Imaging After Shoulder Arthroplasty PCAs. Fracture confirmation can also be identified with anatomic imaging (eg, radiographs, CT with metal artifact reduction techniques). Normal uncomplicated postoperative change tends to decrease over time and up to 2 years or longer after surgery [21,22], whereas aseptic loosening generally tends to progress. Discordant activity of increased labeled WBC and a photopenic bone marrow is consistent with acute osteomyelitis. 3-Phase Bone Scan and WBC Scan and Sulfur Colloid Scan with SPECT or SPECT/CT Shoulder The use of nuclear imaging for the evaluation of periprosthetic infection has been limited to the evaluation of hip and knee arthroplasties, but various clinical studies anecdotally suggest utilizing this modality in shoulder arthroplasties [30]. Tc-99m 3-phase bone scan is a highly sensitive modality for the detection of acute osteomyelitis in the setting of normal radiographs but remains low in specificity because the imaging findings can overlap with other abnormalities such as mechanical loosening and osteolysis [30]. In addition, increased bone uptake can be seen at the site of arthroplasty, related to postoperative bone remodeling, for up to 1 year following surgery [30]. A bone scan is also limited in its ability to assess the periprosthetic soft tissues for the presence of an abscess. The addition of a bone scan SPECT/CT improves contrast resolution and anatomic localization of radiopharmaceutical uptake and provides a limited CT in the area of concern. A blood pool SPECT/CT over the targeted clinical area can be obtained immediately after the static blood pool images and further localizes foci of hyperemia [31-33]. At 2 to 3 hours after radiopharmaceutical administration and the standard bone scan images, a second SPECT/CT over the area(s) of interest can localize new bone formation [30] but remains nonspecific. A positive 3-phase bone scan can be seen in periprosthetic infection, periprosthetic fracture, and in the early postoperative state.


Imaging After Shoulder Arthroplasty PCAs. Postoperative change and fracture healing tend to decrease over time. Fracture confirmation can also be identified with anatomic imaging (eg, radiographs, CT with metal artifact reduction techniques). Normal uncomplicated postoperative change tends to decrease over time and up to 2 years or longer after surgery [21,22], whereas aseptic loosening generally tends to progress. The specificity of bone scans increases in older prostheses once the postoperative remodeling has stabilized. The addition of SPECT/CT with the In-111 WBC and sulfur colloid scans increases contrast resolution and anatomic localization of radiopharmaceutical activity. Utilizing subtraction imaging on the SPECT/CT studies (subtracting the sulfur colloid from WBC images) can identify whether an area of concern on the bone scan is concordant with similar increased WBC and marrow activity (reactive marrow) or discordant (WBC activity with absent sulfur colloid activity), the latter consistent with an acute pyogenic process/osteomyelitis. 3-Phase Bone Scan with SPECT or SPECT/CT Shoulder The use of nuclear imaging for the evaluation of periprosthetic infection has been limited to the evaluation of hip and knee arthroplasties, but various clinical studies anecdotally suggest utilizing this modality in shoulder arthroplasties [30]. Imaging After Shoulder Arthroplasty Tc-99m 3-phase bone scan is a highly sensitive modality for the detection of acute osteomyelitis in the setting of normal radiographs but remains low in specificity as the imaging findings can overlap with other abnormalities such as mechanical loosening and osteolysis [30]. In addition, increased bone uptake can be seen at the site of arthroplasty, related to postoperative bone remodeling, for up to 1 year following surgery [30]. A bone scan is also limited in its ability to assess the periprosthetic soft tissues for the presence of an abscess.


Imaging After Shoulder Arthroplasty PCAs. The addition of SPECT or SPECT/CT improves anatomic localization of new bone formation [20] but remains nonspecific. A positive 3-phase bone scan can be seen in periprosthetic infection, periprosthetic fracture, and in the early postoperative state. Postoperative change and fracture healing tend to decrease over time. Fracture confirmation can also be identified with anatomic imaging (eg, radiographs, CT with metal artifact reduction techniques). Normal uncomplicated postoperative change tends to decrease over time and up to 2 years or longer after surgery [21,22], whereas aseptic loosening generally tends to progress. The specificity of bone scans increases in older prostheses once the postoperative remodeling has stabilized. Image-Guided Aspiration Shoulder Aspiration of the shoulder should be performed when there is suspicion for an infected shoulder arthroplasty clinically, with or without radiographic evidence of infection, to avoid the destructive soft-tissue and bone changes that can result from an untreated infection. Imaging-guided aspiration procedures provide a minimally invasive means to sample fluid from the joint suspected of infection [34,35]. Shoulder joint aspiration has been shown to have a sensitivity of 33% and specificity of 98% [36]. Shoulder aspiration can be completed with the use of fluoroscopy, US, and CT guidance. MR guidance is possible but rarely utilized. Arthrography can be performed along with aspiration, when done under fluoroscopy and CT, to confirm the intra-articular origin of any aspirated fluid as well as to assess for any extension of the infectious process into adjacent bursae, sinus tracts, and abscesses [34]. Bone Scan Shoulder The use of nuclear imaging for the evaluation of periprosthetic infection has been limited to the evaluation of hip and knee arthroplasties, but various clinical studies anecdotally suggest utilizing this modality in shoulder arthroplasties [30].


Imaging After Shoulder Arthroplasty PCAs. The standard Tc-99m bone scan is a sensitive modality for the identification of abnormal bone in acute osteomyelitis, particularly in the setting of normal radiographs. However, the 3-phase bone scan is often preferred to assess for associated hyperemia in acute fracture and acute osteomyelitis. Bone scans remain low in specificity as the imaging findings can overlap with other abnormalities, such as mechanical loosening with osteolysis [30], periprosthetic fracture, and postarthroplasty bone remodeling, which can be seen up to 1 year following surgery [30]. Postoperative change and fracture healing tend to decrease over time. Fracture confirmation can also be identified with anatomic imaging (eg, radiographs, CT with metal artifact reduction techniques). Normal uncomplicated postoperative change tends to decrease over time and up to 2 years or longer after surgery [21,22], whereas aseptic loosening generally tends to progress. The specificity of bone scans for periprosthetic fracture or infection increases in older prostheses once the postoperative remodeling has stabilized. CT Shoulder CT with metal reduction protocols can elucidate the findings seen on radiographs and can further narrow the differential diagnosis in a patient suspected of periprosthetic infection as well as assist in preoperative planning [3]. CT may play a more important role after removal of the hardware and debridement in a patient with infection because it can help quantify the amount of remaining bone that can be used for revision arthroplasty [3]. CT can also be used to evaluate the surrounding soft tissues for infection and to aid in planning before image-guided joint aspiration. Administration of intravenous (IV) contrast improves the evaluation of adjacent soft-tissue fluid collections/abscesses and sinus tracts.


Imaging After Shoulder Arthroplasty PCAs. Fluoride PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of fluoride PET/CT for the next imaging study of a symptomatic patient with a primary shoulder arthroplasty when infection has been not excluded. MRI Shoulder MRI with metal reduction protocols can play a useful role in the diagnosis [37,38] and assessment of periprosthetic infection, particularly when other modalities fail to confirm the clinical suspicion of infection. MRI can demonstrate osseous and soft-tissue abnormalities associated with periprosthetic infection [28,39]. MRI can depict marrow edema suggestive of osteomyelitis. It can depict bony destruction, which can be difficult to note on radiographs, Imaging After Shoulder Arthroplasty related to osteomyelitis. MRI can also demonstrate joint effusions, adjacent soft-tissue edema, and fluid loculations suggestive of abscesses. Administration of IV contrast improves the evaluation of adjacent soft-tissue fluid collections/abscesses and sinus tracts. US Shoulder US examinations are increasingly being ordered for evaluation of periprosthetic infection in the setting of shoulder arthroplasty to evaluate for joint effusion and surrounding soft-tissue infection. US may be of use for the evaluation of a joint effusion, bursal distention, and the surrounding soft-tissues for signs of infection including abscesses [40- 42], which need aspiration and testing to determine the presence of infection and identification of the underlying microorganism. US is useful to evaluate the surrounding soft tissues for infection and to aid in planning before image-guided joint aspiration in order to avoid seeding of a sterile joint effusion from overlying soft-tissue infection. WBC Scan and Sulfur Colloid Scan Shoulder For infection imaging, In-111 WBC imaging in conjunction with Tc-99m sulfur colloid marrow imaging is a sensitive and specific test.


Imaging After Shoulder Arthroplasty PCAs. An isolated In-111-labeled WBC study is a sensitive but nonspecific technique for the evaluation of acute neutrophilic dominant periprosthetic infection [11]. Its specificity can be increased when interpreted alongside Tc-99m sulfur colloid imaging or, less optimally, bone scan imaging; the latter may not be indicated if both In-111 WBC and sulfur colloid imaging have been performed [11,21,30]. Variant 4: Symptomatic patient with a primary shoulder arthroplasty, infection excluded. Suspected loosening. Additional imaging following radiographs. Aseptic loosening, also referred to as mechanical loosening, is used to describe a hardware abnormality that results from a noninfectious etiology. One of the most common causes of aseptic loosening is osteolysis, a foreign-body response to debris that results from wear and breakdown of the hardware components, such as the acetabular polyethylene liner, cement, and/or metallic elements. Osteolysis can cause extensive, often asymptomatic, bone loss [43-45]. Although this process has been described extensively in the literature for hip arthroplasty, the literature on the topic is sparse in patients with shoulder arthroplasties [23,46]. 3-Phase Bone Scan with SPECT or SPECT/CT Shoulder Tc-99m 3-phase bone scan is a highly sensitive modality for the detection of acute osteomyelitis in the setting of normal radiographs but remains low in specificity because the imaging findings can overlap with other abnormalities, such as mechanical loosening with osteolysis and periprosthestic fracture [30]. In addition, increased bone uptake can be identified at the site of arthroplasty, related to postoperative bone remodeling, and seen for up to 1 year following surgery [30]. The addition of SPECT or SPECT/CT improves anatomic localization of active bone remodeling [20], however, remains nonspecific.


Imaging After Shoulder Arthroplasty PCAs. A positive 3-phase bone scan can be seen in the early postoperative state, periprosthetic fracture, aseptic prosthetic loosening, and periprosthetic infection. Postoperative change and fracture healing tend to decrease over time. Fracture confirmation can also be identified with anatomic imaging (eg, radiographs, CT with metal artifact reduction techniques). SPECT/CT also has the potential to differentiate symptomatic from asymptomatic scapular notching associated with reverse shoulder prostheses [30]. Normal uncomplicated postoperative change tends to decrease over time and up to 2 years or longer after surgery [21,22], whereas aseptic loosening generally tends to progress. The specificity of bone scans for periprosthetic complications increases in older prostheses once the postoperative remodeling has stabilized. Bone Scan Shoulder Tc-99m single-phase bone scan imaging is a sensitive modality for the diagnosis of loosening in the setting of normal radiographs but remains low in specificity because the imaging findings can overlap with other abnormalities such as postoperative bone remodeling, periprosthetic fracture, and infection [30]. Normal uncomplicated increased periprosthetic uptake related to postoperative bone remodeling tends to decrease over time and up 2 years or longer after surgery [21,30], whereas aseptic loosening generally tends to progress. The specificity of bone scans for periprosthetic fracture, loosening, or infection increases in older prostheses once the postoperative remodeling has stabilized. CT Shoulder CT plays an important role in the imaging evaluation of a patient with potential loosening that may be missed or incompletely evaluated with radiographs [10,47]. CT provides a better means of evaluating the hardware components and surrounding bone stock [48]. CT can also assess changes in component alignment over time [49].


Imaging After Shoulder Arthroplasty PCAs. Imaging After Shoulder Arthroplasty Image degradation can occur because of beam hardening artifact and other hardware-related artifacts, especially with older CT scanners. The use of newer metal reduction CT software has decreased the artifact-related limitations, improving evaluation [50-52]. Furthermore, dual-energy CT, employing virtual noncalcium software, may provide useful information regarding the presence of marrow edema [53]. CT can also be used to evaluate the bone density around prostheses, which may be predictive of loosening [54]. Metal reduction protocols and modifications in patient positioning have greatly enhanced the ability of CT to evaluate for complications associated with shoulder arthroplasties. Nevertheless, there are scant studies assessing the benefit of CT in patients with postoperative complications. In a few reports, each including a small group of patients, CT compared with radiographs, has been found to better demonstrate imaging findings such as periprosthetic lucency, osteolysis, hardware malposition, and component migration, as well as the degree of osseous incorporation along the glenoid, deficiency of which has been associated with the risk of failure [10,47,55]. Evaluation of bone graft resorption remains limited on CT because of metal artifact [56]. Dual-energy CT virtual noncalcium techniques, although not yet specifically studied in the postoperative shoulder, may potentially provide useful information about marrow edema associated with the above abnormalities [53]. The addition of intra-articular or IV contrast does not typically improve evaluation [57]. Fluoride PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of fluoride PET/CT after radiographs in a symptomatic patient with a primary shoulder arthroplasty and infection was excluded.


Imaging After Shoulder Arthroplasty PCAs. MRI Shoulder Evolving MRI methods with improved image quality and metal artifact reduction have rendered the modality a more feasible technique for the diagnosis of component loosening, rotator cuff tearing, and, in the presence of hemiarthroplasty, glenoid cartilage wear [37-39,58]. Because of developments in metal reduction protocols for MRI and research studies showing the benefit of MRI, it can be effective in the evaluation of aseptic loosening [37-39]. US Shoulder US is limited in the ability to evaluate bone-related complications such as loosening [10]. Variant 5: Symptomatic patient with a primary shoulder arthroplasty, infection excluded. Suspected rotator cuff tear or other soft-tissue abnormality. Additional imaging following radiographs. The prevalence of rotator cuff tears after arthroplasty placement has been reported to be up to 1.3% [3]. Tears of the subscapularis tendon can present with clinical and radiographic signs of anterior shoulder instability, including varying degrees of anterior subluxation as well as frank dislocation of the humeral head component relative to the glenoid [6,10]. 3-Phase Bone Scan with SPECT or SPECT/CT Shoulder Nuclear medicine examinations are not typically ordered for the evaluation of rotator cuff tendon abnormalities. Bone Scan Shoulder Nuclear medicine examinations are not typically ordered for the evaluation of rotator cuff tendon abnormalities. CT Arthrography Shoulder The inherent limited tissue-contrast resolution of CT detracts from its ability to detect rotator cuff tears. A CT arthrogram can be performed when there is suspicion of a rotator cuff tear [10]. CT arthrography can be an effective modality to evaluate the rotator cuff and detect any associated pathology [10,59]. The technique, however, is relatively weak in its ability to assess the extent of partial rotator cuff tears as well in identifying the exact location of the tear when compared with MRI.


Imaging After Shoulder Arthroplasty PCAs. The presence and degree of fatty muscle replacement can also be used as an indirect sign of a rotator cuff tear [60,61]. Administration of IV contrast does not improve evaluation. CT Shoulder The inherent limited tissue-contrast resolution of CT detracts from its ability to detect rotator cuff tears. CT shows promise in assessing the location of the glenoid and humeral components of reverse shoulder prostheses in the setting of soft-tissue impingement [62]. Administration of IV contrast does not improve evaluation. Fluoride PET/CT Skull Base to Mid-Thigh Nuclear medicine examinations are not typically ordered for the evaluation of rotator cuff tendon abnormalities. Imaging After Shoulder Arthroplasty MRI Shoulder Evolving MRI methods with improved image quality and metal artifact reduction have rendered the modality a more feasible technique for the diagnosis of component loosening, rotator cuff tearing, and, in the presence of hemiarthroplasty, glenoid cartilage wear [37-39,58]. MRI can be used to evaluate for rotator cuff tendon tearing in the setting of shoulder arthroplasty [38,39]. Advanced metal reduction techniques can reduce the prosthesis-related artifact and thus improve visualization of the rotator cuff tendons and any associated pathology [37,38]. Compared with the other imaging techniques, MRI can also provide a more global evaluation of the arthroplasty components as well as the surrounding soft tissues [37,38]. MRI with metal reduction techniques can also demonstrate failure of subscapularis tendon repair in the setting of arthroplasty, the most common location for rotator cuff pathology in this setting [38]. There are multiple techniques used to release the subscapularis tendon during arthroplasty placement, including tenotomy, osteotomy, and peel [10].


Sinonasal Disease

Sinonasal Disease.  Introduction/Background According to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), the term rhinosinusitis refers to symptomatic inflammation of the nasal cavity and paranasal sinuses and is preferred over the term sinusitis, because inflammation of the nasal cavity nearly always accompanies inflammation of the contiguous paranasal sinuses. Rhinosinusitis may be classified as acute rhinosinusitis (ARS) if symptoms last <4 weeks or as chronic rhinosinusitis (CRS) if symptoms last >12 weeks [1]. Patients with acute bacterial rhinosinusitis (ABRS) may develop orbital, intracranial, and vascular complications, including orbital cellulitis, subperiosteal abscess, intracranial abscess, cerebritis, cavernous sinus thrombosis, and aneurysm. Acute recurrent rhinosinusitis refers to when patients have 4 or more episodes of rhinosinusitis per year without persistent symptoms between episodes. CRS is one of the most common chronic illnesses in the United States, affecting approximately 12% to 16% of the population [2], with an overall annual economic burden estimated at $22 billion [3]. Acute invasive fungal sinusitis is a fungal infection of the paranasal sinuses with a rapid time course of <4 weeks [4] and a high mortality rate of 50% to 80% [5,6]. Affected patients are typically immunocompromised and include patients with neutropenia, hematologic malignancies, poorly controlled diabetes, acquired immunodeficiency syndrome, organ transplantation, and patients on immunosuppressive therapy including systemic steroids and chemotherapy [4]. Presenting symptoms are nonspecific and include fever, rhinorrhea, and diplopia, similar to those seen with ABRS. Clinicians should maintain a high index of suspicion for this diagnosis in immunocompromised patients with symptoms of ARS, orbital symptoms, and/or headache. [4]. Sinonasal neoplasms account for 3% of head and neck neoplasms [7].


Sinonasal Disease

Sinonasal Disease. Patients with a sinonasal mass may present with nasal congestion, nasal fullness, anosmia, rhinorrhea, and epistaxis [8,9]. Benign lesions include papilloma, respiratory epithelial adenomatoid hamartoma, pleomorphic adenoma, juvenile nasopharyngeal angiofibroma, nerve sheath tumor, and meningioma [7,8]. The most common sinonasal malignancy is squamous cell carcinoma, with other malignancies lymphoma, neuroendocrine tumors, salivary gland tumors, and melanoma [7,10]. aNew York University Langone Health, New York, New York. bPanel Chair, University of Iowa Hospitals and Clinics, Iowa City, Iowa. cPanel Vice-Chair, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts. dFroedtert Memorial Lutheran Hospital Medical College of Wisconsin, Milwaukee, Wisconsin. eMontefiore Medical Center, Bronx, New York. fHouston Methodist Hospital, Houston, Texas. gUniversity of Texas Health Science Center, Houston, Texas. hThe University of Texas MD Anderson Cancer Center, Houston, Texas. iMetroHealth Medical Center, Cleveland, Ohio. jEastern Virginia Medical School, Norfolk, Virginia; American Academy of Otolaryngology-Head and Neck Surgery. kUniversity of Texas Health Science Center, Houston, Texas. lMayo Clinic Arizona, Phoenix, Arizona. mUniversity of Iowa Carver College of Medicine, Iowa City, Iowa, Primary care physician. nUniversity of Otago, Dunedin, Otepoti, New Zealand. oGeorge Washington University Hospital, Washington, District of Columbia. pUniversity of Colorado Denver, Denver, Colorado. qSpecialty Chair, Atlanta VA Health Care System and Emory University, Atlanta, Georgia. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization.


Sinonasal Disease

Sinonasal Disease. Reprint requests to: publications@acr.org Arteriography Craniofacial There is no relevant literature to support the use of arteriography in the evaluation of acute uncomplicated rhinosinusitis. CT Cone Beam Paranasal Sinuses As per clinical practice guidelines from the AAO-HNS, CT imaging of the sinuses is unnecessary for patients with a clinical diagnosis of ARS [1]. CT has not been shown to accurately distinguish ABRS from ARS of viral etiology [1,17,18]. Moreover, cone beam CT (CBCT) is limited in the evaluation of the soft tissues and is therefore not helpful in the imaging assessment of complications of sinus disease [19]. CT Head As per clinical practice guidelines from the AAO-HNS, imaging is unnecessary for patients with a clinical diagnosis of ARS [1]. There is no relevant literature to support the use of CT head in the evaluation of acute uncomplicated rhinosinusitis. CT Maxillofacial As per clinical practice guidelines from the AAO-HNS, CT imaging of the sinuses is unnecessary for patients with a clinical diagnosis of ARS [1]. CT has not been shown to accurately distinguish ABRS from ARS of viral etiology [1,17,18]. CTA Head There is no relevant literature to support the use of CT angiography (CTA) head in the evaluation of acute uncomplicated rhinosinusitis. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT in the evaluation of acute uncomplicated rhinosinusitis. MRA Head There is no relevant literature to support the use of MR angiography (MRA) head in the evaluation of acute uncomplicated rhinosinusitis. Sinonasal Disease MRI Head As per clinical practice guidelines from the AAO-HNS, imaging is unnecessary for patients with a clinical diagnosis of ARS [1]. There is no relevant literature to support the use of MRI head in the evaluation of acute uncomplicated rhinosinusitis.


Sinonasal Disease

Sinonasal Disease. MRI Orbits, Face, and Neck As per clinical practice guidelines from the AAO-HNS, imaging is unnecessary for patients with a clinical diagnosis of ARS [1]. There is no relevant literature to support the use of MRI of the orbits, face, and neck in the evaluation of acute uncomplicated rhinosinusitis. Radiography Paranasal Sinuses As per clinical practice guidelines from the AAO-HNS, imaging of the sinuses is unnecessary for patients with a clinical diagnosis of ARS [1]. Radiography lacks specificity for the identification of ABRS, because sinus fluid can also be seen with viral upper respiratory tract infections [20]. Compared with CT, radiography has been shown to have a low sensitivity of 25% to 41% for all sinus groups except the maxillary sinuses with 80% sensitivity [21]. In a meta-analysis of 6 studies, radiographs of the paranasal sinuses demonstrated a sensitivity of 76% and specificity of 79% for the diagnosis of ABRS compared with sinus puncture [22]. SPECT or SPECT/CT Paranasal Sinuses There is no relevant literature to support the use of single-photon emission CT (SPECT) or SPECT/CT in the evaluation of acute uncomplicated rhinosinusitis. Variant 2: Acute rhinosinusitis with suspected orbital or intracranial complication. Initial imaging. ABRS may spread to the orbital and intracranial compartments through neurovascular foramina, areas of osseous erosion, or hematogenous spread along valveless veins [6]. Orbital complications are more common and include orbital cellulitis, subperiosteal abscess, and orbital abscess. Symptoms suggesting orbital involvement include eye swelling with or without proptosis, impaired eye movement, and decreased visual acuity [17,23]. Intracranial complications most commonly occur with frontal sinusitis and include epidural abscess, subdural empyema, cerebritis, brain abscess, and meningitis. Symptoms suggesting intracranial involvement include severe headache, photophobia, seizures, or other focal neurologic findings [6,17].


Sinonasal Disease

Sinonasal Disease. Vascular complications include cavernous sinus thrombosis and rarely pseudoaneurysm formation [2,24]. Arteriography Craniofacial Arteriography may be performed for the evaluation of a pseudoaneurysm, although this would not be performed in the initial imaging evaluation. There is no relevant literature to support the use of arteriography in the evaluation of ARS with suspected orbital or intracranial complication. CT Cone Beam Paranasal Sinuses CBCT is not helpful in the imaging assessment of patients with ARS with suspected orbital or intracranial complications because of a limited evaluation of the soft-tissue structures [19,25]. CT Head CT maxillofacial is useful as the first-line CT examination for patients with ARS with suspected intraorbital and intracranial complications, because complications adjacent to the paranasal sinuses are typically included in the field of view. MRI is overall more useful than CT for the evaluation of intracranial complications, but because CT may be the first imaging study ordered, contrast-enhanced CT head may be added to the CT maxillofacial examination for increased coverage of a suspected intracranial complication. CT head with intravenous (IV) contrast can accurately identify clinically suspected intracranial complications including epidural abscess, subdural empyema, cerebritis, and brain abscess. The accuracy for the detection of intracranial complications has been reported to be 87% for CT, compared with 97% for MRI [23], although the detection of cavernous sinus thrombosis, meningitis, and early cerebritis is more difficult on CT compared with MRI [6,17,23]. There is no relevant literature to support the use of noncontrast CT head or combined pre- and postcontrast CT imaging. CT Maxillofacial CT of the paranasal sinuses with IV contrast can accurately confirm paranasal sinus inflammation and identify orbital complications and adjacent intracranial complications included in the field of view [17].


Sinonasal Disease

Sinonasal Disease. Given its detailed depiction of bony anatomy, CT can also accurately demonstrate the presence of erosions of the sinus and orbital walls. Studies have demonstrated a higher accuracy of CT compared with clinical examination for detecting orbital complications, with an accuracy of 87% to 91% [23]. CT also enables surgical planning given its detailed depiction Sinonasal Disease of sinonasal anatomy and can be used for surgical image-guidance systems. Although MRI is overall more useful than CT for the evaluation of intracranial and intraorbital complications, CT is often the first imaging study ordered. A noncontrast CT may be performed for bony evaluation and surgical planning but is limited in the detection of orbital and intracranial complications. There is no relevant literature to support the use of combined pre- and postcontrast CT imaging. CTA Head CTA head may be performed for the evaluation of a pseudoaneurysm, but this is typically not performed in the initial imaging evaluation. There is no relevant literature to support the use of CTA head in the evaluation of ARS with suspected orbital or intracranial complication. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT in the evaluation of ARS with suspected orbital or intracranial complication. MRA Head MRA head may be performed for the evaluation of a pseudoaneurysm, but this is typically not performed in the initial imaging evaluation. There is no relevant literature to support the use of MRA head in the evaluation of ARS with suspected orbital or intracranial complication. MRI Head MRI head without and with IV contrast can accurately identify clinically suspected intracranial complications including cavernous sinus thrombosis, epidural abscess, subdural empyema, cerebritis, brain abscess, and meningitis, with a reported 97% diagnostic accuracy compared with 87% for CT and a superior accuracy in particular for the diagnosis of meningitis [17,23].


Sinonasal Disease

Sinonasal Disease. Combined pre- and postcontrast imaging provides the best opportunity to identify and characterize potential intracranial complications. Restricted diffusion on diffusion- weighted sequences can accurately identify the presence of purulent material within extra-axial collections and brain abscesses. MRI Orbits, Face, and Neck MRI orbits, face, and neck without and with IV contrast can confirm paranasal sinus inflammation and identify orbital complications and adjacent intracranial complications included in the field of view [17]. This study may be done in conjunction with MRI head for suspected orbital and intracranial complications. Although noncontrast imaging can demonstrate fluid collections and edema, combined pre- and postcontrast imaging provides the best opportunity to identify and characterize potential orbital and intracranial complications. Radiography Paranasal Sinuses There is no relevant literature to support the use of radiography in the evaluation of ARS with suspected orbital or intracranial complication. Radiography is limited in the evaluation of soft-tissue structures. SPECT or SPECT/CT Paranasal Sinuses There is no relevant literature to support the use of SPECT or SPECT/CT in the evaluation of ARS with suspected orbital or intracranial complication. Variant 3: Acute recurrent sinusitis or chronic rhinosinusitis or noninvasive fungal sinusitis or sinonasal polyposis. Possible surgical candidate for these indications or other non-neoplastic indications, including suspected silent sinus syndrome or suspected mucocele, or deviated nasal septum. Initial imaging. CRS refers to rhinosinusitis lasting >12 weeks, and the most common symptoms of CRS include nasal obstruction, facial congestion and pressure, discolored nasal discharge, and hyposmia [26].


Sinonasal Disease

Sinonasal Disease. The presence of 2 or more of these symptoms for >12 weeks is highly sensitive for the diagnosis of CRS, but because these symptoms are nonspecific, documentation of inflammation on endoscopy or imaging is required to confirm the diagnosis [26]. Imaging findings that confirm CRS include mucosal thickening, sinus opacification, polyps or retention cysts, and sclerosis and thickening of the sinus walls [2,26]. Studies have shown variable correlation between the imaging findings and clinical symptoms of CRS. The Lund- Mackay and modified Lund-Mackay system are the most commonly used imaging staging systems, with some studies showing good correlation with disease severity and surgical outcomes [2,27,28]. Some studies have not demonstrated a correlation between symptom severity and CT findings [29-31], although correlation may be higher in patients with associated nasal polyps [29]. Sinonasal Disease Functional endoscopic sinus surgery is now the standard of care for restoring patency of paranasal sinus outflow tracts, with postoperative improvement in symptoms and quality of life reported in over 75% of patients [32]. Functional endoscopic sinus surgery may be performed for CRS and other nonneoplastic indications including acute recurrent rhinosinusitis, noninvasive fungal sinusitis and fungus ball, sinonasal polyposis, silent sinus syndrome, mucocele, and deviated nasal septum. Imaging that provides anatomical detail is needed for surgical planning, in particular for the identification of anatomic variants and abnormalities that can increase the risk for intracranial, intraorbital, and vascular injury. Arteriography Craniofacial There is no relevant literature to support the use of arteriography in the evaluation of CRS or for presurgical planning of paranasal sinus inflammatory disease. CT Cone Beam Paranasal Sinuses CBCT has been shown to have high accuracy for evaluating odontogenic and nonodontogenic sinusitis, with strong agreement between CBCT and sinus endoscopy [33].


Sinonasal Disease

Sinonasal Disease. Similar to standard multidetector CT, CBCT can confirm the diagnosis of CRS and identify anatomic variants for presurgical planning. One study showed decreased detection of intrasinus calcifications in patients with noninvasive fungal sinusitis compared with multidetector CT, although comparison between the 2 modalities was done in separate patient cohorts [34]. CBCT is limited in the evaluation of soft-tissue structures and therefore is not the imaging modality of choice if extrasinus disease is suspected [19,25]. CT Head Given its typical incomplete coverage of the paranasal sinuses, CT head is not typically performed for the evaluation of CRS or for presurgical planning of paranasal sinus inflammatory disease. CT Maxillofacial Given its excellent bony detail, multidetector CT without IV contrast is useful for confirming and evaluating CRS and for presurgical planning. Imaging findings that confirm CRS include mucosal thickening, sinus opacification, polyps or retention cysts, and sclerosis and thickening of the sinus walls [2,26]. CT has been shown to accurately identify these findings of CRS, although the findings have been shown to not necessarily correlate with the severity of symptoms [26]. CT can also evaluate the extent of disease and identify anatomic variants that narrow sinus drainage pathways [32]. CT is critical for surgical planning, in particular for the identification of anatomic variants and abnormalities that can increase the risk for intracranial, intraorbital, and vascular injury as well as for CSF leak [31,32]. Low-dose techniques have been shown to be limited in the visualization of surgically relevant anatomical structures including the cribriform plates, lamina papyracea, and anterior ethmoidal artery canal in the setting of CRS with nasal polyps and a history of sinus surgery [35]. A sinus CT protocol that can be utilized by image guidance systems is recommended [36].


Sinonasal Disease

Sinonasal Disease. Contrast-enhanced CT is not necessary to demonstrate findings of CRS or for surgical planning of paranasal sinus inflammatory disease. There is no relevant literature to support the use of combined pre- and postcontrast CT imaging. Silent sinus syndrome is atelectasis of the maxillary sinus due to intrasinus negative pressure from chronic ostial obstruction. Both CT and MRI can demonstrate decreased maxillary sinus volume and inward bowing of the sinus walls characteristic of silent sinus syndrome, but additional findings of osseous thinning, obstruction of the infundibulum, and lateralization of the uncinate process are better delineated on CT compared with MRI [37]. Nasal septal deviation can cause symptomatic nasal obstruction and can also be a risk factor for CRS. Clinical anterior rhinoscopy and endoscopic examination is the reference standard for evaluating nasal septal deviation. CT has been shown to have limited correlation with physical examination, and CT may underestimate the degree of nasal obstruction due to septal deviation at the internal nasal valve. CT therefore should not be performed solely for the evaluation of septal deviation but rather for the evaluation of any associated symptoms of CRS [38]. CTA Head There is no relevant literature to support the use of CTA head in the evaluation of CRS or for presurgical planning of paranasal sinus inflammatory disease. Sinonasal Disease FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT in the evaluation of CRS or for presurgical planning of paranasal sinus inflammatory disease. MRA Head There is no relevant literature to support the use of MRA head in the evaluation of CRS or for presurgical planning of paranasal sinus inflammatory disease. MRI Head There is no relevant literature to support the use of MRI head in the evaluation of CRS or for presurgical planning of paranasal sinus inflammatory disease.


Sinonasal Disease

Sinonasal Disease. MRI Orbits, Face, and Neck MRI is not useful as the first-line study for routine sinus imaging because of the lack of bony detail. In addition, inspissated secretions may demonstrate a signal void that mimics air on T2-weighted sequences [39]. However, one study examined 89 adult patients imaged with both CT and MRI within a 3-month period for evaluation of pituitary disease and showed significant correlation between CT and MRI based Lund-Mackay staging scores of sinus disease; T1- and T2-weighted sequences were utilized for MRI scoring [40]. The utilization of IV contrast was not specified, and the Lund-Mackay scores were not correlated with patient symptoms in this study. In select cases, evaluation with MRI without and with IV contrast may be helpful to differentiate fluid secretions from inflamed mucosa and exclude an underlying obstructing mass [24]. Radiography Paranasal Sinuses Detection of mucosal thickening is limited on radiography because of overlapping osseous structures [41]. CT has largely replaced radiography given its superior depiction of sinonasal anatomy and pathology and the need for greater anatomic detail for functional endoscopic sinus surgery planning [2,41]. SPECT or SPECT/CT Paranasal Sinuses In a pilot study of 24 patients with CRS, a positive SPECT correlated with more extensive disease on CT and poor subjective response to medical treatment [42]. However, the use of SPECT remains limited in the evaluation of CRS, and this technique is generally not used in clinical practice. Variant 4: Acute sinusitis with rapid progression or suspected invasive fungal sinusitis. Initial imaging. Acute invasive fungal sinusitis is a fungal infection of the paranasal sinuses with a rapid time course of <4 weeks [4] and a high mortality rate of 50% to 80% [5,6].


Sinonasal Disease

Sinonasal Disease. Affected patients are typically immunocompromised and include patients with neutropenia, hematologic malignancies, poorly controlled diabetes, acquired immunodeficiency syndrome, and organ transplantation and patients on immunosuppressive therapy including systemic steroids and chemotherapy [4,5]. Aspergillus and Mucoraceae species are seen in most cases. Presenting symptoms are nonspecific and include fever, rhinorrhea, and diplopia, similar to those seen with ABRS. Clinicians should maintain a high index of suspicion for this diagnosis in immunocompromised patients with symptoms of ARS, orbital symptoms, and/or headache. Nasal endoscopy may demonstrate pale mucosa progressing to ulceration and necrosis [4]. Definitive diagnosis is made on biopsy with the identification of invasive fungi in the sinonasal mucosa, vessels, and bone [4]. Given the angioinvasive nature of the fungi, complications include thrombosis, dissection, and pseudoaneurysm formation of the intracranial arteries, thrombosis of the cavernous sinus, infarction, and hemorrhage [4,6]. Treatment typically includes both systemic antifungal medication and surgical debridement. Arteriography Craniofacial Arteriography may be performed for further characterization and confirmation of vascular complications of invasive fungal sinusitis detected by MRI, MRA, or CTA, including pseudoaneurysm formation, thrombosis, and dissection, although this would not be performed in the initial imaging evaluation. There is no relevant literature to support the use of arteriography in the initial evaluation of suspected acute invasive fungal sinusitis. CT Cone Beam Paranasal Sinuses CBCT is not helpful in the imaging assessment of patients with ARS with suspected orbital or intracranial complications because of the limited evaluation of the soft-tissue structures [19,25]. Sinonasal Disease CT Head CT head with IV contrast may be used to demonstrate intracranial complications but is less sensitive compared with MRI [6,23,43].


Sinonasal Disease

Sinonasal Disease. There is no relevant literature to support the use of noncontrast CT head or combined pre- and postcontrast CT imaging. CT Maxillofacial Noncontrast CT is effective in the evaluation of fungal sinusitis because it can demonstrate hyperattenuation in the involved sinus, bony erosions, and infiltration of the surrounding spaces [4,44]. Hyperattenuation within the paranasal sinuses can suggest the diagnosis but is nonspecific. Features including bone erosion and infiltration of the periantral fat have a high specificity but a limited sensitivity, particularly in the early phase of the disease, and severe predominantly unilateral nasal cavity mucosal thickening has a high sensitivity but low specificity [5,6,44]. In a retrospective study evaluating 42 patients with pathology-proven acute invasive fungal rhinosinusitis and 42 control patients from the same high-risk population, a 7-variable model was synthesized using infiltration of the periantral fat, pterygopalatine fossa, nasolacrimal duct and lacrimal sac, bone dehiscence, septal ulceration, and orbital involvement; positive findings in any 2 of the model variables demonstrated 88% sensitivity and 100% specificity [44]. Emphysematous soft tissue in the nasal cavity is also a specific sign of early invasive fungal sinusitis [5]. CT also enables surgical planning given its detailed depiction of sinonasal anatomy and can be used with surgical image-guidance systems when acquired with the appropriate protocol. CT with IV contrast may also be used to help demonstrate orbital and intracranial complications included in the field of view. [6,23,43]. There is no relevant literature to support the use of combined pre- and postcontrast CT imaging. CTA Head CTA head may be performed for the evaluation of vascular complications of invasive fungal sinusitis including pseudoaneurysm formation, thrombosis, and dissection, although this would not be performed in the initial imaging evaluation.


Sinonasal Disease

Sinonasal Disease. There is no relevant literature to support the use of CTA head in the initial evaluation of suspected acute invasive fungal sinusitis. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT in the evaluation of acute invasive fungal sinusitis. MRA Head MRA head may be performed for the evaluation of vascular complications of invasive fungal sinusitis including pseudoaneurysm formation, thrombosis, and dissection, although this would not be performed in the initial imaging evaluation. There is no relevant literature to support the use of MRA head in the initial evaluation of suspected invasive fungal sinusitis. MRI Head MRI head without and with IV contrast can delineate complications involving the intracranial compartment better than CT [5,6,43]. Combined pre- and postcontrast imaging provides the best opportunity to identify and characterize potential intracranial complications. MRI head with and without IV contrast may be complementary to CT maxillofacial to identify intracranial spread beyond the field of view of the MRI orbits, face, and neck examination. MRI Orbits, Face, and Neck A T2 signal void from fungal concretions can be confused for a pneumatized sinus, limiting evaluation of intrasinus disease with MRI [4,5]. However, MRI without and with IV contrast provides accurate evaluation of the invasion of the surrounding soft tissues, orbits, and intracranial compartment and vascular complications. One study evaluating 17 immunocompromised patients with acute invasive fungal sinusitis and 6 controls found increased sensitivity of MRI of 85% to 86% compared with CT with a sensitivity of 57% to 69% and found extrasinus invasion to be the most sensitive imaging finding [4,45]. Lack of sinonasal mucosal and nasal turbinate enhancement, the latter described as the black turbinate sign, correlates with necrosis related to the angioinvasive nature of fungal sinusitis [4].


Sinonasal Disease

Sinonasal Disease. In a study from Korea evaluating 23 patients with acute invasive fungal rhinosinusitis, extrasinonasal extension was demonstrated in all cases on MRI, with orbital extension in 65%; lack of contrast enhancement was seen in 48% of patients and was found to be a prognostic factor for disease-specific mortality [46]. Although noncontrast imaging can demonstrate fluid collections and edema, combined pre- and postcontrast imaging provides the best opportunity to identify and characterize potential orbital, intracranial, and vascular complications. Sinonasal Disease Radiography Paranasal Sinuses Radiography of the paranasal sinuses is considered to be of limited usefulness given a large number of false-negative results [47]. Findings of bone erosion may be seen in advanced cases, but CT is more useful for the detection of bony erosion and adjacent soft-tissue involvement. SPECT or SPECT/CT Paranasal Sinuses There is no relevant literature to support the use of SPECT or SPECT/CT in the evaluation of acute invasive fungal sinusitis. Variant 5: Suspected sinonasal mass. Initial imaging. Patients with a sinonasal mass may present with nasal congestion, nasal fullness, anosmia, rhinorrhea, and epistaxis [8,9]. Benign lesions include papilloma, respiratory epithelial adenomatoid hamartoma, pleomorphic adenoma, juvenile nasopharyngeal angiofibroma, nerve sheath tumor, and meningioma [7,8]. The most common sinonasal malignancy is squamous cell carcinoma, with other malignancies including sinonasal undifferentiated carcinoma, adenocarcinoma, lymphoma, neuroendocrine tumors, salivary gland tumors, and melanoma [7,10]. A meningoencephalocele may also present as a sinonasal mass. Imaging may demonstrate specific features of a sinonasal mass, which can narrow a differential diagnosis and occasionally facilitate a specific diagnosis. Ultimately, very few imaging features are pathognomonic and most sinonasal neoplasms require histologic sampling for a specific diagnosis [7,24].


Sinonasal Disease

Sinonasal Disease. The main role of imaging in these cases is to delineate the extent of disease for treatment planning. Arteriography Craniofacial Catheter angiography is typically not useful in the initial imaging evaluation of a sinonasal mass. It may be useful for preoperative planning, preoperative embolization of a vascular mass, or to treat severe epistaxis [43,48-50]. CT Cone Beam Paranasal Sinuses CBCT is not useful in the workup of patients with sinonasal mass because of the limitations in assessing soft-tissue structures. CT Head CT best depicts osseous changes, although it is limited in determining soft-tissue and intracranial extent. Although MRI is useful for evaluating intracranial extension of a sinonasal mass, contrast-enhanced CT can also be useful for evaluating the soft-tissue and intracranial extent of the mass [51]. CT maxillofacial is useful as the first-line CT examination for suspected sinonasal mass, but contrast-enhanced CT head may be added if increased coverage of the intracranial component of a mass and its associated mass effect of the intracranial structures is required. There is no relevant literature to support the use of noncontrast CT head or combined pre- and postcontrast CT imaging. CT Maxillofacial CT best depicts osseous changes and can help distinguish bony remodeling that is more typical of slow growing or benign masses from lytic destruction seen with more aggressive malignancies [7,51]. CT can demonstrate lesion mineralization, including the osseous matrix of osteomas, the chondroid matrix of cartilaginous tumors, and the ground glass density of fibro-osseous lesions. CT also best depicts invasion of the surrounding osseous structures, although it is limited in determining soft-tissue and intracranial extent and in distinguishing tumor from sinonasal inflammation. CT and MRI are complementary imaging modalities in the evaluation of sinonasal masses, localizing and characterizing lesions and determining their extent for treatment planning.


Sinonasal Disease

Sinonasal Disease. If an MRI is also planned or performed, the CT can be performed without IV contrast because the main purpose of the CT is to evaluate osseous involvement. Although MRI is superior for evaluating the soft tissues, contrast-enhanced CT can also be useful for evaluating the soft-tissue and intracranial extent of the mass [51]. CT maxillofacial also enables surgical planning given its detailed depiction of sinonasal anatomy and can be used with surgical image-guidance systems when acquired with the appropriate protocol. CTA Head CTA head is typically not useful in the initial imaging evaluation of a sinonasal mass. It may be useful for preoperative planning of a vascular mass [43,48-50]. Sinonasal Disease FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT is not useful for the initial evaluation of a sinonasal mass but can be used to detect regional and distant metastases in the staging workup of malignant neoplasms [7]. MRA Head MRA head typically is not useful in the initial imaging evaluation of a sinonasal mass. It may be useful for preoperative planning of a vascular mass [43,48-50]. MRI Head MRI head may be performed in addition to the MRI maxillofacial examination if increased coverage of the intracranial component of a mass and its associated mass effect of the intracranial structures is required. Combined pre- and postcontrast imaging provides the best opportunity to identify intracranial extension and to characterize potential intracranial complications. MRI Orbits, Face, and Neck MRI without and with IV contrast can best characterize the soft-tissue components of a mass and can occasionally demonstrate signal characteristics suggestive of specific pathology. For example, MRI can demonstrate the convoluted cerebriform pattern of inverted papillomas on T2-weighted and contrast-enhanced T1-weighted MRI; the intrinsic T1 hyperintensity of melanotic melanomas; and peritumoral intracranial cysts, which are suggestive of, but not specific for, esthesioneuroblastoma [7,8].


Sinonasal Disease

Sinonasal Disease. Decreased T2 signal and apparent diffusion coefficient correlate with increased cellularity of tumors [9]. Perfusion MRI can also potentially provide diagnostic information of sinonasal masses [52,53]. For tumor mapping, MRI is more helpful than CT for soft tissue contrast and can better distinguish tumors from the more T2 hyperintense sinus inflammatory changes and retained secretions. MRI can also best identify intracranial and perineural involvement important for staging and presurgical planning [7,24]. Compared with CT, MRI can also better detect osseous marrow invasion. CT and MRI are complementary imaging modalities in the evaluation of sinonasal masses, localizing and characterizing lesions, and determining their extent for treatment planning. Radiography Paranasal Sinuses Radiography is not considered to be part of the imaging workup of sinonasal neoplasms [51]. SPECT or SPECT/CT Paranasal Sinuses There is no relevant literature to support the use of SPECT or SPECT/CT in the evaluation of a sinonasal mass. Arteriography Craniofacial There is no relevant literature to support the use of arteriography in the evaluation of sinonasal CSF leak. CT Cone Beam Paranasal Sinuses There is no relevant literature regarding the use of CBCT paranasal sinuses in the evaluation of sinonasal CSF leak. CT Head Cisternography CT head cisternography is performed by spinal injection of intrathecal contrast, with images performed before and after contrast administration. Interval contrast pooling adjacent to an osseous defect can be identified with demonstration of a 50% or greater increase in Hounsfield units between the pre- and postcontrast scans [12]. CT head cisternography is primarily used in the setting of multiple osseous defects on high-resolution CT (HRCT) to Sinonasal Disease determine the specific site of the leak [12]. CT cisternography has a reported sensitivity of 33% to 100% and a specificity of 94% [12,13,55-58].


Sinonasal Disease

Sinonasal Disease. The primary limitation of CT cisternography is that the patient needs to have an active CSF leak at the time of this examination for the study to be potentially diagnostic. Studies comparing CT cisternography with MRI have demonstrated CT cisternography to have a lower sensitivity of 33% to 72% versus 67% to 93% for MRI with a heavily T2-weighted sequence (MR cisternogram) and 80% for contrast-enhanced MR cisternogram [13,59,60]. CT Head Given its typical incomplete coverage of the paranasal sinuses, CT head is not typically performed for the evaluation of sinonasal CSF leak. HRCT also enables surgical planning given its detailed depiction of sinonasal anatomy and can be used with surgical image-guidance systems when acquired with the appropriate protocol. HRCT can identify the skull base defect even in the absence of an active leak; however, it is limited in identifying a specific site of the leak if the patient has multiple osseous defects because it is not clear which defect is the source of the leak [12]. A combination of HRCT and MRI with a heavily T2-weighted sequence has a reported sensitivity of 90% to 96% [13,55,61]. HRCT alone is sufficient if only 1 osseous defect is identified and corresponds with the clinical symptoms [12]. HRCT may also be the only study required in patients with iatrogenic CSF leaks for preoperative planning, because the surgical site of leak is known [12]. There is no relevant literature to support the use of contrast-enhanced CT or combined pre- and postcontrast CT in the evaluation of CSF leak. CTA Head There is no relevant literature to support the use of CTA head in the evaluation of sinonasal CSF leak. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT in the evaluation of sinonasal CSF leak. MRA Head There is no relevant literature to support the use of MRA head in the evaluation of sinonasal CSF leak.


Sinonasal Disease

Sinonasal Disease. MRI Head MRI with the inclusion of heavily T2-weighted images is often referred to as an MR cisternogram and is considered the second choice of study and should be done only in conjunction with HRCT [12,55,61]. The heavily T2-weighted sequence covering the roof of the sinonasal cavity in the coronal plane can be included in either an MRI head examination or an MRI orbits, face, and neck examination. A 3-D isotropic heavily T2-weighted sequence should be obtained to provide submillimeter high spatial and contrast resolution and allow for reformats in multiple planes. The site of the CSF leak can be demonstrated on MRI with identification of CSF extending from the subarachnoid space into the sinonasal space through an osseous defect seen on a concurrent or prior CT examination, with or without an associated cephalocele. Sensitivity of 56% to 94% and specificity of 57% to 100% have been reported Sinonasal Disease for the identification of the site of the CSF leak [12-14,55,58,61,63]. Given its superior soft-tissue contrast, MRI can also identify the contents of a cephalocele if present. MRI without IV contrast with inclusion of heavily T2-weighted images is typically sufficient for the evaluation of CSF leak. However, MRI without and with IV contrast may be useful for identifying dural enhancement and distinguishing a meningoceles from sinus secretions [11]. MRI Orbits, Face, and Neck MRI with the inclusion of heavily T2-weighted images is often referred to as an MR cisternogram and may be considered the second choice of study and should be done only in conjunction with HRCT [12,55,61]. The heavily T2-weighted sequence covering the roof of the sinonasal cavity in the coronal plane can be included in either an MRI head examination or an MRI orbits, face, and neck examination. A 3-D isotropic heavily T2-weighted sequence should be obtained to provide submillimeter high spatial and contrast resolution and to allow for reformats in multiple planes.


Sinonasal Disease

Sinonasal Disease. The site of the CSF leak can be demonstrated on MRI with identification of CSF extending from the subarachnoid space into the sinonasal space with or without an associated cephalocele. Sensitivity of 56% to 94% and specificity of 57% to 100% have been reported for the identification of the site of the CSF leak [12- 14,55,58,61,63]. Given its superior soft-tissue contrast, MRI can also identify the contents of a cephalocele if present. MRI without IV contrast with inclusion of heavily T2-weighted images is typically sufficient for the evaluation of a CSF leak. However, MRI without and with IV contrast may be useful for identifying dural enhancement and distinguishing a meningoceles from sinus secretions [11]. Contrast-enhanced MR cisternogram is performed by spinal injection of intrathecal gadolinium, with thin-section T1-weighted images obtained before and after contrast injection. The postinjection images can be obtained immediately after contrast administration or at delayed intervals up to 24 hours after contrast administration. This technique allows for detection of both high-flow and slow-flow leaks and allows for simultaneous evaluation of cephaloceles that may be present. Sensitivity up to 100% has been reported for high-flow leaks and 60% to 70% for slow-flow leaks [12,65]. Studies have demonstrated contrast-enhanced MR cisternogram to have a higher sensitivity of 80% when compared with 33% to 72% of CT cisternogram [13,60]. Intrathecal administration of gadolinium contrast is not currently approved by the US Food and Drug Administration and requires off-label use consent [12]. Radiography Paranasal Sinuses There is no relevant literature to support the use of radiography in the evaluation of a sinonasal CSF leak. SPECT or SPECT/CT Paranasal Sinuses Three studies evaluating the efficacy of SPECT cisternography after the intrathecal injection of radiotracer reported a sensitivity of 94% with SPECT planar imaging and 94% to 100% for SPECT/CT fusion imaging for localization [13,66].


Staging of Colorectal Cancer

Staging of Colorectal Cancer.  In patients with locally advanced rectal cancer (LARC), established risk factors for poorer outcomes include circumferential resection margin involvement, extramural depth of spread >5 mm, extramural vascular invasion (EMVI), mucinous phenotype, and poor response to chemoradiotherapy (CRT) [9,10]. Multiple studies have demonstrated relatively poor compliance with adjuvant (postoperative) chemotherapy compared with neoadjuvant treatment, with decreased survival in the adjuvant (versus neoadjuvant) cohort [11]. Prospective studies have demonstrated that preoperative or neoadjuvant radiation with or without sensitizing chemotherapy reduced local recurrence risk and may increase the proportion of patients who benefit from a sphincter-saving procedure. There is an ongoing effort to assess for complete response to neoadjuvant therapy in an effort to determine which patients could potentially benefit from an organ-preservation approach without total mesorectal excision or lateral nodal dissection. aOregon Health and Science University, Portland, Oregon. bEmory University, Atlanta, Georgia. cPanel Chair, University of Wisconsin Hospital & Clinics, Madison, Wisconsin. dPanel Vice-Chair, University of California San Diego, San Diego, California. eUniversity of Texas Health Science Center at Houston and McGovern Medical School, Houston, Texas; American Gastroenterological Association. fBoston University Medical Center, Boston, Massachusetts. gH. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida. hPRiSMA Proctology Surgical Medicine & Associates, Houston, Texas; American College of Surgeons. iVirginia Tech Carilion School of Medicine, Roanoke, Virginia. jMassachusetts General Hospital, Boston, Massachusetts. kCleveland Clinic, Cleveland, Ohio. lSutter Medical Group, Sacramento, California. mDuke University Medical Center, Durham, North Carolina. nUniversity of Alabama at Birmingham, Birmingham, Alabama. oUniversity of California San Diego, San Diego, California.


Staging of Colorectal Cancer

Staging of Colorectal Cancer. pUniversity of California San Francisco, San Francisco, California. qEmory University, Atlanta, Georgia, Primary care physician. rSpecialty Chair, Virginia Commonwealth University Medical Center, Richmond, Virginia. 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 Staging of Colorectal Cancer Colon Cancer The local treatment of colon cancer relies primarily on the section of involved colon (right versus left hemicolectomy), with removal of the associated mesentery and regional nodes. Use of selective adjuvant chemotherapy is dictated by lymph node positivity and extramural lymphovascular invasion on pathologic specimen. The role of preoperative imaging to predict T stage and N stage is an area of ongoing investigation, given that neoadjuvant therapy has not yet been shown to significantly improve survival over surgery alone (with postoperative adjuvant treatment) and the standard surgical approach is radical resection. Current ongoing trials including the large randomized controlled FOxTROT trial suggest that neoadjuvant treatment can preoperatively downstage colorectal cancer with better tolerated and more complete administration of chemotherapy before surgery rather than postoperative [15]. However, preoperative imaging of colon cancer appears to be of most benefit in identifying distant metastases, regardless of its ability to predict T stage and N stage. Given the limited role of locoregional staging, the imaging variant discussion for colon cancer will be limited to evaluation of distant metastases only.


Staging of Colorectal Cancer

Staging of Colorectal Cancer. Special Imaging Considerations In rectal tumors, because of the need for high-resolution anatomic detail in determining local tumor extension, the local staging of the tumor is often considered separately from the evaluation of distant metastatic disease, resulting in the need for a combination of modalities to fully stage the patient. In contrast, locoregional staging by imaging is not an issue for colon (nonrectal) cancers, and thus only the evaluation of distant metastatic disease is required. OR Discussion of Procedures by Variant Variant 1: Rectal cancer. Locoregional staging. Initial imaging. In this clinical scenario, a patient has been recently diagnosed with rectal cancer and presents for evaluation of local regional extent of the rectal cancer to determine if the person would benefit from neoadjuvant therapy before possible surgical resection. This variant excludes (nonrectal) colon cancers. For lymph node involvement, CT remains relatively nonspecific for N-stage determination. There is little agreement on the critical cut-off diameter to determine if lymph nodes are involved in the disease process. One study suggests 4.5 mm; however, nodal size is not seen as a predictor of nodal status at surgery [8,23]. Because detection of nodes involved with tumor remains a difficult problem, if a colonic resection is planned, local node groups should be encompassed in a properly performed cancer operation. Accuracies for CT detection of lymph node stage range from 56% to 84% [19,20,24-26]. Locoregional staging is not routinely performed for colon cancer; however, CT is Staging of Colorectal Cancer still useful in the initial evaluation of all patients scheduled for colorectal carcinoma surgery because of its ability to obtain a rapid global evaluation and demonstrate potential complications of the tumor (eg, perforation, obstruction) that may not be clinically apparent [18].


Staging of Colorectal Cancer

Staging of Colorectal Cancer. CT Colonography Virtual colonoscopy (or CT colonography) has proven to be a valid tool in identifying both primary and synchronous colonic lesions. Limited information is available regarding the performance of CT colonography for rectal cancer staging. In a study of 45 patients with low rectal adenocarcinomas, CT colonography with multiplanar reformation demonstrated 89% accuracy for T stage [27]. FDG-PET/CT Skull Base to Mid-Thigh Limited recent information is available regarding the performance of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT for local rectal cancer staging. In a study of 59 patients with rectal cancer, conventional FDG- PET/CT was found to be 73.5% accurate for T stage and to have a 64.3% sensitivity and 96.7% specificity for N stage [28]. In an evaluation of 44 pathologic and 19 control lymph nodes, the standardized uptake value (SUV)max and SUVmean were significantly higher in pathological lymph nodes than in control lymph nodes [29]. When used as a preoperative tool in advanced tumors, MRI has shown high diagnostic accuracy for both initial staging to determine surgical plan and determining resectability following neoadjuvant treatment [39-43]. Studies have shown MRI sensitivities ranging from 94% to 100% and specificities from 85% to 88% in assessment of the circumferential resection margin [44,45]. Hence, MRI is valuable in predicting complete resection with negative margins. In a multicenter cohort trial evaluating the use of high-resolution MRI with a phased-array coil in determining resectability, a total of 228 patients underwent curative-intent treatment based on the MRI characterization of tumor extent, with 95.6% of patients achieving margin-negative results [40]. High-risk MRI features (EMVI, extramural tumor depth >5 mm, T4 stage, involved circumferential resection margin) may correlate with a higher risk for distant metastases [46,47].


Staging of Colorectal Cancer

Staging of Colorectal Cancer. In addition to initial staging prognostic features, MRI response to neoadjuvant treatment has been shown to be an indicator of long-term outcomes, including recurrence and survival [48-51]. Reduced field of view diffusion-weighted images (DWI) may demonstrate better image quality than full field of view DWIs [52]. For lymph node involvement, the differentiation of benign from metastatic locoregional nodes remains challenging. MRI is sensitive for detecting enlarged lymph nodes but remains nonspecific for differentiating benign from malignant nodes with accuracies ranging from 59% to 83% [32,36,53,54]. However, studies have shown high negative predictive value in the setting of node-negative determination by MRI, with negative predictive value ranging from 78% to 87% [32,36,53,54]. In a study of 60 patients with rectal cancer, 68.3% of patients with nodal metastasis were correctly identified using a size threshold of 7.2 mm, and accuracy was not improved by morphologic criteria [55]. However, in a study of 52 patients with rectal cancer, prediction of N stage was improved Staging of Colorectal Cancer by considering dimension, morphology, and signal characteristics [56]. Standardized reporting systems and templates have been shown to result in more complete MRI reports [57]. US Pelvis Transrectal TRUS has been considered the reference standard for T-stage evaluation of rectal carcinoma with rich historical evidence to support its use. TRUS is able to differentiate the layers of the rectal wall and provides high accuracy in detecting and characterizing tumors within the superficial layers of the rectal wall. Reported accuracies range between 80% and 97% for T-stage determination [58]. The T-stage accuracy for TRUS (84.6%) is far superior to that of CT (70.5%) [23].


Staging of Colorectal Cancer

Staging of Colorectal Cancer. Evaluation of the extent of the tumor infiltration into the mesorectum (differentiating minimal from advanced T3 tumors and minimal T3 from T2 tumors) is of clinical interest in determining the need for neoadjuvant treatment but remains a challenge for TRUS [59,60]. Although TRUS performs better than MRI for T1 tumors, similar for T2 and T3, it may be less accurate in characterizing locally advanced T4 tumors with a tendency to understage [36]. The use of TRUS in assigning patients to transanal endoscopic microsurgery versus traditional surgery remains controversial. Despite some authors reporting good accuracy for some T stages, a retrospective evaluation of the use of TRUS in patients selected to undergo transanal endoscopic microsurgery for presumed early-stage disease showed disappointing results with inaccurate staging seen in 44.8% of the 165 patients who underwent TRUS preoperatively (32.7% were understaged and 12.1% were overstaged) [61]. In a 2019 study of 500 patients, neither TRUS or MRI distinguished between T1 and T2 disease [62]. A significant limitation of TRUS is the limited field of view that compromises assessment of the relationship of the tumor, mesorectal tumor implants, tumor invasion in extramural vessels, and malignant nodes to the mesorectal fascia. MRI may better evaluate these findings because it offers a larger field of view. TRUS is also limited in its assessment of high rectal tumors. CT Abdomen and Pelvis Much of the literature on CT restaging was generated more than 5 years ago, demonstrating low accuracy for T- stage re-evaluation or assessment of complete response. CT may remain helpful in limited situations to assess for resection margin, overall decrease in tumor, or interval change in node size, and may be of benefit to assess for overall tumor susceptibility to CRT, or in rare cases to detect distant metastatic disease that has developed during the course of neoadjuvant CRT.


Staging of Colorectal Cancer

Staging of Colorectal Cancer. In early studies, accuracy of CT in predicting pathological T stage after radiotherapy was low (37%) but more accurate in the identification of involved circumferential resection margin (71%) [67]. Other studies demonstrated higher accuracy of T stage, up to 61% and CT correlation with pathologic tumor regression, with frequent overstaging due to residual fibrotic change that could not be distinguished from tumor on CT [68]. Nodal involvement was difficult to assess by CT, although change in nodal size could be appreciated, with one early study demonstrating a sensitivity of 56% and a specificity of 74% for nodal involvement [69]. Staging of Colorectal Cancer More recent studies have supported these earlier conclusions, noting that CT restaging was able to document overall response versus nonresponse to neoadjuvant CRT with limited ability to predict pathologic T and N stage at surgical resection; for example, a study of 270 patients receiving CT, MRI, and US restaging revealed 45% accuracy for CT in predicting specific pT stage and 66% accuracy for pN stage [70]. Two surgical cohorts concluded that local restaging CT prompted 0% to 4% change in surgical management of LARC postneoadjuvant CRT and was mostly helpful in the setting of metastatic disease [71,72]. For lymph node involvement, like all modalities that rely primarily on size as determinant of involvement (eg, TRUS and MRI), CT remains relatively nonspecific for N-stage determination. There is little agreement on the critical cut-off diameter to determine if lymph nodes are involved in the disease process before or after neoadjuvant treatment. Nodal size is not seen as a predictor of nodal status at surgery [8,23]. Accuracies for CT detection of lymph node stage range from 56% to 84% [19,20,24-26]. CT Colonography There is no relevant literature regarding the use of CT colonography in the restaging evaluation rectal cancer postneoadjuvant CRT.


Staging of Colorectal Cancer

Staging of Colorectal Cancer. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT has traditionally been used in initial staging of rectal cancer to further evaluate equivocal findings on CT/MRI, to definitively exclude extrahepatic metastatic disease before surgical resection/liver directed therapy, and to identify occult disease in patients with rising carcinoembryonic antigen [73,74]. It is widely considered a specific but not sensitive examination for evaluating distant rather than local disease [75]. A meta-analysis of a combined 1,262 patients with LARC in 19 studies assessed the accuracy of both local tumor restaging as well as regional nodal restaging as determined by restaging MRI compared to surgical pathology of the Circumferential resection margin (involvement or close approximation of the tumor to the mesorectal fascia) assessment may be slightly less predictive at post-CRT MRI compared with pretreatment MRI, again likely due to overstaging by post-CRT imaging [89]. Tumor height on pre- and post-CRT MRI has shown excellent correlation with endoscopic findings, however, and sphincter involvement/distance, with IV contrast MRI, is more helpful in defining the relationship to the sphincter [90,91]. Additional studies confirming that N+ patients had significantly larger nodes than N0 patients both pre- and post- CRT used size cutoff for post-CRT ypN-stage prediction of <2.5 mm and >5mm at MRI [97-99]. Conversely, with luminal tumor apparent complete response, lymph nodes over 7 mm to 8 mm have been more strongly correlated with locoregional node positive (N+) [100,101]. MRI has demonstrated 75% sensitivity and 71% specificity in determining node positive disease [93]. More recently, change in nodal size or DWI signal on restaging MRI has shown more promise in assessment of nodal disease. Lack of a lymph node signal on DWI high b value 1,000 was associated with a sensitivity of 100% and a specificity of 14% [102]; the positive predictive value was 24%, and the negative predictive value was 100%.


Staging of Colorectal Cancer

Staging of Colorectal Cancer. Although the absence of nodes at DWI is not a frequent finding, it appears to be a reliable predictor of yN0 status after CRT and may support the decision to consider organ-preservation treatment. Decreased lymph node size posttreatment is significantly associated with disease-free survival [103]. US Pelvis Transrectal A significant limitation of TRUS is the limited field of view that compromises assessment of relationship of the tumor, mesorectal tumor implants, tumor invasion in extramural vessels, and malignant nodes to the mesorectal fascia. In addition, TRUS is limited in its assessment of high rectal tumors and can only be used in nonstenotic patients. Local tumor staging in a direct comparison of TRUS to MRI in 34 patients, TRUS was accurate in tumor restaging after neoadjuvant CRT in 60% to 62% and high-resolution MRI in 68% [104,105], with a meta-analysis Staging of Colorectal Cancer demonstrating lower diagnostic accuracy than MRI post-CRT, and a statistically significant decline in T-stage accuracy compared with pre-CRT [106]. Sensitivity for complete response on TRUS is as low as 25% with a specificity of 94% [107]. Contrast-enhanced TRUS plus elastography was shown in one study to improve post-CRT local staging to 85% [108]. Detection of lymph node involvement with TRUS is limited to mesorectal nodes in the immediate vicinity of the tumor, which limits sensitivity. The sensitivity pretreatment ranges from 45% to 74% [63,64], and overall accuracy ranges from 62% to 83% [22], and this appears to be similar and even more variable posttreatment [105]. Post-CRT TRUS presents the same limitations of distance from the tumor as at baseline [104]. Variant 3: Colorectal cancer. Staging for distant metastases. Initial imaging. In this clinical scenario, a patient has been recently diagnosed with colon or rectal cancer and presents for evaluation of metastatic disease in the chest, abdomen, and pelvis.


Staging of Colorectal Cancer

Staging of Colorectal Cancer. CT Chest, Abdomen, and Pelvis Most studies show comparable or improved sensitivity for detection of colorectal liver metastases with IV conventional extracellular gadolinium agent-enhanced MRI compared with CT [110,111]. Abdominal/pelvic CT with IV contrast has a high negative predictive value of 90% [112]. Detection of possible lung metastases is also an important part of the initial imaging evaluation of patients with colorectal carcinoma. The National Comprehensive Cancer Network recommends that patients with newly diagnosed colorectal cancer undergo staging chest CT, because staging chest CT has been shown to detect more lung metastases than chest radiography [119]. In a series of 74 patients with newly diagnosed rectal cancer who underwent both chest CT and chest radiography, 37% of patients with a normal chest radiograph had a lesion visible only on the chest CT, and 17% of these patients were found to have at least one pulmonary metastasis [119]. Among patients with potentially resectable liver metastases and a negative initial chest PET, additional imaging with a chest CT revealed pulmonary metastases in 5% of patients [120]. A potential pitfall of chest CT is the detection of small indeterminate pulmonary nodules that are not metastases [121]. In another study, approximately one-fourth of the indeterminate lesions on preoperative CT ultimately developed into metastases and 1 in 10 into other lung malignancies [122]. Chest CT examinations performed to evaluate for pulmonary metastases were typically performed with IV contrast material [121,123,124]. FDG-PET/CT Skull Base to Mid-Thigh Although there is some evidence to support the use of PET/CT in the local staging of patients with rectal carcinoma, the more common clinical application of PET/CT is in identifying nodal and distant metastases [125-127].


Staging of Colorectal Cancer

Staging of Colorectal Cancer. PET/CT is useful for determining overall stage and identifying patients with metastatic disease (sensitivity of 89% and specificity of 64%); however, the accuracy on a lesion-by-lesion basis is relatively low compared with contrast- enhanced CT and MRI for liver metastases (55% versus 89% in a study comparing PET/CT to MDCT) [128,129]. PET/CT may help to exclude other sites of disease beyond the liver or, in complex cases, to improve staging accuracy in which it has been shown to result in a change in management in up to 8% to 11% of patients [128,130- 132]. Caution should be exercised, however, as the findings of PET/CT may be nonspecific and could result in a negative impact on patient care in up to 9% of patients [128]. Additionally, PET/CT has further reduced sensitivity Staging of Colorectal Cancer for lesions in the setting of neoadjuvant therapy and should be used in conjunction with IV contrast CT or MRI for presurgical planning of liver metastases [133]. PET/CT may add influence in the positive predictive value of avid lymph nodes because it has a higher specificity than other modalities. The sensitivity of detecting nodal metastases is only 43% with a specificity of 80%, and again size is not a helpful characteristic. Because of limited sensitivity of MRI for lung nodules, a chest CT can be utilized in addition to abdominal MRI for complete staging. The National Comprehensive Cancer Network recommends that patients with newly diagnosed colorectal cancer undergo staging chest CT, because staging chest CT has been shown to detect more lung metastases than chest radiography [119]. In a series of 74 patients with newly diagnosed rectal cancer who underwent both chest CT and chest radiography, 37% of patients with a normal chest radiograph had a lesion visible only on the chest CT, and 17% of these patients were found to have at least one pulmonary metastasis [119].


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension.  Diagnosis of PH remains challenging because of the diverse group of diseases that can cause PH as well as its nonspecific symptoms. Signs and symptoms of PH include dyspnea, fatigue, palpitations, angina, peripheral edema, hepatomegaly, ascites, syncope, and, rarely, unilateral vocal cord paralysis [4,10]. A careful history evaluation is critical to evaluate for risk factors for PH, including family history, history of drugs and toxins associated with PH, collagen vascular disease, human immunodeficiency virus (HIV), portal hypertension, congenital or left heart disease, and venous thromboembolic disease. Clinical evaluation includes pulmonary function tests, arterial blood gases, routine biochemistry, hematology, thyroid function, and serological testing to evaluate for lung disease, liver disease, connective tissue disorders, and HIV, as well as cardiothoracic imaging [10,11]. 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 Suspected Pulmonary Hypertension All elements are essential: 1) timing, 2) reconstructions/reformats, and 3) 3-D renderings. Standard CTs with contrast also include timing issues and reconstructions/reformats. Only in CTA, however, is 3-D rendering a required element. This corresponds to the definitions that the CMS has applied to the Current Procedural Terminology codes. OR Discussion of Procedures by Variant Variant 1: Suspected pulmonary hypertension. Initial imaging. Radiography Chest PH tends to present with nonspecific symptoms; thus, chest radiography is often the first imaging test performed [11].


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension. Multiple historic studies have shown that chest radiography is a useful study in the initial evaluation of PH [13-19]. Miniati et al [20] found that chest radiography has a high sensitivity (96.9%) and specificity (99.1%) for detection of moderate to severe PH. Additionally, chest radiography can show findings of diffuse lung diseases that can be associated with PH, such as interstitial fibrosis and emphysema [10,13]. Although chest radiography does well in detecting the presence/absence of PH in moderate and severe cases of PH, it performs poorly in estimating the PH severity [14]. Additionally, it is known to be insensitive in the detection of mild PH. Thus, a normal chest radiograph does not exclude PH, and further imaging evaluation should be pursued if there are persistent unexplained symptoms such as dyspnea or risk factors for PH [13,15,17,20,21]. Findings of PH on chest radiography include enlargement of the central pulmonary arteries, with or without rapid tapering (pruning), and right heart chamber enlargement [10,17,19,21]. A study by Schmidt et al [17] found that the main PA (MPA) was enlarged (>35 mm from midline to left lateral border of the PA on posterior anterior radiograph) 96% of the time in PH. A measurement of the right descending PA >15 mm in women (>16 mm in men) at the hilum on a posterior anterior view has good sensitivity, specificity, and accuracy for PH (93%, 88%, and 92%, respectively) and is considered to be a very useful finding [16-18]. A diameter of the left descending PA >18 mm on the lateral view is also suggestive of PH, but although it has good sensitivity (93%), the specificity (67%) and accuracy (87%) are poorer [16]. Other studies, such as that of Schmidt et al [17], have found poorer sensitivity for the left descending PA measurement. Miniati et al [20] found the most prevalent radiographic findings in patients with PH were enlarged MPA (97%), enlarged right ventricle (95%), and enlarged right descending PA (93%).


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension. US Echocardiography Transthoracic Resting Transthoracic Doppler echocardiography is a noninvasive test that is a useful part of the initial evaluation of suspected PH [22]. A recent meta-analysis by Ni et al [23] showed that, overall, it has good sensitivity and fair specificity (85% and 74%, respectively) for detecting moderate to severe PH. However, it does not perform as well in detecting mild PH, particularly cases of PH secondary to lung diseases. Transthoracic Doppler echocardiography uses continuous wave Doppler to measure the peak tricuspid regurgitation velocity, which is used in combination with various echocardiographic signs suggestive of PH to assign a low, intermediate, or high echocardiographic probability of PH [24-26]. Echocardiographic signs suggestive of PH fall into 3 categories: right ventricular (RV) findings, PA findings, and inferior vena cava (IVC)/right atrial (RA) findings. RV findings include RV/left ventricular (LV) basal diameter ratio >1 and flattening of the interventricular septum. PA findings include PA diameter >25 mm, early diastolic Transthoracic Doppler echocardiography is also useful in the assessment of multiple right heart parameters that are influenced by PH, including RA and RV size, RV systolic function, RV strain, tricuspid annular plane systolic excursion, and biventricular index. A biventricular index (RV end-diastolic area to LV end-diastolic area) >0.93 is associated with an increased risk of death in patients with PH [22,27]. The presence of pericardial effusion as well as valvular morphology and function are also easily assessed by echocardiography. An echocardiographic bubble study using agitated saline can be performed during the examination to assess for intracardiac shunts [11]. Studies have shown that real-time 3-D echocardiography evaluates RV volumes and the ejection fraction more accurately than conventional 2-D echocardiography [28].


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension. In addition, pressure gradient-volume diagrams derived from 3-D echocardiography data can be used to reliably estimate RV stroke work in patients with PH [29]. Populations including those with a known genetic mutation associated with PAH, first degree relative with PAH, scleroderma spectrum, congenital heart disease, and portal hypertension before liver transplant are at high risk of developing PAH and may benefit from screening with echocardiography [30]. Patients with a high echocardiographic probability for PH have poorer postsurgical outcomes; thus, PH echocardiographic probability can also be used to risk stratify patients with risk factors for PH before a procedure/surgery [27,31]. As mentioned above, transthoracic Doppler echocardiography will not reliably detect mild, asymptomatic PH. Further evaluation with additional noninvasive examinations including CT and MRI may be obtained if there is persistent, high clinical suspicion for PH. RHC is also useful for further evaluation [10,24]. V/Q Scan Lung There are no data to suggest ventilation-perfusion (V/Q) scintigraphy as an initial test in the workup of suspected PH. However, current guidelines recommend V/Q scintigraphy of the lungs in all patients with unexplained PH to assess for CTEPH [24]. Identification of CTEPH is important because it allows for potentially curative surgical therapy [33]. V/Q scintigraphy typically shows mismatched wedge-shaped, segmental defects in the setting of CTEPH that can normalize after surgical treatment [34]. The high sensitivity and specificity of V/Q scintigraphy is useful for CTEPH detection [34]. A recent study by Mehari et al [35] comparing V/Q scintigraphy and multidetector CT pulmonary angiography (CTPA) for CTEPH detection found that V/Q scintigraphy had excellent sensitivity (90%) and good specificity (75%), whereas CTPA suffered from poor sensitivity (37%), although it had excellent specificity (100%).


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension. This is comparable to a prior study by Tunariu et al [36], which found that V/Q scintigraphy was more sensitive than multidetector CTPA in detecting chronic thromboembolic pulmonary disease amenable to surgery, with V/Q scans demonstrating a sensitivity of 96% to 97% and a specificity of 90% to 95% compared with a sensitivity of 51% and specificity of 99% for multidetector CTPA. However, a study that compared V/Q scanning versus CTPA by He et al [37] showed both techniques had good sensitivity, specificity, and accuracy at a center with significant CTEPH experience (100% versus 92%, 94% versus 95%, and 97% versus 94%, respectively). Compared with planar V/Q scanning, V/Q single-photon emission CT improves sensitivity and specificity, resulting in an accuracy of 94% [38]. The slightly lower specificity of V/Q scintigraphy relative to multidetector CTPA is secondary in patients with idiopathic Suspected Pulmonary Hypertension PAH (IPAH) in whom abnormal V/Q scans can also be demonstrated whom can also demonstrate abnormal V/Q scans [33,38]. Although V/Q scintigraphy has excellent sensitivity for CTEPH, its greatest power lies with its negative predictive value. A normal or low-probability scan essentially excludes the diagnosis of CTEPH, although the V/Q scan may be normal in other causes of PH [10,24,33]. CT Chest CT chest is another noninvasive technique that can assess for PH. CT chest can be performed with or without intravenous (IV) contrast but is ideally performed with IV contrast to adequately visualize the pulmonary vasculature. CT chest without IV contrast is not a first-line test for suspected PH but may be useful to help look for etiologies of PH in patients who already hold a diagnosis of PH. There are no data support obtaining a CT chest with and without IV contrast in the setting of suspected PH.


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension. In addition to demonstrating findings suggestive of PH, chest CT can also characterize various pulmonary etiologies that cause PH, including IPAH, pulmonary capillary hemangiomatosis (PCH), pulmonary veno-occlusive disease (PVOD), and many diffuse lung diseases. IPAH is characterized by plexiform lesions, which are networks of capillary-like channels in the wall of a dilated muscular PA that appear as ground glass centrilobular nodules. IPAH findings on CT include dilated central pulmonary arteries, centrilobular ground glass nodules associated with enlarged tortuous centrilobular arterioles, and pericardial effusion [21,46]. PCH, a diffuse proliferation of capillaries in the pulmonary interstitium, and PVOD, a disease of pulmonary venous hypertension secondary to pulmonary vein intimal fibrosis and subsequent venous occlusion, are rare diseases whose diagnosis can be suggested by findings on CT. On CT, PCH will have enlarged pulmonary arteries, centrilobular ground glass nodules, and interlobular septal thickening. PVOD presents on CT with enlarged pulmonary arteries, lymphadenopathy, pleural effusion, and interlobular septal thickening in the setting of a normal size left atrium. Surgical biopsy is necessary to confirm the diagnosis of PCH and PVOD [46-48]. Suspected Pulmonary Hypertension uncommon finding in PH, has also been reported at CTA [52,53]. As with chest CT, evaluation with RHC remains necessary to confirm PH suspected on CTPA before initiating therapy [24]. MRI Heart Function and Morphology MRI can also noninvasively assess the MPA and right ventricle for PH with good sensitivity and specificity (92% and 80%, respectively) and is useful for RV morphology and function assessment.


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension. RV functional abnormalities secondary to PH-related cardiac remodeling include RV hypokinesis, leftward bowing and/or paradoxical movement of the interventricular septum, RV dysfunction (increased end-diastolic volume, reduced ejection fraction, reduced cardiac index, reduced stroke volume), and pulmonary and tricuspid insufficiency [59-62]. RV mass and LV mass can also be accurately determined, which can then be used to calculate a ventricular mass index (RV mass/LV mass), with a ratio >0.6 being abnormal [61,63,64]. Cardiac MRI shows many of the morphologic changes of PH that are also depicted by chest CT and CTPA: PA enlargement, MPA to adjacent ascending aorta ratio > 1, RV enlargement and hypertrophy, straightening of the interventricular septum, and pericardial thickening and effusion [61,65,66]. Measured parameters of RV ejection fraction, RV end diastolic volume, and RV-PA coupling metrics measured on cardiac MR have been shown to be important prognostic indicators of PH [59,65]. Additional characteristic findings of PH on cardiac MRI include findings on late gadolinium enhancement, T1 mapping, and phase-contrast sequences. Enhancement of the RV insertion points on late gadolinium enhancement imaging is commonly present in individuals with PH and is compatible with fibrosis related to RV stress [60,62,63,67]. T1 mapping will also show abnormally prolonged values at the RV insertion points in PH [68,69]. Cardiac MRI phase-contrast imaging techniques can measure average blood flow velocity of the MPA, which correlates with mPAP. Patients with PH have sluggish PA flow as demonstrated by prolonged acceleration times on phase-contrast imaging. Severity of tricuspid regurgitation can be accurately quantified with 2-D phase-contrast imaging and used to estimate MPA pressure [65,70,71].


Suspected Pulmonary Hypertension

Suspected Pulmonary Hypertension. More recently, 4-D flow has been used to assess the MPA and detect the hemodynamic alterations that occur with PH: decreased wall shear stress, increased tricuspid regurgitation velocity, and abnormal vortex blood flow pattern within the MPA that is associated with early-onset systolic retrograde flow [65,72-74]. MRA Chest Pulmonary MR angiography (MRA) shows morphologic changes of PH that are also depicted by MRI heart and CT/CTPA: PA enlargement, MPA to adjacent ascending aorta ratio >1, RV enlargement and hypertrophy, straightening of the interventricular septum, and pericardial thickening and effusion [61,65,66]. MRA has lower sensitivity for the detection of acute and chronic pulmonary embolism compared with CTPA [61]. There are no data to support the use of MRA chest alone as a first-line test for suspected PH; however, the combination of MRA Catheterization Right Heart RHC is an invasive procedure that defines cardiopulmonary hemodynamics and is performed after all noninvasive examinations have been completed to confirm the diagnosis of PH before initiating treatment per current guidelines [24]. RHC directly measures the PAP to confirm the diagnosis of PH as well as the PAWP and cardiac function (thermodilution or Fick method), which are both necessary to determine PVR. The mean PAP, PAWP, and PVR values obtained from RHC are used to classify PH into precapillary PH, isolated postcapillary pH, or combined pre- and postcapillary PH [78-80]. Vasoreactivity testing of the pulmonary circulation may also be performed at the time of RHC in selected patients with IPAH, heritable PAH, and drug-induced PAH to determine candidacy for calcium channel blocker treatment [79]. RHC has morbidity and mortality rates of 1.1% and 0.055%, respectively [81]. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list.