cervicocerebral Although catheter angiography is the historical reference standard and offers the highest spatial/temporal resolution for imaging evaluation of vascular pathology, noninvasive CTA is faster, has fewer safety concerns, and is most useful in the initial imaging evaluation of suspected intracranial arterial injury [45]. With modern CT equipment, accuracy has been shown to be comparable. One prospective study of 146 trauma patients who received both catheter angiography and CTA (16-slice multidetector-row) reported the latter to have a sensitivity of 97.7% and a specificity of 100% for the diagnosis of vascular injury [60]. Catheter angiography may be useful when CTA is inconclusive (eg, possible arteriovenous fistula) or when endovascular intervention is being considered [45]. Head Trauma CT Head Please refer to CTA for neurovascular imaging evaluation of suspected intracranial arterial injury. Concurrent CT may be useful in the clinical setting of suspected intracranial arterial injury for assessing structural changes to the brain since the most recent neuroimaging study (eg, new or progressive neurologic deficit). Concurrent head CT is also useful in the initial imaging evaluation of head trauma when there is no prior imaging. CTA Head and Neck Although catheter angiography is the historical reference standard and offers the highest spatial/temporal resolution for imaging evaluation of vascular pathology, noninvasive CTA is faster, has fewer safety concerns, and is most useful in the initial imaging evaluation of suspected intracranial arterial injury [45].


Head Trauma PCAs

Head Trauma PCAs. With modern CT equipment, accuracy has been shown to be comparable. One prospective study of 146 trauma patients who received both catheter angiography and CTA (16-slice multidetector-row) reported the latter to have a sensitivity of 97.7% and a specificity of 100% for the diagnosis of vascular injury [60]. The development of >8-slice multidetector-row CT has allowed CTA to become the standard in diagnosis of suspected cerebrovascular injury, with reported sensitivities up to 100% (somewhat dependent on both CT technology and radiologist expertise) [57]. There is a Biffl grading scale for arterial injury, which was originally developed for catheter angiography and carotid artery injury but has also been shown to be reliable for CTA and vertebral artery injury [56]. Grade I = dissection with <25% luminal narrowing (intimal irregularity), Grade II = dissection with >25% luminal narrowing (intramural hematoma), Grade III = pseudoaneurysm (contained hematoma), Grade IV = occlusion, and Grade V = transection or hemodynamically significant arteriovenous fistula (eg, carotid cavernous fistula). Medical therapy with antiplatelet or anticoagulation may be appropriate management for the lower grades of arterial injury, whereas the higher grades of arterial injury are more likely to require endovascular or surgical treatment [56,57]. FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the imaging evaluation of suspected intracranial arterial injury. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the imaging evaluation of suspected intracranial arterial injury. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the imaging evaluation of suspected intracranial arterial injury.


Head Trauma PCAs

Head Trauma PCAs. MRA Head and Neck In the setting of acute trauma, MRA is considered a second-line noninvasive option behind CTA, which is faster, has fewer safety concerns, and is most useful in the initial imaging evaluation of suspected intracranial arterial injury [45]. MRA may be useful outside of the acute setting or when CTA is inconclusive (eg, for detection of T1 hyperintense subacute intramural hematoma in traumatic arterial dissection) [57]. Noncontrast MRA, using time- of-flight technique, can be used in patients who cannot receive iodinated or gadolinium-based contrast. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the imaging evaluation of suspected intracranial arterial injury. MRI Head Please refer to MRA for neurovascular imaging evaluation of suspected intracranial arterial injury. Concurrent MRI may be useful in the clinical setting of suspected intracranial arterial injury for assessing structural changes to the brain since the most recent neuroimaging study (eg, new or progressive neurologic deficit). MRI Head with DTI There is no relevant literature to support the use of DTI in the imaging evaluation of suspected intracranial arterial injury. Radiography Skull There is no relevant literature to support the use of radiographs in the imaging evaluation of suspected intracranial arterial injury. Head Trauma Variant 9: Head trauma with suspected intracranial venous injury due to clinical risk factors or positive findings on prior imaging. Traumatic venous injury is an often-overlooked pathology that includes epithelial injury with thrombus formation and venous laceration with compressive hematoma [57]. The most common symptoms are highly variable and nonspecific (eg, headache and papilledema from intracranial hypertension or focal neurologic deficits from venous ischemia); they may be mistakenly attributed to other traumatic injuries [61].


Head Trauma PCAs

Head Trauma PCAs. From an imaging standpoint, the most important risk factor for traumatic venous injury is a skull fracture (or less commonly a penetrating foreign body) that involves a dural venous sinus or jugular bulb/foramen. In a retrospective study of 195 patients with closed head trauma who received multidetector-row CTV, acute traumatic venous sinus thrombosis was seen only in those patients with fractures extending to a dural sinus or jugular bulb (41% rate of thrombosis), and hemorrhagic venous infarctions were seen only in the setting of occlusive dural venous sinus thrombosis (55% of all thromboses) [62]. Another retrospective study of 472 patients with closed head trauma with skull fracture crossing a dural venous sinus also identified a high incidence of small epidural hemorrhages (81%), which can be compressive and misdiagnosed as venous sinus thrombosis [61]. Direct observation of hyperattenuating thrombus within a dural venous sinus on a noncontrast CT should prompt further evaluation; however, this is present in only one-third of venous sinus thrombosis. Indirect evidence of dural sinus thrombosis includes venous infarcts (subcortical edema), one-third of which develop parenchymal hemorrhage [30]. Arteriography Cervicocerebral There is no relevant literature to support the use of catheter angiography in the imaging evaluation of suspected intracranial venous injury. CT Head Please refer to CTV for neurovascular imaging evaluation of suspected intracranial venous injury. Concurrent CT may be useful in the clinical setting of suspected intracranial venous injury for assessing structural changes to the brain since the most recent neuroimaging study (eg, new or progressive neurologic deficit). Concurrent head CT is also useful in the initial imaging evaluation of head trauma when there is no prior imaging. FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the imaging evaluation of suspected intracranial venous injury.


Head Trauma PCAs

Head Trauma PCAs. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the imaging evaluation of suspected intracranial venous injury. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the imaging evaluation of suspected intracranial venous injury. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the imaging evaluation of suspected intracranial venous injury. MRI Head Please refer to MRV for neurovascular imaging evaluation of suspected intracranial venous injury. Concurrent MRI may be useful in the clinical setting of suspected intracranial venous injury for assessing structural changes to the brain since the most recent neuroimaging study (eg, new or progressive neurologic deficit). Head Trauma MRI Head with DTI There is no relevant literature to support the use of DTI in the imaging evaluation of suspected intracranial venous injury. MRV Head In the setting of acute trauma, MRV is considered a second-line noninvasive option behind CTV, which is faster, has fewer safety concerns, and is most useful in the initial imaging evaluation of suspected intracranial venous injury [58]. MRV may be useful outside of the acute setting, and noncontrast MRV using time-of-flight or phase- contrast techniques can be used in patients who cannot receive iodinated or gadolinium-based contrast. Radiography Skull There is no relevant literature to support the use of radiographs in the imaging evaluation of suspected intracranial venous injury. CT Head Cisternography CT cisternography is high-resolution CT (HRCT) of the skull base after a lumbar puncture for intrathecal administration of approximately 10 mL of an iodinated contrast agent (eg, 3 g of iodine).


Head Trauma PCAs

Head Trauma PCAs. Its sensitivity for contrast leakage from the subarachnoid space into the sinonasal or tympanomastoid cavities depends on the rate of CSF leak and ranges between 85% and 92% in patients with an active leak versus 40% in patients with an inactive or intermittent leak [64]. Noninvasive noncontrast HRCT has a high sensitivity of 84% to 95% and has replaced traditional use of minimally invasive contrast-enhanced CT cisternography in the initial imaging evaluation of suspected CSF leak with laboratory confirmation [64,65]. No additional preoperative neuroimaging is necessary when a single skull base defect is identified on the HRCT; when there are multiple potential CSF leak sites, then follow-up CT cisternography is indicated [58,64]. Head Trauma FDG-PET/CT Brain There is no relevant literature to support the use of FDG-PET/CT in the initial imaging evaluation of suspected CSF leak. HMPAO SPECT or SPECT/CT Brain There is no relevant literature to support the use of SPECT in the initial imaging evaluation of suspected CSF leak. MR Spectroscopy Head There is no relevant literature to support the use of MRS in the initial imaging evaluation of suspected CSF leak. MRI Functional (fMRI) Head There is no relevant literature to support the use of fMRI in the initial imaging evaluation of suspected CSF leak. MRI Head MR cisternography is the use of high-resolution T2-weighted or steady-state free precession sequences to look for CSF communication or meningoencephalocele across a defect in the skull base. It is a second-line noninvasive imaging option in the setting of suspected CSF leak with laboratory confirmation that has a reported accuracy of 89% and sensitivity of 87%, which is lower than HRCT [66]. It may be useful as a follow-up study when there is a suspected meningoencephalocele on HRCT (eg, soft-tissue mass with bone erosion) or when preoperative HRCT is unable to pinpoint a single osseous defect in the skull base.


Pretreatment Detection Surveillance and Staging of Prostate Cancer.  Introduction/Background Prostate cancer ranks second only after lung cancer as a leading cause of cancer-related deaths in American patients. In 2020, an estimated 191,930 American patients were diagnosed with prostate cancer, and 33,330 died of the disease [1]. In addition to the personal toll of these deaths, there is a substantial amount of direct economic costs related to prostate cancer in the Unites States at an estimated $10 billion per year [2]. The primary goal during pretreatment evaluation of prostate cancer is disease detection, localization, and characterization, that is, establishing disease extent, both local and distant, and aggressiveness, because these drive patient outcomes in terms of recurrence and survival. Reprint requests to: publications@acr.org Special Imaging Considerations A few emerging imaging techniques have not yet made their way into mainstream clinical practice, showing the potential to improve detection of the primary tumor, nodal, and distant metastatic disease in addition to achieving better risk stratification. Studies on advanced ultrasound (US) techniques have focused on assessment of the primary prostate tumor [31-36]. For example, a recent meta-analysis showed that shear wave elastography had a pooled sensitivity and specificity of 83% and 85%, respectively [31]. In addition, targeted biopsy using real-time elastography was able to improve the Gleason score assignment when added to systematic biopsy than systematic biopsy alone (68.3% versus 56.7%) [32]. High-resolution micro-US has also shown potential to improve detection of clinically significant prostate cancer [33]. Furthermore, when a multiparametric approach was used for US using B-mode, shear wave elastography and contrast-enhanced US, it was able to improve the sensitivity in detecting index lesions compared with B-mode alone (74% versus 55%) [34].


Pretreatment Detection Surveillance and Staging of Prostate Cancer. Regarding assessment of lymph nodes, MR using ultrasmall superparamagnetic iron oxide (USPIO) has shown promise to detect even micrometastatic deposits [37,38]. Two agents, ferumoxtran-10 and ferumoxytol, have been investigated based on their lymphotropic properties, accumulating in normal but not metastatic lymph nodes after injected intravenously. In a prospective multicenter study of intermediate- and high-risk patients with prostate cancer, ferumoxtran-10 showed significantly higher sensitivity (82% versus 34%) than CT with a similar specificity (93% versus 97%) [37]. Moreover, when ferumoxtran-10-based USPIO MRI was performed in conjunction with diffusion-weighted imaging, it yielded impressive results even in normal-sized lymph nodes (sensitivities and specificities of 65%-75% and 93%-96%) [38]. Nevertheless, issues related to iron overload and potential life- threatening allergic reactions have been raised, which need to be addressed before its usage in pretreatment prostate imaging. Pretreatment Detection of Prostate Cancer Choline PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of choline PET/CT for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. Choline PET/MRI Skull Base to Mid-Thigh There is limited evidence to support the use of choline PET/MRI for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. CT Abdomen and Pelvis With IV Contrast There is limited evidence to support the use of CT abdomen and pelvis with intravenous (IV) contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. CT Abdomen and Pelvis Without and With IV Contrast There is limited evidence to support the use of CT abdomen and pelvis without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy.


Pretreatment Detection Surveillance and Staging of Prostate Cancer. CT Abdomen and Pelvis Without IV Contrast There is limited evidence to support the use of CT abdomen and pelvis without IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. CT Chest, Abdomen, and Pelvis With IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis with IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. CT Chest, Abdomen, and Pelvis Without and With IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. CT Chest, Abdomen, and Pelvis Without IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis without IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. FDG-PET/CT Whole Body Because prostate cancer and metastases from it are generally not fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)- avid unlike most other malignancies, FDG-PET/CT may not be beneficial as part of initial imaging. FDG-PET/MRI Skull Base to Mid-Thigh Because prostate cancer and metastases from it are generally not FDG-avid unlike most other malignancies, FDG- PET/MRI may not be beneficial as part of initial imaging. Fluciclovine PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of fluciclovine PET/CT for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. Fluciclovine PET/MRI Skull Base to Mid-Thigh There is limited evidence to support the use of fluciclovine PET/MRI for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy.


Pretreatment Detection Surveillance and Staging of Prostate Cancer. Fluoride PET/CT Whole Body There is limited evidence to support the use of fluoride PET/CT for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. MRI Abdomen and Pelvis Without and With IV Contrast There is limited evidence to support the use of MRI abdomen and pelvis without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. Pretreatment Detection of Prostate Cancer MRI Abdomen and Pelvis Without IV Contrast There is limited evidence to support the use of MRI abdomen and pelvis without IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. MRI Pelvis Without IV Contrast More recently, there has been increase in the performance of MRI pelvis without IV contrast, albeit with controversy regarding the additive benefit of IV gadolinium-based contrast media for assessing prostate cancer. Unlike diffusion-weighted imaging, which is undoubtedly an essential component of prostate MRI, there has been debate over whether dynamic contrast-enhanced imaging should be retained, used but limited to assessing the presence of early and/or contemporaneous enhancement (as in the current PI-RADS schema), or even omitted altogether [50,51]. Despite the notion that detection of prostate cancer could be improved by using dynamic contrast-enhanced imaging, owing to the fact that prostate cancer typically enhances more rapidly and washes out more quickly than benign prostatic tissue, many studies have shown that the incremental diagnostic yield is minimal [52-54]. For instance, in a meta-analysis of 20 studies (2,142 patients) performing a head-to-head comparison of biparametric and multiparametric MRI, sensitivity and specificity were similar: 0.74 (95% CI: 0.66-0.81) and 0.90 (95% CI: 0.86-0.93) for biparametric and 0.76 (95% CI: 0.69-0.82) and 0.89 (95% CI: 0.85-0.93) for multiparametric, respectively [54].


Pretreatment Detection Surveillance and Staging of Prostate Cancer. Omitting dynamic contrast-enhanced imaging additionally offers benefits of decreasing study time. Nevertheless, biparametric MRI is not yet widely adopted, and it is recommended that when performed, several requirements need to be met, such as good image quality (especially diffusion-weighted imaging), potential radiologist monitoring, and a safety net for missing significant cancers (eg, PSA follow-up). MRI Whole Body Without and With IV Contrast There is limited evidence to support the use of MRI whole body without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. MRI Whole Body Without IV Contrast There is limited evidence to support the use of MRI whole body without IV contrast for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. PSMA PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of prostate-specific membrane antigen (PSMA) PET/CT (or PET/MRI) for initial imaging of patients with clinically suspected prostate cancer and no prior biopsy. TRUS Prostate In North America, TRUS is generally performed by urologists for purposes of localizing the prostate gland (not the cancer) prior to systematic biopsy. Conventional grayscale TRUS is not widely used for localizing the tumor, first because lesions (usually hypoechoic in appearance) are visible only in a small proportion (11%-35%) of patients [65]. In a study of 142 patients, grayscale TRUS was able to detect only 62.2% of lesions visible on multiparametric MRI [66]. Second, only a small proportion (17%-57%) of those hypoechoic lesions are confirmed to be malignant [65]. In a study of 31,296 cores obtained from 3,912 consecutive patients undergoing TRUS with biopsy, there was no statistically significant association between the presence of a hypoechoic lesion and the detection of cancer [67].


Pretreatment Detection Surveillance and Staging of Prostate Cancer. Therefore, in isolation, TRUS is inaccurate for prostate cancer detection and is not beneficial for this purpose [65]. Variant 2: Clinically suspected prostate cancer. Negative TRUS-guided biopsy. Initial diagnosis. Next imaging study. Bone Scan Whole Body There is limited evidence to support the use of bone scan as the next imaging study of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. Pretreatment Detection of Prostate Cancer Choline PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of choline PET/CT for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. Choline PET/MRI Skull Base to Mid-Thigh There is limited evidence to support the use of choline PET/MRI for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. CT Abdomen and Pelvis With IV Contrast There is limited evidence to support the use of CT abdomen and pelvis with IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. CT Abdomen and Pelvis Without and With IV Contrast There is limited evidence to support the use of CT abdomen and pelvis without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. CT Abdomen and Pelvis Without IV Contrast There is limited evidence to support the use of CT abdomen and pelvis without IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically.


Pretreatment Detection Surveillance and Staging of Prostate Cancer. CT Chest, Abdomen, and Pelvis With IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis with IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. CT Chest, Abdomen, and Pelvis Without and With IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. CT Chest, Abdomen, and Pelvis Without IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis without IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. FDG-PET/CT Whole Body Because prostate cancer and metastases from it are generally not FDG-avid unlike most other malignancies, FDG- PET/CT may not be beneficial as part of initial imaging. FDG-PET/MRI Skull Base to Mid-Thigh Because prostate cancer and metastases from it are generally not FDG-avid unlike most other malignancies, FDG- PET/MRI may not be beneficial as part of initial imaging. Fluciclovine PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of fluciclovine PET/CT for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. Fluciclovine PET/MRI Skull Base to Mid-Thigh There is limited evidence to support the use of fluciclovine PET/MRI for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically.


Pretreatment Detection Surveillance and Staging of Prostate Cancer. Fluoride PET/CT Whole Body There is limited evidence to support the use of fluoride PET/CT for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. MRI Abdomen and Pelvis Without and With IV Contrast There is limited evidence to support the use of MRI abdomen and pelvis without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. Pretreatment Detection of Prostate Cancer MRI Abdomen and Pelvis Without IV Contrast There is limited evidence to support the use of MRI abdomen and pelvis without IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. MRI Pelvis Without IV Contrast In patients with clinically suspected prostate cancer who had a negative TRUS-guided biopsy, imaging without using IV contrast is also a viable option based on the identical rationales for using MRI of the pelvis with IV contrast [29,40,44,45,49]. Nevertheless, controversies exist with regard to balancing between the small incremental yield for detecting clinically significant cancer using IV contrast and potential benefits such as decreased scan time when forgoing IV contrast [50-54]. MRI Whole Body Without and With IV Contrast There is limited evidence to support the use of MRI whole body without and with IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically.


Pretreatment Detection Surveillance and Staging of Prostate Cancer. MRI Whole Body Without IV Contrast There is limited evidence to support the use of MRI whole body without IV contrast for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. PSMA PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of PSMA PET/CT (or PET/MRI) for initial imaging of patients with clinically suspected prostate cancer unless or until the presence of higher-risk disease has been established histologically. TRUS Prostate In isolation, TRUS is inaccurate for prostate cancer detection and is not useful for this purpose [65,66]. TRUS-Guided Biopsy Prostate In patients with clinically suspected prostate cancer who have had 1 negative standard TRUS-guided systematic biopsy, a second TRUS-guided systematic biopsy will be positive in 15% to 20% of cases [73-76], and so a second repeat biopsy in this setting is reasonable. The yield from additional systematic biopsies after a second biopsy falls off rapidly, with reported positive rates of 8% to 17% for the third biopsy and 7% to 12% for the fourth [73-75,77], suggesting alternative approaches such as MRI-targeted biopsy or saturation biopsy may be more useful in this specific setting of patients with 2 or more negative TRUS-guided systematic biopsies and persistent clinical suspicion for prostate cancer. Choline PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of choline PET/CT for active surveillance of patients with clinically established low-risk prostate cancer. Choline PET/MRI Skull Base to Mid-Thigh There is limited evidence to support the use of choline PET/MRI for active surveillance of patients with clinically established low-risk prostate cancer.


Pretreatment Detection Surveillance and Staging of Prostate Cancer. CT Abdomen and Pelvis With IV Contrast There is limited evidence to support the use of CT abdomen and pelvis with IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. CT Abdomen and Pelvis Without and With IV Contrast There is limited evidence to support the use of CT abdomen and pelvis without and with IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. CT Abdomen and Pelvis Without IV contrast There is limited evidence to support the use of CT abdomen and pelvis without IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. CT Chest, Abdomen, and Pelvis With IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis with IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. CT Chest, Abdomen, and Pelvis Without and With IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis without and with IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. CT Chest, Abdomen, and Pelvis Without IV Contrast There is limited evidence to support the use of CT chest, abdomen, and pelvis without IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. FDG-PET/CT Whole Body Because prostate cancer and metastases from it are generally not FDG-avid unlike most other malignancies, FDG- PET/CT may not be beneficial as part of active surveillance. FDG-PET/MRI Skull Base to Mid-Thigh Because prostate cancer and metastases from it are generally not FDG-avid unlike most other malignancies, FDG- PET/MRI may not be beneficial as part of active surveillance.


Pretreatment Detection Surveillance and Staging of Prostate Cancer. Fluciclovine PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of fluciclovine PET/CT for active surveillance of patients with clinically established low-risk prostate cancer. Fluciclovine PET/MRI Skull Base to Mid-Thigh There is limited evidence to support the use of fluciclovine PET/MRI for active surveillance of patients with clinically established low-risk prostate cancer. Fluoride PET/CT Whole Body There is limited evidence to support the use of fluoride PET/CT for active surveillance of patients with clinically established low-risk prostate cancer. Pretreatment Detection of Prostate Cancer MRI Abdomen and Pelvis Without and With IV Contrast There is limited evidence to support the use of MRI abdomen and pelvis without and with IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. MRI Abdomen and Pelvis Without IV Contrast There is limited evidence to support the use of MRI abdomen and pelvis without IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. MRI Pelvis Without and With IV Contrast There has been a substantial increase in the role of MRI in active surveillance in terms of detecting/predicting disease progression and identifying targets amenable for biopsy. In a meta-analysis of 43 studies (6,605 patients), the sensitivity and negative predictive value of predicting disease reclassification were 0.60 and 0.75 using 1.5T scanners and 0.81 and 0.78 using 3.0T scanners [81]. In addition, several studies have shown that MRI is at least equivalent or superior to systematic TRUS-guided biopsies in identifying pathological progression during follow- up in patients on active surveillance [82-84].


Pretreatment Detection Surveillance and Staging of Prostate Cancer. In a prospective trial of 172 patients who underwent active surveillance, in which at 3 years 21% experienced pathological progression, MRI using PI-RADS was able to identify many of them (a sensitivity of 61% and a specificity of 80%) [82]. In addition, in a study in which 86 patients who had diffusion-weighted imaging as part of their baseline assessment for active surveillance and followed up for a median of 9.5 years, it was able to predict patients with a shorter time to adverse histology (hazard ratio [HR] = 2.13, 95% CI: 1.17-3.89) and a shorter time to radical treatment (HR 2.54, 95% CI: 1.49-4.32; P < . 001) [83]. MRI can also be used in conjunction with nonimaging biomarkers to better identify patients with an increased risk of biopsy upgrading [84]. MRI Pelvis Without IV Contrast Initial imaging without using IV contrast is also a viable option based on the identical rationales for using MRI of the pelvis with IV contrast [81-84]. Especially, there are studies that specifically address the usage of diffusion- weighted imaging (which is typical done without or prior to administration of IV contrast) for baseline assessment on active surveillance, demonstrating that it was helpful for predicting patients with shorter time to adverse histology and radical treatment [83]. MRI Whole Body Without and With IV Contrast There is limited evidence to support the use of MRI whole body without and with IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. MRI Whole Body Without IV Contrast There is limited evidence to support the use of MRI whole body without IV contrast for active surveillance of patients with clinically established low-risk prostate cancer. PSMA PET/CT Skull Base to Mid-Thigh There is limited evidence to support the use of PSMA PET/CT (or PET/MRI) for active surveillance of patients with clinically established low-risk prostate cancer. Pretreatment Detection of Prostate Cancer


Pretreatment Detection Surveillance and Staging of Prostate Cancer. TRUS Prostate In general, TRUS is inaccurate for prostate cancer detection [65,67] and has a limited accuracy for staging prostate cancer [93]. Other than one retrospective study of 875 patients who demonstrated the association between imaging progression on TRUS and biopsy Gleason upgrade [94], there is lack of evidence to support TRUS in evaluating on active surveillance. TRUS-Guided Biopsy Prostate Many active surveillance programs incorporate serial PSA testing and some form of serial biopsy regimen, either in the form of 1) systemic biopsy only or 2) systemic biopsy with MRI-targeted biopsy of a suspicious lesion on MRI. Because some tumors are invisible on MRI [82] and missed by MRI-targeted biopsies [91,92], even when performing an MRI-targeted biopsy as part of active surveillance, concurrent systemic biopsies cannot be omitted at the moment. Choline PET/CT Skull Base to Mid-Thigh Choline PET, although it was approved by the FDA in 2013 for evaluating recurrence, has been widely investigated on its ability to detect nodal and distant metastases for pretreatment assessment of prostate cancer. The pooled sensitivity of choline PET/CT is low (0.57, 95% CI: 0.42-0.70) for detecting nodal metastases prior to treatment despite its high specificity (0.94, 95% CI: 0.89-0.97) in a meta-analysis of 7 studies (627 patients) [98]. Nevertheless, in patients with intermediate- and high-risk prostate cancer, choline PET/CT and PET/MRI has shown to identify more nodal and distant metastatic lesions than conventional imaging [96,98]. For example, in a study of 48 patients, choline PET/CT showed higher sensitivity (46.2% versus 69.2%) with identical specificity (92.3%) for detecting nodal metastases [99]. This in turn has shown to change in management in 33% to 71% of patients [99,100].


Pretreatment Detection Surveillance and Staging of Prostate Cancer. Choline PET/MRI Skull Base to Mid-Thigh Choline PET/MRI is less commonly used than choline PET/CT but can be considered in the pretreatment assessment of prostate cancer based on the same principles that it better detects nodal and distant metastases than CT and bone scan [96,98-100]. For example, in a study of 48 patients with intermediate- and high-risk disease, choline PET/CT showed a higher sensitivity (46.2% versus 69.2%) with identical specificity (92.3%) for detecting nodal metastases [99]. In a prospective study specifically assessing choline PET/MRI in 58 patients, it was superior to CT and bone scan for detecting distant metastases (100% versus 63.6%, respectively) [101]. CT Abdomen and Pelvis With IV Contrast CT abdomen and pelvis with IV contrast for nodal staging is generally useful in intermediate-risk patients because the a priori risk of nodal disease exceeds 10% [20]. CT Abdomen and Pelvis Without and With IV Contrast There is limited evidence to support the use of CT abdomen and pelvis without and with IV contrast because obtaining CT with both techniques does not provide additional benefit in terms of detecting nodal and distant metastases. Pretreatment Detection of Prostate Cancer CT Abdomen and Pelvis Without IV Contrast CT abdomen and pelvis without IV contrast can be a viable option as an alternative for using IV contrast for nodal staging because it is generally useful in intermediate-risk patients because the a priori risk of nodal disease exceeds 10% [20]. However, it should be recognized that without using IV contrast there is possibility of less optimal detection of metastases to visceral organs. CT Chest, Abdomen, and Pelvis With IV Contrast CT chest, abdomen, and pelvis with IV contrast for nodal staging is generally useful in intermediate-risk patients because the a priori risk of nodal disease exceeds 10% [20].