Suspected Lower Extremity Deep Vein Thrombosis. With this technique, proximal compression tourniquets are applied, and a series of overlapping radiographs are obtained following an iodine-containing contrast medium injection into a dorsal vein in the foot. DVT is present if a distinct filling defect is present in a deep vein, typically in the calf or thigh, but it can often extend to or involve more proximal veins, such as those in the pelvis. Less specific findings for DVT include an abrupt contrast cut- off, the absence of contrast filling, or the presence of collateral venous vessels. Although the techniques have evolved to catheter-directed venography using fluoroscopy, the risks and benefits are felt to be the same. MR Venography Lower Extremity and Pelvis MR venography (MRV) is a noninvasive alternative to contrast catheter venography. MRV does have inherent advantages over US, especially in its ability to delineate extravascular anatomy. MRV can help identify potential sources of extrinsic venous compression (ie, May-Thurner syndrome or a mass) that can be an underlying cause for DVT or suggest alternative diagnoses that mimic DVT. Suspected Lower Extremity DVT specificity, 95.2%) comparable to that of US for diagnosing proximal DVT [23]. CTV can also be incorporated into a comprehensive examination that includes pulmonary CT angiography for evaluating both pulmonary embolism and proximal DVT [26], but it should not be performed routinely in all patients who are being evaluated for pulmonary embolism [27]. There is little evidence to support the use of CTV to diagnose DVT; however, based on the published experience with pulmonary embolism, CTV may be considered a reasonable alternative to MRV for pelvic DVT or when US is nondiagnostic. Summary of Recommendations Variant 1: US duplex Doppler lower extremity is the recommended initial imaging examination for patients with suspected lower extremity DVT.


Second and Third Trimester Screening for Fetal Anomaly.  Introduction/Background Major congenital anomalies occur in 3% to 4% and minor anomalies occur in 7% to 10% of the population [1-3]. Anomalies increase the risk of aneuploidy, syndromes, and poor outcome [2]. Congenital anomalies account for 22.1% of infant deaths, with fetal malformations causing increased morbidity and mortality in the neonatal/postnatal period [3]. 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. Reprint requests to: publications@acr.org Second and Third Trimester Screening for Fetal Anomaly Special Imaging Considerations Transvaginal US The transvaginal US scan can be performed to supplement a transabdominal US scan where a fetal body part is close to the cervix and cannot be visualized transabdominally. Transvaginal US at 12 to 16 weeks can improve evaluation of fetal anatomy in obese women [8,10,21,22]. 3-D and 4-D US Both 3-D and 4-D US have been helpful to further evaluate anatomy, especially facial clefts, spine anomalies such as hemivertebra, and midline brain anomalies such as agenesis of the corpus callosum or abnormalities of the posterior fossa [23,24]. In addition, 3-D and 4-D US [25] can be used as an adjunct to fetal echocardiography [26]. CT CT has an extremely limited role to play in evaluation of the fetus, predominantly restricted to some cases of skeletal anomalies [27]. OR Discussion of Procedures by Variant Variant 1: Second and third trimester screening for fetal anomaly. Low-risk pregnancy. Initial imaging. In the developed world, US is usually performed at least once during pregnancy [28].


Second and Third Trimester Screening for Fetal Anomaly. A review of 11 randomized trials and quasi-randomized trials looked at outcomes for US performed routinely versus selective US at <24 weeks. Although perinatal mortality was not affected, there was increased detection of fetal anomalies, improved detection of multiple gestations, and lower rates of induction for postdates. Long-term follow-up of children exposed to US in utero showed no detrimental effects on cognitive or physical development, supporting the safety of US [9]. There are several systematic reviews and large studies, which report fetal anomaly detection rates between 16% and 56% on US performed prior to 24 weeks [5,8,9]. The rate of detection of lethal anomalies is higher, up to 84% [8,29]. MRI Fetal Without and With IV Contrast There is no relevant literature to support the use of fetal MRI with and without intravenous (IV) contrast for screening of a fetal anomaly in a low-risk pregnancy. MRI Fetal Without IV Contrast There is no relevant literature to support the use of fetal MRI without IV contrast for screening of a fetal anomaly in a low-risk pregnancy. US Echocardiography Fetal There is no relevant literature to support the use of fetal echocardiography for screening of a fetal anomaly in a low- risk pregnancy. US Pregnant Uterus Transabdominal Detailed Scan There is no relevant literature to support the use of US pregnant uterus transabdominal detailed scan for screening of a fetal anomaly in a low-risk pregnancy. Second and Third Trimester Screening for Fetal Anomaly US Pregnant Uterus Transabdominal Anatomy Scan The Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a fetal imaging workshop in December 2012, resulting in a multispecialty panel recommending that at least one US be offered routinely to all pregnant women between 18 and 20 weeks of gestation [8].


Second and Third Trimester Screening for Fetal Anomaly. The components of the standard fetal examination at 18 to 20 weeks have been agreed upon by several organizations and outlined in the ACR-ACOG- AIUM-SMFM-SRU Practice Parameter for the Performance of Standard Diagnostic Obstetrical Ultrasound [8,30]. A routine diagnostic US may be used in the third trimester, either selectively or in the setting of a late arrival for assessment. Bricker et al [31] reviewed 13 trials with 34,980 patients and showed no evidence of improved antenatal, obstetric, or neonatal outcome or morbidity in those screened in the third trimester versus controls. A study by Manegold et al [32]; however, showed third trimester US to have utility for perinatal management and postnatal follow-up, with 15% of all anomalies found only in the third trimester in a study of 8,074 fetuses. Variant 2: Second and third trimester screening for fetal anomaly. High-risk pregnancy. Initial imaging. Detailed fetal anatomic examinations are performed in high-risk pregnancy instances where there is increased risk for anatomic or karyotypic fetal abnormality based on maternal factors (including age, use of in vitro fertilization, drug dependence, infection, or other maternal medical conditions) or abnormality of screening testing (including the quad screen, NIPT, or US findings). The category of high risk also includes family history of genetic disease or abnormality, multi-gestational pregnancies, and teen pregnancies [33]. A German study looked at teenage pregnancies in a database of all pregnancies from 2000 to 2011 and found 638 pregnancies in women <20 years of age, with a total of 9.2% of patients having anomalies or aneuploidy [34]. Obese patients deserve special consideration as rates of congenital anomalies are increased, particularly involving neural tube defects, cardiovascular anomalies, cleft lip or palate, anorectal atresia, hydrocephaly, and limb reduction anomalies [35,36].


Second and Third Trimester Screening for Fetal Anomaly. Several studies demonstrate decreased detection of fetal anomalies with increasing body mass index (likely related to suboptimal visualization) on routine and detailed examinations [36-40]. An anatomic survey in obese women should be considered at 20 to 22 weeks (about 2 weeks later than women of normal weight), and if incomplete, a repeat follow-up US should be considered in 2 to 4 weeks [8,40-44]. There is emerging evidence that anatomic studies performed earlier in gestation with transvaginal imaging may be helpful [36-39]. A recent Canadian publication has demonstrated that performing early anatomic evaluation by transvaginal technique in combination with routine transabdominal study at 18 to 22 weeks can result in completion rates of the anatomic study that are comparable to those in nonobese populations [21]. This method should especially be considered in completion of the anatomic study in the high-risk obese population. MRI Fetal Without and With IV Contrast MRI abdomen and pelvis with IV contrast is not recommended for fetal evaluation. There are no documented fetal indications for the use of MRI contrast, but there may be rare instances where contrast is potentially helpful in evaluating maternal anatomy or pathology, to be decided on a case by case basis [45]. MRI Fetal Without IV Contrast The International Society of Ultrasound in Obstetrics and Gynecology current guidelines recommend that fetal MRI is generally indicated following an US examination in which the information about the abnormality is incomplete. Although MRI is usually reserved for patients with a known or suspected anomaly, MRI can be helpful in screening fetuses with a family risk for brain abnormalities, as well as for assessment of fetal brain development [8,45-47]. If performed, this is ideally done at or after 22 weeks gestation [8], although an MRI performed between 18 to 22 weeks may be of value in certain clinical indications and settings [48].


Second and Third Trimester Screening for Fetal Anomaly. US Echocardiography Fetal The decision for the performance of fetal echocardiography, a subspecialized examination, is based on parental and fetal risk factors, as well as abnormal fetal cardiac screening examination. These risk factors include maternal genetic disease or risk, current medical conditions, and chemical exposures, as well as fetal factors such as known or suspected anomaly or cardiac abnormality [49-51]. US Pregnant Uterus Transabdominal Detailed Scan High-risk patients should have a detailed scan, which is an indication-driven examination performed for a known or suspected fetal anatomic abnormality, known fetal growth disorder, genetic abnormality, or increased risk for a fetal anatomic or genetic abnormality [33,52]. Second and Third Trimester Screening for Fetal Anomaly US Pregnant Uterus Transabdominal Anatomy Scan There is no relevant literature to support the use of US pregnant uterus transabdominal anatomy scan for the second and third trimester screening for fetal anomaly in high-risk patients [33]. However, if the chorionic villous sampling, amniocentesis, or NIPT are normal, then the risk is diminished and a routine scan could be performed [8]. Variant 3: Second and third trimester screening for abnormal finding on ultrasound: soft markers. Next imaging study. Soft markers are minor sonographic findings that have little or no pathologic significance, but may be associated with aneuploidy, most commonly trisomies 21 and 18, and other syndromes or pathologies. Soft markers have been used to recalculate the age-related trisomy risk and decrease the need for invasive testing when identified on the anatomy US examination [8,53,54]. MRI Fetal Without and With IV Contrast There is no relevant literature to support the use of fetal MRI with and without IV contrast in the evaluation of fetuses with soft markers.


Second and Third Trimester Screening for Fetal Anomaly. MRI Fetal Without IV Contrast There is no relevant literature to support the use of fetal MRI without IV contrast in the evaluation of fetuses with soft markers. US Pregnant Uterus Transabdominal Follow-up If one or more required structures are not adequately demonstrated during the detailed fetal anatomic examination, if the study is considered incomplete, or if there is reason for follow-up of an anomaly identified on the screening or detailed examination, the patient may be brought back for a focused follow-up assessment [33]. Even if the fetus is euploid, follow-up US is recommended at 32 weeks for the following soft markers: pyelectasis, short humerus length, short femur length, and echogenic bowel [8,17,59,62,63]. US Pregnant Uterus Transabdominal Detailed Scan If a soft marker is found on the anatomy scan, a detailed US examination can be performed at the same time to look for additional markers and anomalies, or may be scheduled for the near future. For soft markers that relate only to aneuploidy risk, such as echogenic intracardiac focus and choroid plexus cyst, a detailed scan is optional to be certain the finding is isolated. For other soft markers, such as renal pyelectasis, short humerus and femur, nuchal thickening, echogenic bowel, and short or absent nasal bone, a detailed scan is usually indicated [8,17,52,59,61]. Second and Third Trimester Screening for Fetal Anomaly MRI Fetal Without and With IV Contrast MRI abdomen and pelvis with IV contrast is not recommended for fetal evaluation. There are no documented fetal indications for the use of MRI contrast, but there may be rare instances where contrast is potentially helpful in evaluating maternal anatomy or pathology, to be decided on a case by case basis [45].


Second and Third Trimester Screening for Fetal Anomaly. MRI Fetal Without IV Contrast The International Society of Ultrasound in Obstetrics and Gynecology current guidelines recommend that fetal MRI is generally indicated following an US examination in which the information about the abnormality is incomplete [48]. Under these circumstances, MRI may provide important information that may confirm or complement the US findings and alter or modify patient management [79,84-88]. Fetal MRI is especially helpful for central nervous system anomalies, planning for prenatal and postnatal intervention, and for airway management in fetuses with neck masses [4,8,11]. Other indications for fetal MRI include evaluation of cranial, facial, thoracic, abdominal, retroperitoneal, and pelvic anomalies, as well as complications of monochorionic gestations [89]. Although available data are still inconclusive, MRI for parental reassurance regarding the absence of associated pathologies in fetuses with apparently isolated conditions may be recommended in fetuses with the following sonographic findings: isolated ventriculomegaly, agenesis of the corpus callosum, absent cavum septi pellucidi, and cerebellar or vermian anomalies [48]. If fetal MRI is performed, this is ideally done at or after 22 weeks gestation [8], although an MRI performed between 18 to 22 weeks may be of value in certain clinical indications and settings [48]. US Echocardiography Fetal The decision for the performance of fetal echocardiography, a subspecialized examination, is based on parental and fetal risk factors, as well as abnormal fetal cardiac screening examination. These risk factors include maternal genetic disease or risk, current medical conditions, and chemical exposures, as well as fetal factors such as known anomaly or cardiac abnormality [49-51].


Imaging of Suspected Intracranial Hypotension PCAs.  Introduction/Background The clinical syndrome of intracranial hypotension refers to the symptoms caused by cerebrospinal fluid (CSF) hypovolemia and is primarily characterized by postural headaches [1,2]. According to the International Classification of Headache Disorders, third edition, the low CSF pressure headache is typically orthostatic in nature, is caused by low CSF pressure (<6 cm H2O) or CSF leakage, and remits after normalization of CSF pressure or a successful sealing of the CSF leak [3]. The onset of symptoms may be spontaneous or secondary depending on a temporal relation to a presumed cause, such as a recent procedural dural puncture. Headache symptoms may be accompanied by additional symptomatology to include nausea, vomiting, neck pain, tinnitus, changes in hearing, and photophobia [4]. It is estimated that spontaneous intracranial hypotension (SIH) occurs with an incidence of approximately 5 per 100,000 individuals annually [5]. The true incidence of this condition may be higher, because SIH is thought to be both highly underdiagnosed and a misdiagnosed disorder [4,6-8]. Clinical risk factors for the development of SIH include spinal osteophytes that can perforate the dura, weakened ectatic dura/meningeal cysts as can be seen with collagen vascular disease, and a history of bariatric surgery in which it is postulated that rapid loss of epidural fat may weaken the dura and predispose to CSF leakage [4,9-12]. Secondary intracranial hypotension symptoms related to dural puncture are thought to occur with a frequency of approximately 2% to 8% of cases, with risk factors in part related to needle type and gauge used [13-15].


Imaging of Suspected Intracranial Hypotension PCAs. The pathophysiologic mechanism of headache symptoms and various neurological deficits in patients with intracranial hypotension is not well understood but likely multifactorial and may be attributed to 1) compensatory venodilitation, blood volume expansion, and dural sinus stretching as the body attempts to maintain a stable intracranial volume in response to decreased CSF volume; and 2) downward traction on the meninges, nerves, and brain parenchyma as the brain loses buoyancy and begins to sag in response to decreased CSF volume. The findings of venodilitation and brain sagging have well-defined imaging findings and have been shown to resolve along with clinical improvement of headache symptoms [16,17]. The 3 main causes of intracranial hypotension are CSF leakage through a dural defect, leaking meningeal diverticulum, and CSF-venous fistula [18-20]. It is important to note that in the upright position, intracranial hydrostatic pressure is slightly negative relative to atmosphere, whereas hydrostatic pressure in the spine is positive relative to atmosphere [21]. Consequently, the spine has been shown to represent the anatomical source of most symptomatic CSF leaks and venous fistulas, such that the imaging investigation of leak source should be directed primarily toward the spine and not intracranially [22]. Imaging plays a critical role in the diagnostic evaluation of intracranial hypotension. The goals of imaging are 2- fold: 1) to confirm the diagnosis of intracranial hypotension and 2) to localize the source of leak for targeted therapy such as epidural blood patch, percutaneous fibrin glue treatment, endovascular venous fistula embolization, and surgical dural repair or venous fistula ligation [23,24]. Intracranial imaging features suggestive of intracranial aMayo Clinic Arizona, Phoenix, Arizona. bPanel Chair, Mallinckrodt Institute of Radiology, Saint Louis, Missouri. cThe Ohio State University Wexner Medical Center, Columbus, Ohio.


Imaging of Suspected Intracranial Hypotension PCAs. dMontefiore Medical Center, Bronx, New York. eWashington University School of Medicine, Saint Louis, Missouri. fEmory University School of Medicine, Atlanta, Georgia; American Association of Neurological Surgeons/Congress of Neurological Surgeons. gHospital of the University of Pennsylvania, Philadelphia, Pennsylvania. hUniversity of Utah Health, Salt Lake City, Utah. iUniversity of Rochester Medical Center, Rochester, New York; American Academy of Neurology. jThomas Jefferson University Hospital, Philadelphia, Pennsylvania. kJacobi Medical Center, Bronx, New York. lBrigham & Women's Hospital, Boston, Massachusetts; Committee on Emergency Radiology-GSER. mUniversity of California San Francisco, San Francisco, California. nSchmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida; American College of Emergency Physicians. oUniversity of Cincinnati, Cincinnati, Ohio; Commission on Nuclear Medicine and Molecular Imaging. pSpecialty Chair, University of Iowa Hospitals and Clinics, Iowa City, Iowa. 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. Reprint requests to: publications@acr.org Imaging of Suspected Intracranial Hypotension hypotension include qualitative signs (engorgement of venous sinuses, pachymeningeal enhancement, midbrain descent, superficial siderosis, subdural hygroma or hematoma, and convex superior surface of the pituitary) and quantitative signs (pituitary height, pontomesencephalic angle, suprasellar cistern, prepontine cistern, midbrain descent, venous-hinge angle, mamillopontine angle, tonsillar descent, and area cavum veli interpositi) [4,16,25-27].


Imaging of Suspected Intracranial Hypotension PCAs. The cumulative presence of these intracranial findings has been shown to correlate with a likelihood of finding a spinal leak source [16]. The spinal imaging findings associated with SIH include direct evidence of CSF leakage via epidural fluid collections and CSF-venous fistula as well as secondary indirect signs of CSF leakage such as dilated epidural venous plexus, subdural hygromas, and dural enhancement [24,28-30]. It should be noted that CSF pressure can be normal in patients with SIH, and the absence of a low CSF pressure should not exclude this condition [31,32]. It also bears mentioning that the diagnosis of SIH is challenging, and in some cases SIH cannot be definitely diagnosed or excluded until a full diagnostic workup with invasive imaging (myelography) has been performed. In cases in which symptoms persist after a negative full imaging workup, the possibility of SIH mimicking pathologies such as positional orthostatic tachycardia syndrome, cervicogenic headaches, migraines, or new daily persistent headache syndromes should be considered [33]. Using the best available evidence, this document provides diagnostic imaging recommendations for intracranial hypotension across various clinical presentations. In cases in which conservative/medical management or a therapeutic procedural intervention may be a more appropriate first step over imaging, the evidence to support such practices is discussed in the variant narrative. OR Discussion of Procedures by Variant Variant 1: Adult. Orthostatic headache from suspected intracranial hypotension, without recent spinal intervention that could cause CSF leakage. Initial imaging. This clinical scenario refers to a patient who demonstrates postural orthostatic headaches with or without additional secondary SIH symptoms.


Imaging of Suspected Intracranial Hypotension PCAs. The absence of a recent spinal intervention such as a dural puncture is relevant because orthostatic headaches are known, usually self-limiting sequelae of such procedures that do not typically require an imaging workup [4,13]. Orthostatic headaches without a temporal relation to dural puncture usually require 2 initial imaging examinations: brain imaging to help confirm a suspected SIH diagnosis and spine imaging to assist in localizing a potential source of CSF leak [4]. CT Complete Spine With IV Contrast There is no relevant literature to support the use of CT complete spine with intravenous (IV) contrast in the initial imaging of suspected SIH. CT Complete Spine Without and With IV Contrast There is no relevant literature to support the use of CT complete spine without and with IV contrast in the initial imaging of suspected SIH. CT Complete Spine Without IV Contrast There is no relevant literature to support the use of CT complete spine without IV contrast in the initial imaging of suspected SIH. CT Head Cisternography There is no relevant literature to support the use of CT head cisternography in the initial imaging of suspected SIH. The spine has been shown to represent the anatomical source of most symptomatic CSF leaks and venous fistulas, Imaging of Suspected Intracranial Hypotension such that the imaging investigation of leak source should be directed primarily toward the spine and not intracranially [22]. CT Head With IV Contrast There is no relevant literature to support the use of CT head with IV contrast in the initial imaging of suspected SIH. CT Head Without and With IV Contrast There is no relevant literature to support the use of CT head without and with IV contrast in the initial imaging of suspected SIH. CT Head Without IV Contrast There is no relevant literature to support the use of CT head without IV contrast in the initial imaging of suspected SIH.


Imaging of Suspected Intracranial Hypotension PCAs. CT Myelography Complete Spine Although CT myelography complete spine can detect epidural contrast collections suggestive of dural defect or leaking meningeal diverticulum, MRI complete spine optimized with fluid sensitive sequences has been shown to detect epidural collections with equal sensitivity and is a preferred initial imaging option over CT myelography complete spine because it avoids the need for lumbar puncture [34-36]. CT Myelography Dynamic Complete Spine There is no relevant literature to support the use of dynamic CT myelography complete spine in the initial imaging of suspected SIH. Dynamic CT myelography plays an important role in the subsequent imaging workup of SIH after the initial brain and spine imaging [37,38]. Results from an initial spine MRI or conventional CT myelogram provide useful information on how a subsequent dynamic CT myelogram will be performed, such as prone positioning for suspected ventral dural defect or decubitus positioning for suspected leaking meningeal diverticulum or CSF-venous fistula [24,37-39]. Dynamic CT myelography involves an initial scan followed by delayed phase scans in immediate succession and, when performed in the decubitus position, may require 2 separate contrast injections due to the transient temporal characteristics associated with CSF-venous fistula visualization as well as limitations in contrast dosing [40-44]. DTPA Cisternography Although diethylenetriamine pentaacetate (DTPA) cisternography can detect epidural collections suggestive of dural defect or leaking meningeal diverticulum, MRI complete spine optimized with fluid sensitive sequences is typically the preferred initial imaging option over DTPA cisternography complete spine because it avoids the need for lumbar puncture and has superior spatial resolution for lesion localization [45,46]. MR Myelography Complete Spine There is no relevant literature to support the use of MR myelography complete spine in the initial imaging of suspected SIH.


Imaging of Suspected Intracranial Hypotension PCAs. An MR myelogram with intrathecal gadolinium administration has been used in several studies as a subsequent follow-up imaging examination after initial spine imaging to increase sensitivity for the detection of slow leaking dural and meningeal diverticular defects [47-49]. Some limited evidence suggests a potential role for MR myelography in the detection of CSF-venous fistulas [50]. It should be noted that intrathecal use of gadolinium is currently off label. Although studies have suggested that intrathecal gadolinium can be administered safely in small doses, the safety profile of such imaging is not formally approved for such use, and special dosing caution is required to avoid potential of gadolinium induced neurotoxicity [51]. MRI Complete Spine With IV Contrast There is no relevant literature to support the use of MRI complete spine with IV contrast in the initial imaging of suspected SIH. MRI Complete Spine Without and With IV Contrast MRI complete spine without and with IV contrast can be useful in the initial evaluation of suspected SIH. The noncontrast component of this examination optimized with fluid sensitive sequences is most useful, particularly when performed with 3-D T2-weighted fat saturated sequences, which increases sensitivity for detecting fluid collections outside of the thecal sac [52]. It can detect with a high degree of accuracy the presence of epidural fluid collections and meningeal diverticula that can inform positioning and regions of interest for subsequent CSF leak localization imaging examinations, such as dynamic CT myelogram complete spine and digital subtraction myelography complete spine [25,34-36]. The contrast component of this examination may demonstrate dural Imaging of Suspected Intracranial Hypotension enhancement and engorged epidural venous plexus, which are also imaging features that support a diagnosis of SIH [28,29].


Imaging of Suspected Intracranial Hypotension PCAs. MRI Complete Spine Without IV Contrast MRI complete spine without IV contrast optimized with fluid sensitive sequences is most useful in the initial evaluation of suspected SIH, particularly when performed with 3-D T2-weighted fat saturated sequences, which increases sensitivity for detecting fluid collections outside of the thecal sac [52]. This examination can detect with a high degree of accuracy the presence of epidural fluid collections and meningeal diverticula that can inform positioning and regions of interest for subsequent CSF leak localization imaging examinations, such as dynamic CT myelogram complete spine and digital subtraction myelography complete spine [25,34-36]. MRI Head With IV Contrast There is no relevant literature to support the use of MRI head with IV contrast in the initial imaging of suspected SIH. MRI Head Without and With IV Contrast MRI head without and with IV contrast is most useful in the initial evaluation of suspected SIH. Suggestive imaging features of SIH are best visualized on MRI head without and with IV contrast and include qualitative signs (engorgement of venous sinuses, pachymeningeal enhancement, midbrain descent, superficial siderosis, subdural hygroma or hematoma, and convex superior surface of the pituitary) and quantitative signs (pituitary height, pontomesencephalic angle, suprasellar cistern, prepontine cistern, midbrain descent, venous-hinge angle, mamillopontine angle, tonsillar descent, and area cavum veli interpositi) [16,25,26]. The cumulative presence of these intracranial findings has been shown to correlate with the likelihood of finding a spinal leak source [16]. MRI Head Without IV Contrast MRI head without IV contrast can be useful in the initial evaluation of suspected SIH.


Imaging of Suspected Intracranial Hypotension PCAs. Although imaging features of suspected SIH are best visualized on MRI head without and with IV contrast, some imaging features such as midbrain descent, superficial siderosis, subdural hygroma or hematoma, convex superior surface of the pituitary, pituitary height, pontomesencephalic angle, suprasellar cistern, prepontine cistern, midbrain descent, venous-hinge angle, mamillopontine angle, tonsillar descent, and area cavum veli interpositi may be evaluated on noncontrast MRI sequences [16,25,26]. The cumulative presence of these intracranial findings has been shown to correlate with likelihood of finding a spinal leak source [16]. Radiographic Myelography Digital Subtraction Complete Spine There is no relevant literature to support the use of dynamic digital subtraction myelography in the initial imaging of suspected SIH. Dynamic digital subtraction myelography plays an important role in the subsequent imaging workup of SIH after initial brain and spine imaging [53]. Results from an initial spine MRI or conventional CT myelogram provide useful information on how a subsequent dynamic digital subtraction myelogram will be performed, such as prone positioning for suspected ventral dural defect or decubitus positioning for suspected leaking meningeal diverticulum or CSF-venous fistula [24,53,54]. Dynamic digital subtraction myelography involves continuous real-time fluoroscopic x-ray imaging of the entire spine or of a focused region of the spine where there is suspicion for CSF leak. When performed in the decubitus position, 2 separate contrast injections may be required due to the transient temporal characteristics associated with CSF-venous fistula visualization as well as limitations in contrast dosing [40-44]. Variant 2: Adult. Orthostatic headache from suspected intracranial hypotension within 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. Initial imaging.


Imaging of Suspected Intracranial Hypotension PCAs. Leakage of CSF following a dural puncture may be of sufficient volume to elicit symptoms of intracranial hypotension. Postdural puncture headaches occur with an estimated frequency of 2% to 8% [13-15]. Risk factors for postdural puncture headaches include the use of a larger gauge needle, multiple attempts at dural puncture, the use of a cutting needle versus pencil point tip needle, needle orientation perpendicular rather than parallel to spine longitudinal axis (when using a cutting needle), and dural puncture in the sitting position as opposed to lateral decubitus positioning [55-58]. Imaging is not typically indicated in this clinical setting because postdural puncture headaches are typically self-limited, with most symptoms fully resolving within 1 week without any treatment [13]. The initial management of postdural puncture headaches is conservative medical management, with consideration of epidural blood patch if symptoms are severe or not beginning to resolve by 2 to 3 days postdural puncture [59- 61]. Imaging of Suspected Intracranial Hypotension CT Complete Spine With IV Contrast There is no relevant literature to support the use of CT complete spine with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. CT Complete Spine Without and With IV Contrast There is no relevant literature to support the use of CT complete spine without and with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. CT Complete Spine Without IV Contrast There is no relevant literature to support the use of CT complete spine without IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. CT Head Cisternography There is no relevant literature to support the use of CT head cisternography in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture.


Imaging of Suspected Intracranial Hypotension PCAs. CT Head With IV Contrast There is no relevant literature to support the use of CT head with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. CT Head Without and With IV Contrast There is no relevant literature to support the use of CT head without and with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. CT Head Without IV Contrast There is no relevant literature to support the use of CT head without IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. CT Myelography Complete Spine There is no relevant literature to support the use of CT myelography complete spine in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. CT Myelography Dynamic Complete Spine There is no relevant literature to support the use of dynamic CT myelography complete spine in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. DTPA Cisternography There is no relevant literature to support the use of DTPA cisternography in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. MR Myelography Complete Spine There is no relevant literature to support the use of MR myelography complete spine in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. MRI Complete Spine With IV Contrast There is no relevant literature to support the use of MRI complete spine with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. MRI Complete Spine Without and With IV Contrast There is no relevant literature to support the use of MRI complete spine without and with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture.


Imaging of Suspected Intracranial Hypotension PCAs. MRI Complete Spine Without IV Contrast There is no relevant literature to support the use of MRI complete spine without IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. MRI Head With IV Contrast There is no relevant literature to support the use of MRI head with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. MRI Head Without and With IV Contrast There is no relevant literature to support the use of MRI head without and with IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. Imaging of Suspected Intracranial Hypotension MRI Head Without IV Contrast There is no relevant literature to support the use of MRI head without IV contrast in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. Radiographic Myelography Digital Subtraction Complete Spine There is no relevant literature to support the use of dynamic digital subtraction myelography complete spine in the initial imaging of suspected intracranial hypotension within 72 hours of dural puncture. Variant 3: Adult. Orthostatic headache from suspected intracranial hypotension without improvement post 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. Initial imaging. This clinical variant refers to a patient with orthostatic headache in temporal relation to a dural puncture that is not improving following a trial of conservative management. Imaging is not usually warranted in this clinical scenario, because the next management step for such patients typically involves an epidural blood patch procedure directed at the level of dural puncture [59-61].


Imaging of Suspected Intracranial Hypotension PCAs. CT Complete Spine With IV Contrast There is no relevant literature to support the use of CT complete spine with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. CT Complete Spine Without and With IV Contrast There is no relevant literature to support the use of CT complete spine without and with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. CT Complete Spine Without IV Contrast There is no relevant literature to support the use of CT complete spine without IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. CT Head Cisternography There is no relevant literature to support the use of CT head cisternography in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. CT Head With IV Contrast There is no relevant literature to support the use of CT head with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. CT Head Without and With IV Contrast There is no relevant literature to support the use of CT head without and with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage.


Imaging of Suspected Intracranial Hypotension PCAs. CT Head Without IV Contrast There is no relevant literature to support the use of CT head without IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. CT Myelography Complete Spine There is no relevant literature to support the use of CT myelography complete spine in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. CT Myelography Dynamic Complete Spine There is no relevant literature to support the use of dynamic CT myelography complete spine in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. Imaging of Suspected Intracranial Hypotension DTPA Cisternography There is no relevant literature to support the use of DTPA cisternography in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. MR Myelography complete spine There is no relevant literature to support the use of MR myelography complete spine in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. MRI Complete Spine With IV Contrast There is no relevant literature to support the use of MRI complete spine with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage.


Imaging of Suspected Intracranial Hypotension PCAs. MRI Complete Spine Without and With IV Contrast There is no relevant literature to support the use of MRI complete spine without and with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. MRI Complete Spine Without IV Contrast There is no relevant literature to support the use of MRI complete spine without IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. MRI Head With IV Contrast There is no relevant literature to support the use of MRI head with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. MRI Head Without and With IV Contrast There is no relevant literature to support the use of MRI head without and with IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. MRI Head Without IV Contrast There is no relevant literature to support the use of MRI head without IV contrast in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. Radiographic Myelography Digital Subtraction Complete Spine There is no relevant literature to support the use of dynamic digital subtraction myelography complete spine in the initial imaging of suspected intracranial hypotension without improvement after 72 hours of dural puncture or other spinal intervention that could cause CSF leakage. Variant 4: Adult. Obtundation with initial brain imaging features of suspected intracranial hypotension. Next imaging study.


Imaging of Suspected Intracranial Hypotension PCAs. This clinical scenario represents a severe clinical manifestation of SIH, which may represent sequela of more severe mechanical traction forces from brain sagging in the setting of CSF hypovolemia [62,63]. There are some limited reports of successful acute management of these critically ill patients with intrathecal saline infusions via lumbar drains, which may serve as a temporizing measure to raise CSF pressure and reverse obtundation [64-67]. The subsequent management of such patients is otherwise similar to patients with SIH without impaired consciousness and focuses on spine imaging to localize a source of leak that may be targeted for definitive treatment [24]. CT Complete Spine With IV Contrast There is no relevant literature to support CT complete spine with IV contrast as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. Imaging of Suspected Intracranial Hypotension CT Complete Spine Without and With IV Contrast There is no relevant literature to support CT complete spine without and with IV contrast as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. CT Complete Spine Without IV Contrast There is no relevant literature to support CT complete spine without IV contrast as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. CT Myelography Complete Spine Although CT myelography complete spine can detect epidural contrast collections suggestive of dural defect or leaking meningeal diverticulum, MRI complete spine optimized with fluid sensitive sequences has been shown to detect epidural collections with equal sensitivity and is a preferred initial imaging option over CT myelography complete spine because it avoids the need for lumbar puncture [34,35].


Imaging of Suspected Intracranial Hypotension PCAs. CT Myelography Dynamic Complete Spine There is no relevant literature to support the use of dynamic CT myelography complete spine as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. Dynamic CT myelography plays an important role in the subsequent imaging workup of SIH after initial brain and spine imaging [37,38]. Results from an initial spine MRI or conventional CT myelogram provide useful information on how a subsequent dynamic CT myelogram will be performed, such as prone positioning for suspected ventral dural defect or decubitus positioning for suspected leaking meningeal diverticulum or CSF-venous fistula [24,37- 39]. Dynamic CT myelography involves an initial scan followed by delayed phase scans in immediate succession and, when performed in the decubitus position, may require 2 separate contrast injections due to the transient temporal characteristics associated with CSF-venous fistula visualization as well as limitations in contrast dosing [40-44]. DTPA Cisternography Although DTPA cisternography can detect epidural collections suggestive of dural defect or leaking meningeal diverticulum, MRI complete spine optimized with fluid sensitive sequences is typically the preferred initial imaging option over DTPA cisternography complete spine because it avoids the need for lumbar puncture and has superior spatial resolution for lesion localization [45,46]. MR Myelography Complete Spine There is no relevant literature to support the use of MR myelography complete spine as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. An MR myelogram with intrathecal gadolinium administration has been used in several studies as a subsequent follow-up imaging examination after initial spine imaging to increase the sensitivity for detection of slow leaking dural and meningeal diverticular defects [47-49].


Imaging of Suspected Intracranial Hypotension PCAs. Some limited evidence suggests a potential role for MR myelography in the detection of CSF-venous fistulas [50]. It should be noted that intrathecal use of gadolinium is currently off label. Although studies have suggested that intrathecal gadolinium can be administered safely in small doses, the safety profile of such imaging is not formally approved for such use, and special dosing caution is required to avoid potential of gadolinium induced neurotoxicity [51]. MRI Complete Spine With IV Contrast There is no relevant literature to support the use of MRI complete spine with IV contrast as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. MRI Complete Spine Without and With IV Contrast MRI complete spine without and with IV contrast can be useful as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. The noncontrast component of this examination optimized with fluid sensitive sequences is most useful, particularly when performed with 3-D T2-weighted fat saturated sequences, which increases the sensitivity for detecting fluid collections outside of the thecal sac [52]. It can detect with a high degree of accuracy the presence of epidural fluid collections and meningeal diverticula that can inform positioning and regions of interest for subsequent CSF leak localization imaging examinations, such as dynamic CT myelogram complete spine and digital subtraction myelography complete spine [25,34-36]. The contrast component of this examination may demonstrate dural enhancement and engorged epidural venous plexus, which are also imaging features that support a diagnosis of SIH [28,29].


Imaging of Suspected Intracranial Hypotension PCAs. Imaging of Suspected Intracranial Hypotension MRI Complete Spine Without IV Contrast MRI complete spine without IV contrast optimized with fluid sensitive sequences is most useful as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension, particularly when performed with 3-D T2-weighted fat saturated sequences, which increases sensitivity for detecting fluid collections outside of the thecal sac [52]. This examination can detect with a high degree of accuracy the presence of epidural fluid collections and meningeal diverticula that can inform positioning and regions of interest for subsequent CSF leak localization imaging examinations, such as dynamic CT myelogram complete spine and digital subtraction myelography complete spine [25,34-36]. Radiographic Myelography Digital Subtraction Complete Spine There is no relevant literature to support the use of dynamic digital subtraction myelogram complete spine as a next imaging study in the clinical setting of obtundation with initial brain imaging features of suspected intracranial hypotension. Dynamic digital subtraction myelography plays an important role in the subsequent imaging workup of SIH after initial brain and spine imaging [53]. Results from an initial spine MRI or conventional CT myelogram provide useful information on how a subsequent dynamic digital subtraction myelogram will be performed, such as prone positioning for suspected ventral dural defect or decubitus positioning for suspected leaking meningeal diverticulum or CSF-venous fistula [24,53,54]. Dynamic digital subtraction myelography involves continuous real- time fluoroscopic x-ray imaging of the entire spine or of a focused region of the spine where there is suspicion for CSF leak.


Imaging of Suspected Intracranial Hypotension PCAs. When performed in the decubitus position, 2 separate contrast injections may be required due to the transient temporal characteristics associated with CSF-venous fistula visualization as well as limitations in contrast dosing [40-44]. Variant 5: Adult. Chronic daily headache from suspected intracranial hypotension with negative initial brain and spine imaging, but with history and clinical examination suggesting CSF leakage. Next imaging study. Negative initial imaging should not preclude continued diagnostic workup in a patient with clinically suspected SIH [4,53]. Approximately 20% of initial brain MRIs and 46% to 67% of initial spine imaging in patients with clinically suspected SIH may have normal results [4]. Of note, CSF-venous fistulas and slow meningeal diverticular leaks are often subtle imaging findings that may not be readily detectable using conventional imaging techniques with limited temporal resolution and may require follow-up imaging with more advanced imaging procedures to definitely identify or exclude a more subtle spinal CSF leak source [7,53,68-70]. CT Head Cisternography There is no relevant literature to support the use of CT head cisternography in the subsequent imaging of suspected SIH. The spine has been shown to represent the anatomical source of most symptomatic CSF leaks and venous fistulas, such that the imaging investigation of leak source should be directed primarily toward the spine and not intracranially [22]. CT Myelography Dynamic Complete Spine Dynamic CT myelography plays an important role in the subsequent imaging workup of SIH after initial brain and spine imaging [37,38]. Results from an initial spine MRI or conventional CT myelogram provide useful information on how a subsequent dynamic CT myelogram will be performed, such as prone positioning for suspected ventral dural defect or decubitus positioning for suspected leaking meningeal diverticulum or CSF-venous fistula [24,37- 39].


Imaging of Suspected Intracranial Hypotension PCAs. Dynamic CT myelography involves an initial scan followed by delayed phase scans in immediate succession and, when performed in the decubitus position, may require 2 separate contrast injections due to the transient temporal characteristics associated with CSF-venous fistula visualization as well as limitations in contrast dosing [40-44]. DTPA Cisternography DTPA cisternography of the spine can detect CSF leaks with similar accuracy to conventional CT myelography [45]. Due to its limited spatial resolution, a positive DTPA cisternogram may require further investigation with subsequent dynamic CT myelography or dynamic digital subtraction myelography to definitively localize leak for treatment planning [45,46]. MR Myelography Complete Spine An MR myelogram with intrathecal gadolinium administration has been used in several studies to increase sensitivity for the detection of slow leaking dural and meningeal diverticular defects [47-49]. Some limited evidence suggests a potential role for MR myelography in the detection of CSF-venous fistulas [50]. It should be noted that intrathecal use of gadolinium is currently off label. Although studies have suggested that intrathecal gadolinium can Imaging of Suspected Intracranial Hypotension be administered safely in small doses, the safety profile of such imaging is not formally approved for such use, and special dosing caution is required to avoid potential of gadolinium induced neurotoxicity [51]. Radiographic Myelography Digital Subtraction Complete Spine Dynamic digital subtraction myelography plays an important role in the subsequent imaging workup of SIH after initial brain and spine imaging [53].


Penetrating Neck Injury PCAs

Penetrating Neck Injury PCAs.  Current approaches to patients with penetrating neck injuries result from clinical evaluation and the findings of hard versus soft signs. Hard signs of vascular or aerodigestive injury include active hemorrhage, pulsatile or expanding hematoma, bruit or thrill in the region of the wound, hemodynamic instability, unilateral upper- extremity pulse deficit, massive hemoptysis or hematemesis, air bubbling in the wound, and airway compromise. These hard signs of injury are associated with an unstable or a potentially unstable patient and often mandate immediate operative evaluation and treatment without preoperative imaging. Symptoms related to cerebral ischemia are also hard signs of penetrating injury, but these patients may be stable enough to benefit from first performing imaging studies. Imaging of the brain in addition to the head and neck vasculature may be used to determine optimal surgical, endovascular, or medical therapy. Soft signs of vascular and aerodigestive injury include nonpulsatile or nonexpanding hematoma, venous oozing, dysphagia, dysphonia, and subcutaneous emphysema [6,7]. These commonly result in further evaluation, typically with imaging. Overview of Imaging Modalities CTA dominates the imaging landscape when it comes to the initial evaluation of patients with penetrating neck trauma who do not require immediate surgical exploration [2,6,8,11]. In early comparisons with catheter angiography, CTA demonstrated high sensitivity and specificity [5,11-16]. This held true in a prospective study in 2012 [5] for detecting vascular and aerodigestive injury by CTA, where sensitivity was 100% and specificity was 97.5%. Early adoption of CTA in the initial evaluation of patients with penetrating injuries to the neck led to a The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels.


Penetrating Neck Injury PCAs

Penetrating Neck Injury PCAs. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. *The views expressed in this manuscript are those of the author and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or United States Government. Reprint requests to: publications@acr.org Penetrating Neck Injury decrease in overall neck explorations and negative neck explorations as well as the use of catheter angiography and esophagography [17]. A recent retrospective study [18] reviewed the selective nonoperative management of patients with clinical hard signs. Of patients with hard signs who were hemodynamically stable and had a stable airway, 74% who received a CTA were able to avoid surgical neck exploration. In patients for whom the risk of allergic reaction to iodinated contrast is high or unknown, premedication may be appropriate per ACR recommendations [19]. If there is a high risk for contrast reaction or if iodinated contrast cannot be given, unenhanced computed tomography (CT) imaging of the neck may be performed, but with the understanding the vasculature may be underevaluated. Ultrasound (US) is limited in its use in patients with penetrating neck injury, given the effect of overlying or adjacent soft-tissue injury. It may be complicated by a cervical collar or overlying skin dressings, provides limited evaluation of surrounding structures, and is of limited use in zone I and III injuries [4,13,14,22,23]. Early studies comparing US and catheter-based angiography demonstrated a sensitivity of 91%, a specificity of 98% to 100%, a positive predictive value of 100%, and a negative predictive value of 99% for patients with clinical soft signs imaged by US [24,25]. Fluoroscopic upper gastrointestinal tract examination has its role in the evaluation of penetrating neck injuries but is typically used as a problem-solving modality [2,6,8].


Penetrating Neck Injury PCAs

Penetrating Neck Injury PCAs. Barium swallow, preferably with water-soluble contrast, may miss significant oropharyngeal and hypopharyngeal injuries, although this imaging examination will typically detect esophageal injuries [27]. As arterial injury occurs in a proportion of patients with penetrating neck injury, one must be cognizant of the possibility of end-organ injury, particularly to the brain. Although not directly related to imaging of the neck in penetrating injuries, imaging of the brain and cerebral vasculature may be considered where cervical vascular injury is determined either by clinical examination, imaging, or surgery. Discussion of Procedures by Variant Variant 1: Penetrating neck injury. Clinical soft injury signs. Radiography Radiographs are ubiquitous in radiology and in some practices may be employed in the initial evaluation of acute trauma patients [28]. In the initial evaluation in the trauma bay, radiographs of the neck may demonstrate radio- opaque foreign bodies, soft-tissue swelling, airway competency, fractures, and subcutaneous emphysema. With the exception of patients exhibiting clear hard signs necessitating immediate surgical intervention, the initial radiographs are generally followed by a more detailed CT or CTA evaluation. CTA After the clinical determination is made regarding the need for immediate surgical exploration (eg, presence of hard versus soft signs), CTA is considered the first-line imaging evaluation, replacing catheter angiography as the preferred modality. Multiple studies have shown CTA to have high sensitivity, in the range of 90% to 100%; specificity ranging from 98.6% to 100%; a positive predictive value of 92.8% to 100%; and a negative predictive value of 98% to 100% [5,12,14] for evaluating vascular injury. In addition to identifying vascular injury, CTA simultaneously identifies extravascular soft-tissue and aerodigestive injuries with a sensitivity of 100% and a specificity ranging from 93.5% to 97.5% [2,5,6,8,12-14,17,29].


Penetrating Neck Injury PCAs

Penetrating Neck Injury PCAs. CT esophagography has been described for diagnosing suspected upper-digestive-tract injuries in the trauma setting. There are limited data on this imaging modality, which can be performed either in conjunction with the Penetrating Neck Injury Arteriography, MRI, MRA, US, and Esophagram Although catheter angiography, MRI, MRA, US, and fluoroscopic studies could be used in the initial evaluation of penetrating neck injury, these are typically relegated to problem solving for specific issues in contemporary trauma workups. Variant 2: Penetrating neck injury. Normal or equivocal CTA. Concern for vascular injury. Arteriography Catheter angiography was traditionally used in the evaluation of zones I and III but now is considered primarily in the evaluation of patients with a normal or equivocal CTA with a concerning penetrating foreign body trajectory [6,8] or when endovascular therapy is to be performed [1]. Catheter angiography may be performed in follow-up to equivocal CTA examinations, especially when a clinically significant vascular injury cannot be reliably excluded. A limitation of CTA is the potential for streak artifact from retained metallic foreign bodies; in this instance, digital subtraction catheter angiography may be more sensitive and appropriate for vascular evaluation [20,21]. US Studies in the 1990s demonstrated a high sensitivity and specificity, as well as positive and negative predictive values, of US in patients with penetrating injuries to the neck [24,25,31]. In considering the strengths of US evaluation versus the limitations as discussed, in only very specific circumstances may US provide additional diagnostic insight. For overall structural and functional assessment in the initial evaluation period, arteriography remains the preferred modality.


Penetrating Neck Injury PCAs

Penetrating Neck Injury PCAs. MRA MRA may be feasible in the clinically stable patient for the evaluation of vascular injuries, although limitations such as potential retained foreign bodies and length of the examination may preclude its use [4,13,15,23]. In select and appropriate patients, MRI techniques, including 2-D and 3-D time-of-flight, contrast-enhanced time-resolved, and phase-contrast techniques, are available to evaluate the neck vasculature [32]. The 2-D and 3-D time-of-flight techniques do not require contrast for their technique. Variant 3: Penetrating neck injury. Normal or equivocal CTA. Concern for aerodigestive injury. Barium Swallow Various algorithms are present in practice for the use of esophagrams in the evaluation of aerodigestive injury in the patient with penetrating neck injury. These algorithms vary depending on factors such as whether or not the patient is symptomatic, the degree of clinical concern, the outcome of the initial CT or CTA, and the mechanism of injury [2,6,8,11]. Ahmed et al [27] argue that contrast fluoroscopic studies should not be used in the evaluation of oropharyngeal and hypopharyngeal injuries given that water-soluble and thin barium examinations missed 13 of 13 injuries in this area, compared with video endoscopy performed at the bedside. Water-soluble contrast is preferred, because there is the risk of extraluminal contrast extravasation. Panendoscopy with laryngoscopy, bronchoscopy, and esophagoscopy (flexible and rigid) is the gold standard to rule out oropharyngeal, hypopharyngeal, laryngotracheal, and esophageal injuries. MRI Overall, CT or CTA is preferred when evaluating for acute osseous and soft-tissue cervical injuries. MRI, in particular fat-suppressed T2-weighted imaging, is more sensitive for assessing potential cartilaginous and fibrous injuries but is relegated to specific problem-solving cases and is not routinely performed [26].


Imaging of the Axilla

Imaging of the Axilla.  Introduction/Background Unilateral or bilateral palpable or clinically suspicious axillary mass(es) have a broad differential diagnosis, including inflammatory, infectious, vascular, and malignant etiologies [1]. In most cases, an axillary mass confirmed on imaging is either normal tissue or of lymphoid or mammary origin. With the increased use of ultrasound (US) as a screening tool and as more advanced cross-sectional imaging detects incidental nonpalpable and clinically occult axillary findings, further evaluation with biopsy is often necessary to obtain a definitive diagnosis. The clinically negative axilla is defined having no palpable nodes on physical examination [6]. If the clinical physical examination or imaging test(s) reveal a suspicious finding, then further investigation may involve US and breast MRI. If positive, percutaneous biopsy is often performed. The National Comprehensive Cancer Network (NCCN) guidelines do refer to the use of axillary US or MRI with possible biopsy to determine if there is ipsilateral axillary lymph node involvement in operable breast cancer patients prior to preoperative systemic therapy [7]. Several imaging modalities (mammography, tomosynthesis, US, CT, fluorine-18-2-fluoro-2-deoxy-D-glucose [FDG]-PET/CT, MRI) can visualize the axillary nodes and evaluate the size and morphology. In 2014, the American Society of Breast Surgeons published a consensus guideline on the management of the axilla in which SLNB has replaced ALND for clinically node-negative invasive breast cancer patients [6]. It is desirable to identify those patients who can safely receive SLNB and those who we can potentially omit SLNB. However, there is no standard radiologic imaging test for this purpose. aThe University of Texas MD Anderson Cancer Center, Houston, Texas. bPanel Chair, Boston University School of Medicine, Boston, Massachusetts. cPanel Vice-Chair, New York University School of Medicine, New York, New York.


Imaging of the Axilla

Imaging of the Axilla. dStanford University Medical Center, Stanford, California; Society of Surgical Oncology. eAlpert Medical School of Brown University, Providence, Rhode Island. fSmilow Cancer Hospital, Yale Cancer Center, New Haven, Connecticut; American College of Surgeons. gUniversity of California San Francisco, San Francisco, California. hSutter Medical Group and Sutter Cancer Center, Roseville, California. iUT Southwestern Medical Center, Dallas, Texas; American Society of Clinical Oncology. jEmory University Hospital, Atlanta, Georgia. kBoston Medical Center, Boston, Massachusetts, Primary care physician. lSanford Health of Northern Minnesota, Bemidji, Minnesota. mUniversity of Washington, Seattle, Washington. nMayo Clinic, Phoenix, Arizona. oPerelman School of Medicine of the University of Pennsylvania, Philadelphia, Pennsylvania. pSpecialty Chair, NYU Clinical Cancer Center, New York, New York. 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. Reprint requests to: publications@acr.org Imaging of the Axilla Special Imaging Considerations There are a few publications reporting on the utilization of elastography, contrast-enhanced US, photoacoustic imaging, and MRI with magnetic nanoparticles [16-18]. These advanced imaging methods are still investigational and not recommended for routine clinical use. CT Chest, Abdomen, and Pelvis If a chest wall lesion or an axillary mass invading the chest wall is suspected, CT chest can determine if there is any adjacent bony involvement or any chest wall or pleural space involvement [23]. An axillary mass may also be an incidental imaging finding detected on a CT examination that includes the chest.


Imaging of the Axilla

Imaging of the Axilla. In such situations, further investigation with axillary US and possible US-guided biopsy may be helpful. Digital Breast Tomosynthesis Diagnostic There is insufficient data to support the use of DBT as the single initial imaging test for an axillary palpable mass, even though a portion or all of the axillary mass may be visible on DBT. If there is a personal history of breast cancer or clinical suspicion of axillary tail breast carcinoma, DBT, as an adjunct test to axillary US, can provide a global assessment of the ipsilateral breast and also assess for other suspicious findings such as microcalcifications associated with the palpable axillary mass. DBT allows better characterization of lesions and addresses some of the limitations associated with standard 2-D mammography [24-27]. Imaging of the Axilla If the unilateral axillary mass is suspicious for metastatic adenopathy from a primary breast cancer or occult breast cancer, the reported data from multicenter trials for DBT use in this population, in addition to digital mammography, was associated with an increased primary breast cancer detection rate compared with digital mammogram alone [28]. DBT, in addition to digital mammography, demonstrated best performance gains in women ages 40 to 49 years [29]. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT is not beneficial for assessing an axillary mass of unknown etiology as the initial imaging assessment because of its low yield to detect an occult primary malignancy without first confirming that the unilateral axillary mass is of malignant etiology [30,31]. Less than 1% of breast cancers initially present as axillary adenopathy [32,33]. If FDG-PET/CT incidentally detects an FDG-avid lymph node, then axillary US is helpful to characterize the nodal morphology and guide biopsy, if warranted.


Imaging of the Axilla

Imaging of the Axilla. Mammography Diagnostic There is insufficient data to support the use of mammography as the initial imaging test for an axillary palpable mass, even though pathologically enlarged nodes may be seen as dense enlarged nodes or masses on the mediolateral or mediolateral-oblique projection of a mammogram. However, if there is a personal history of breast cancer or clinical suspicion of axillary tail breast carcinoma or metastatic adenopathy from a breast primary, then mammography as an adjunct test to axillary US can provide global assessment of the ipsilateral breast and identify other suspicious findings such as microcalcifications associated with the palpable mass. MRI Breast MRI of the breast is not routinely performed as the initial imaging assessment for a unilateral palpable axillary mass. MRI may be helpful in defining disease extent and characterizing the breast primary if axillary US reveals adenopathy of unknown primary malignancy and the mammogram is negative for a primary breast malignancy [34,35]. MRI can also help characterize the axillary mass by determining any adjacent vascular involvement, chest wall involvement, and involvement of other axillary structures. Sestamibi MBI There is no relevant literature to support the use of Tc-99m sestamibi molecular breast imaging (MBI) for assessing a unilateral palpable axillary mass. US Axilla Multiple studies support the use of US to characterize findings in the axilla [36,37]. The most common etiology, besides normal tissue, is adenopathy from benign or malignant disease, typically of lymphatic or mammary origin. In addition, accessory breast tissue and both benign and cancerous lesions within accessory tissue can be seen [36]. If a suspicious US finding or mass is identified, US-guided biopsy can be performed for definitive diagnosis, even if the malignancy rate may be low in a woman with palpable axillary mass and no other signs of malignancy [37].


Imaging of the Axilla

Imaging of the Axilla. CT Chest, Abdomen, and Pelvis There is no relevant literature to support the use of CT with or without intravenous (IV) contrast as an initial imaging test for palpable axillary mass. If systemic disease or nonmammary malignancy, such as lymphoma, is in the differential diagnosis, CT chest may be helpful to determine other areas of lymphadenopathy, as well as to assess for local bony, chest wall, or intrathoracic involvement. Digital Breast Tomosynthesis Diagnostic There is insufficient data to support the use of DBT as the initial imaging test for evaluating bilateral palpable axillary masses even though a portion of the axillary region can be visualized on DBT. DBT can provide global assessment of the breasts as well as assess for microcalcifications associated with the axillary mass(es). NCCN guidelines suggest that a diagnostic mammogram and/or DBT may complement axillary US by evaluating the breast for underlying lesions in the setting of patients presenting with axillary lymphadenopathy [7,21,32]. Imaging of the Axilla FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT as the initial imaging test for bilateral axillary adenopathy even though FDG-PET/CT can detect the axillary lymphadenopathy as well as other lymphadenopathy in the neck, chest, abdomen, and pelvis. In one series of breast cancer patients, FDG-PET/CT was significantly more accurate than US (75% versus 62%) for the detection of axillary lymph node metastases, but there was no difference in sensitivity (54% versus 38%) [38]. Incidental axillary FDG uptake on PET/CT may require further evaluation with mammography, DBT, and US, followed by possible image-guided biopsy. MRI Breast MRI of the breast is not routinely performed as the initial imaging assessment for bilateral palpable axillary masses. If digital mammography or DBT is negative for a primary breast malignancy in a patient with suspicious axillary lymphadenopathy, MRI can often identify the breast primary [34,35].


Imaging of the Axilla

Imaging of the Axilla. In a meta-analysis of 9 retrospective studies, MRI detected an occult breast cancer in more than two-thirds of patients [39]. MRI can also help further characterize the axillary mass(es) by determining involvement of adjacent vessels, the chest wall, and other axillary structures. Sestamibi MBI There is no relevant literature to support the use of Tc-99m sestamibi MBI as the initial imaging of patients presenting with bilateral palpable axillary masses. Variant 3: Female. Newly diagnosed breast cancer, 2 cm or less, with clinical node-negative. Initial imaging of the axilla following diagnostic mammography or DBT. Regional nodal staging is an important prognostic factor in guiding the treatment of breast cancer, which has undergone significant change over the last decade [42,43]. Historically, ALND was the standard of care for staging the nodal region and providing local control of breast cancer that has metastasized to regional nodes. The result of the Z0011 trial changed the approach to axillary disease management [5]. The Z0011 trial recruited 891 women with T1 or T2 invasive primary breast cancer and no palpable axillary adenopathy [5]. These women were randomized to SLNB versus ALND. The 10-year overall survival for Z0011 patients treated with SLNB alone was noninferior to those treated with ALND [4]. Therefore, SLNB became a safe alternative to ALND for clinically node-negative breast cancer patients, with a less invasive approach and less morbidity. In 2014, the American Society of Breast Surgeons published consensus guideline on the management of the axilla in which SLNB has replaced ALND for clinically node-negative invasive breast cancer patients [6]. It is desirable to identify those patients who can safely receive SLNB and those who we can potentially omit SLNB. However, there is no standard radiologic imaging test for this purpose and this remains an area of controversy.


Imaging of the Axilla

Imaging of the Axilla. CT Chest, Abdomen, and Pelvis Studies have shown that the use of advanced imaging modalities such as CT and FDG-PET/CT for staging asymptomatic women with early stage breast cancer has low yield for occult disease [44-46]. The 2020 NCCN Guidelines for Invasive Breast Cancer also suggest the use of CT with IV contrast only when there is elevated liver function tests, pulmonary or abdominal symptoms, or abnormal physical examination [7]. CT chest can visualize and assess the level I, II, and III regions of the axilla. The predictive accuracy of CT is not high enough to replace Imaging of the Axilla Sestamibi MBI There is no relevant literature to support the use of Tc-99m sestamibi MBI for staging of the axilla in breast cancer patients. US Axilla Axillary US is often performed in early-stage breast cancer patients since the Z0011 trial showed that early-stage cancer and low nodal burden minimizes surgical morbidity because patients can undergo SLNB rather than ALND without compromising survival [5]. The other point of view supporting preoperative axillary US argues that the finding of an abnormal axillary node on axillary US followed by percutaneous biopsy confirmation would help to identify those patients with higher tumor burden [54,55], who would benefit from proceeding directly to ALND. This approach avoids the need for a Imaging of the Axilla second surgery. One study supporting the utilization of preoperative axillary US from a single center reported that only 3% to 5% of patients had an abnormal axillary US yet met the Z0011 criteria (ie, ALND was not necessary in these patients with preoperative abnormal axillary US). Other studies also supporting the use of preoperative axillary US even in patients who meet Z0011 criteria argue that axillary US can help identify patients with unsuspected extensive nodal disease, thereby removing them from consideration for unindicated SLNB [56-58].


Imaging of the Axilla

Imaging of the Axilla. Patients with negative preoperative axillary US and SLNB had fewer positive nodes, smaller nodal metastases, and lower extranodal extension on final pathology [58]. US-guided biopsy of any suspicious axillary node either via fine-needle aspiration (FNA) or core biopsy is commonly performed when preoperative axillary US is done. The sensitivity of US-guided biopsy is variable with a wide range of 52% to 90%, whereas the specificity is higher, ranging from 98% to 100% [59-63]. CT Chest, Abdomen, and Pelvis Even in women with clinical node-positive disease, contrast-enhanced CT is not routinely performed and is not a part of the initial staging assessment if the patient does not have any signs or symptoms of disease outside the breast. When adenopathy is seen on CT, the Hounsfield unit of the metastatic lymph node is likely higher than nonmetastatic nodes. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT is a valuable modality with potential to impact clinical management of patients with newly diagnosed locally advanced disease, monitoring treatment response in patients with known metastatic breast cancer, and for detection of recurrent disease. FDG-PET/CT is not suggested for routine systemic staging in T0 to T3, N0 to 1, M0 breast cancer patients without signs or symptoms of metastatic disease. A meta-analysis of 25 studies demonstrates the inferiority of FDG-PET/CT to SLNB for evaluation of the axilla [49]. MRI Breast Dynamic contrast-enhanced MRI is useful for staging prior to systemic therapy and for restaging of the axilla after systemic therapy if the preoperative axillary staging was positive [7,48]. However, most of the data focuses on the tumor within the breast and not the axillary nodes.


Imaging of the Axilla

Imaging of the Axilla. Current standard MRI of the breast has some technical challenges that do not allow simultaneous optimal imaging of both the breast and axilla, with approximately 30% of the MRI examination excluding the axilla because of technical challenges or incomplete axillary visualization in a retrospective study of 803 newly diagnosed breast cancer patients [79]. When comparing contrast-enhanced breast MRI with noncontrast breast MRI, contrast-enhanced breast MRI is more accurate than noncontrast MRI, based on Imaging of the Axilla a summary of 6 studies evaluating the accuracy of MRI in detecting pathologically proven positive axillary nodes [52]. In a meta-analysis of 21 eligible studies evaluating the efficacy of MRI versus FDG-PET/CT, the pooled sensitivity of MRI was significantly better (82% versus 64%, respectively), and the pooled specificity of MRI was similar (93%) [69]. A negative MRI does not exclude metastatic nodal disease on final histopathology, but a positive MRI finding suggests high tumor burden (>3 abnormal nodes) [15,69,79]. Based on the review of the literature, there was disagreement for the role of breast MRI in this clinical scenario. Diffusion-weighted imaging (DWI) is a noninvasive imaging technique that does not require contrast injection, measuring the mobility of water molecules and may complement contrast-enhanced MRI. In a meta-analysis of 13 studies from a literature search of 159 articles, the apparent diffusion coefficient value of metastatic nodes are lower than nonmetastatic nodes with pooled sensitivity of 86% and specificity of 86% using a b-value of 800 [80]. Sestamibi MBI There is no relevant literature supporting the routine use of Tc-99m sestamibi MBI for staging of the axilla in breast cancer patients. US Axilla US is the most established noninvasive imaging test for assessing the axilla.


Imaging of the Axilla

Imaging of the Axilla. Benign lymph nodes can often be differentiated from malignant nodes based on size, morphology, and vascularity, although there is a wide range of reported sensitivity and specificity for axillary US. The reported sensitivity can range from 26.4% to 94% and specificity from 53% to 98% [58,81,82]. Axillary US alone has a relatively low NPV and sensitivity to be useful as a predictor of axillary nodal burden [83,84]. When combined with needle biopsy, however, the sensitivity improves from 61% to 79% in a meta-analysis of 21 studies [54,62,85]. US-guided core needle biopsy was superior to US- guided FNA in a meta-analysis of 1,353 patients with newly diagnosed invasive breast carcinoma, with a reported sensitivity of 88% for core biopsy and 74% for FNA [86]. US features associated with a higher likelihood of malignancy include short-axis lymph node size >1 cm, cortical thickness of >0.3cm, and absence of a fatty hilum [87-90]. However, these imaging features are not specific enough to avoid the need for histologic sampling. Since the Z0011 trial, there continues to be variability in incorporating axillary US into practice. Those in favor of performing axillary US routinely argue that >3 abnormal nodes or a positive axillary lymph node on needle biopsy warrant ALND rather than SLNB because these patients tend to have a high nodal tumor burden [58,91]. Those not in favor of performing axillary US recommend proceeding with SLNB, even if the preoperative US identify malignant-appearing lymph node(s) because the specificity of US is relatively low. Variant 5: Female. Newly diagnosed breast cancer, greater than 2 cm, with clinical node-negative. Initial imaging of the axilla following diagnostic mammography or DBT. Lymph node staging is crucial in the management of breast cancer, and several multicenter trials have impacted the approach to axillary lymph node treatment in breast cancer patients.


Imaging of the Axilla

Imaging of the Axilla. For patients with clinically node-negative disease, SLNB is an oncologically safe approach with less morbidity than ALND. The prospective IBCSG 23-01 trial of 934 patients randomized to completion of ALND (n = 465) or no ALND (n = 469), with median follow-up of 9.7 years, revealed that omitting ALND was safe, even if the sentinel nodes contained micrometastases [64]. The NSABP B-32 trial of 5,611 women randomized to SLNB alone versus axillary lymph node biopsy and ALND with follow-up of 8 years reported no statistical differences in overall survival, disease-free survival, and regional control with less postoperative morbidity in the SLNB alone group [2,3]. The Z0011 trial recruited 891 women with T1 or T2 invasive primary breast cancer and no palpable axillary adenopathy [5]. These women were randomized to SLNB versus ALND. The 10-year overall survival for patients treated with SLNB alone was noninferior to those treated with ALND. The Z0011 trial, with median follow-up of 9.3 years, also demonstrated no differences in survival between those who received ALND versus no ALND [5]. The After Mapping of the Axilla: Radiotherapy Or Surgery trial from the European Organization for Research and Treatment of Cancer with median follow-up of 10 years also showed no significant differences at 10 years for axillary recurrence or overall survival between the 2 groups [66]. CT Chest, Abdomen, and Pelvis Contrast-enhanced and noncontrast-enhanced CT studies are not typically performed for early-stage breast cancer in asymptomatic patients because asymptomatic distant disease is rare. Contrast-enhanced CT can be used if the primary breast cancer is >2 cm, there is clinical node-positive disease, the tumor demonstrates biologically Imaging of the Axilla aggressive features on histopathology, or patients present with clinical symptoms such as elevated liver function tests [7,92].


Imaging of the Axilla

Imaging of the Axilla. However, findings on CT do not influence the approach for axillary surgery, reduce the number of axillary surgeries, or reduce the reoperation rate [14,47]. MRI Breast Dynamic contrast-enhanced MRI is not routinely performed [7,92] for staging prior to systemic therapy and for restaging of the axilla after systemic therapy if preoperative axillary staging was negative [7,48]. Current breast MRI protocols do not adequately image the breast and entire axilla in up to 30% of cases based on a retrospective study of 803 newly diagnosed breast cancer patients [79]. However, contrast-enhanced breast MRI is more accurate than noncontrast imaging with a FNR of 12% to 19% and NPV of 97% to 99% based on 6 studies designed to evaluate the accuracy of MRI in patients with histologically positive nodes [52]. In a meta-analysis of 21 eligible studies evaluating the efficacy of MRI versus FDG-PET/CT, the pooled sensitivity of MRI was significantly better (82% versus 64%, respectively), and the pooled specificity was similar (93%) [69]. A negative MRI does not exclude metastatic nodal disease on final histopathology, but a positive MRI finding suggests high tumor burden (>3 abnormal nodes) [15,69,79]. DWI is a noninvasive imaging technique that does not require contrast injection, measures the mobility of water molecules, and may complement contrast-enhanced MRI. In a meta-analysis of 13 studies from a literature search of 159 articles, the apparent diffusion coefficient value of metastatic nodes is lower than nonmetastatic nodes with pooled sensitivity of 86% and specificity of 86% using a b-value of 800 [80]. Sestamibi MBI There is no relevant literature supporting the routine use of sestamibi MBI for staging of the axilla in breast cancer patients.


Imaging of the Axilla

Imaging of the Axilla. The other point of view supporting preoperative axillary US argues that the finding of an abnormal axillary node on axillary US followed by percutaneous biopsy confirmation would help to identify those patients with higher tumor burden [54,55], and these patients would benefit from proceeding directly to ALND. This approach avoids the need for a second surgery. One study, supporting the utilization of preoperative axillary US from a single center, reported that only 3% to 5% of patients had an abnormal axillary US and met the Z0011 criteria (ie, ALND was not necessary in these patients with preoperative abnormal axillary US). Other studies also supporting the addition of preoperative axillary US to the management of patients who met Z0011 criteria argue that axillary US can help identify patients with more extensive nodal disease who meet the Z0011 criteria [56-58]. Patients with negative preoperative axillary US and SLN had fewer positive nodes, smaller nodal metastases, and lower extranodal extension on final pathology [58]. Imaging of the Axilla US-guided biopsy of any suspicious axillary node either via FNA or core biopsy is commonly performed when preoperative axillary US is done. The sensitivity of US-guided biopsy is variable with a wide range of 52% to 90%, whereas the specificity is higher, ranging from 98% to 100% [59-63]. CT Chest, Abdomen, and Pelvis Contrast-enhanced CT is not routinely used to stage the axilla, even in patients with clinically positive axillary findings. While CT chest can visualize and assess the level I, II, and III regions of the axilla, the predictive accuracy of CT is not high enough to replace SLNB [50,51,95]. When adenopathy is seen on CT, the Hounsfield unit of the metastatic lymph node is likely higher than nonmetastatic nodes.


Imaging of the Axilla

Imaging of the Axilla. Contrast-enhanced CT may be used if the primary breast cancer is >2 cm, there is clinical node-positive disease, the tumor demonstrates biologically aggressive features on histopathology, or patients present with clinical symptoms such as elevated liver function tests [7,92]. However, findings on CT do not influence the approach for axillary surgery, reduce the number of axillary surgeries, or reduce the reoperation rate [14,47]. For locally advanced breast cancer (>5 cm in size, involving skin or underlying chest wall) and local recurrence, CT may be helpful [7]. For inflammatory breast cancer, the incidence of nodal metastases at presentation is high, up to 79.8% in a SEER registry of 761 patients and 5-year survival is worse for lymph node-positive patients (49%) than node-negative patients (66%) [98]. If there is clinical suspicion of inflammatory breast cancer, contrast-enhanced CT may be helpful for staging [7]. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT may be useful in the staging of newly diagnosed advanced breast cancer given a higher likelihood of extra-axillary metastatic disease or distant disease [94,95]. It has been proposed that if a primary breast tumor is >2 cm and has a high SUVmax, there is a higher probability of axillary nodal metastases [73,99]. In addition to assisting in the staging of advanced breast cancer, FDG-PET/CT may be beneficial in staging patients with T1 stage breast cancer, particularly those with triple negative or human epidermal growth factor receptor 2 (HER2) positive breast cancer with clinical node positive disease because there is a higher prevalence of nodal disease and distant metastases [71]. In order to assess response to neoadjuvant therapy, comparing pretreatment nodal FDG uptake to subsequent midtreatment or post-treatment FDG uptake is essential and also can be used to identify those at a higher risk of recurrence [100-102].


Imaging of the Axilla

Imaging of the Axilla. MRI Breast Dynamic contrast-enhanced MRI may be useful for staging prior to systemic therapy and for restaging of the axilla after systemic therapy if the preoperative axillary staging was positive [7,48]. However, most of the data focuses on the tumor within the breast and not of the axillary nodes. Current breast MRI protocols do not adequately image the entire axilla (level I, II, III) in up to 30% of cases based on a retrospective study of 803 newly diagnosed breast cancer patients [79]. However, contrast-enhanced breast MRI is more accurate than noncontrast imaging with a FNR of 12% to 19% and NPV of 97% to 99% based on 6 studies designed to evaluate the accuracy of MRI in patients with histologically positive nodes [52]. In a meta-analysis of 21 eligible studies evaluating the efficacy of MRI versus FDG-PET/CT, the pooled sensitivity of MRI was significantly better (82% versus 64%, respectively), and the pooled specificity of MRI was similar (93%) [69]. A negative MRI does not exclude metastatic nodal disease on final histopathology, but a positive MRI finding suggests high tumor burden (>3 abnormal nodes) [15,69,79]. DWI is a noninvasive imaging technique that does not require contrast injection, measures the mobility of water molecules, and may complement contrast-enhanced MRI. In a meta-analysis of 13 studies from a literature search of 159 articles, apparent diffusion coefficient value of metastatic nodes are lower than nonmetastatic nodes with Imaging of the Axilla pooled sensitivity of 86% and specificity of 86% using a b-value of 800 [80]. There is insufficient data to support the use of DWI for detecting metastatic disease in axillary nodes at this time. In summary, although current breast MRI protocols do not consistently image the entire axilla in patients with newly diagnosed breast cancer over 2 cm in size and clinical node-positive, breast MRI can be beneficial for evaluation of tumor within the breast and may be helpful for the axilla in some circumstances.


Imaging of the Axilla

Imaging of the Axilla. Sestamibi MBI There is no relevant literature supporting the use of Tc-99m sestamibi MBI for staging of the axilla in clinically node-positive breast cancer patients. US Axilla Axillary US is typically performed for assessing nodal disease in patients with newly diagnosed breast carcinoma and palpable adenopathy [7,92]. In a retrospective series of 1,287 breast cancer patients who had preoperative axillary US-FNA followed by SLNB or ALND, the group with axillary US-FNA had a higher number of metastatic axillary lymph nodes than those with micro- or macrometastatic nodal disease on SLNB. This suggests that patients with US visible nodal disease, confirmed by axillary US-FNA, have more extensive nodal involvement [60]. Positive axillary US, confirmed with biopsy, helps to identify patients with higher tumor burden [54,55], and as such, these patients can proceed directly to ALND. However, axillary US is not able to detect all metastatic nodes and therefore cannot replace SLNB or ALND [58]. It is well known that negative axillary US with or without biopsy does not rule out nodal disease [58]. The sensitivity of US-guided biopsy also has variable sensitivity ranging from 52% to 90%, whereas the specificity is higher, ranging from 98% to 100% [59-63]. For many cases, axillary US can differentiate patients with high lymph node tumor burden from patients with low lymph node tumor burden, suggesting that those with positive axillary nodes on percutaneous biopsy should have ALND rather than SLNB, especially because the Z0011 criteria do not apply to patients with clinically palpable adenopathy. Axillary US features favoring nodal metastases include cortical thickness of >0.3 cm and absence of a fatty hilum, a finding with a high positive predictive value (PPV) of 90% to 93% [103-105]. CT Chest, Abdomen, and Pelvis CT allows assessment of the axillary level II and III nodal regions that are not always well visualized on US.


Imaging of the Axilla

Imaging of the Axilla. However, there are no data to support the routine use of CT for assessing a new palpable axillary lump in breast cancer patients at midtreatment of NAC and very limited data on the use of CT for assessing nodal response. One retrospective study reviewed the pretreatment breast MRI, FDG-PET/CT, and CT imaging on 348 breast cancer patients who received NAC followed by surgery and reported that patients with higher radiological nodal stage on imaging were more likely to have node-positivity upon surgery, larger nodal metastases, and more frequent extranodal extension [108]. Digital Breast Tomosynthesis Diagnostic DBT allows visualization of axillary level I nodal regions but does not fully assess the axilla. Although not typically used for axillary evaluation, DBT may be helpful in evaluating for progression of the primary breast malignancy. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT for assessing a new palpable axillary mass during midtreatment of NAC. Mammography Diagnostic Similar to DBT, mammography does not visualize the entire axilla and is not useful for assessing an axillary lump. Mammography may be performed to determine if there is also progression of the primary breast carcinoma. Imaging of the Axilla MRI Breast There is no evidence to support the use of breast MRI as the initial imaging test for assessing a new palpable axillary lump during NAC treatment. However, breast MRI may be helpful in assessing response of the primary breast tumor and associated axillary adenopathy. Sestamibi MBI There is no relevant literature supporting the use of Tc-99m sestamibi MBI for assessing a new palpable axillary lump during midtreatment of NAC. US Axilla Despite the limited literature addressing the use of axillary US for assessing a new palpable axillary lump during midtreatment, axillary US may be useful in this scenario because of its noninvasive nature. If the axillary US finding is uncertain, biopsy can be performed [86].