Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma.  Introduction/Background Hand injuries account for approximately 20% of emergency department visits [1]. According to the National Hospital Ambulatory Medical Care Survey, 1.5% of all emergency department visits involve hand and wrist fractures. Distal radius fractures are especially common, accounting for up to 18% of fractures in the elderly [2,3]. Because of increasing rates of osteoporosis, the incidence of distal radius fractures has been increasing [4]. Although most distal radius fractures in elderly patients are managed nonoperatively, the use of internal fixation is increasing. Internal fixation has a much higher cost than nonoperative treatment as well as increased rates of hospitalization [5]. For most patients with trauma to the hand and wrist, conventional radiographs provide sufficient diagnostic information to guide the treating physician. However, delayed diagnosis is common because distal radius and scaphoid fractures may be radiographically occult [6]. When initial radiographs are normal but there is high clinical suspicion for fracture, further imaging with additional radiographic projections, CT, or MRI is appropriate. If associated soft-tissue injury is clinically suspected, CT, CT arthrography, MRI, MR arthrography, or ultrasound (US) may be indicated [7-10]. Successful treatment of distal radius fractures requires restoration of radial length, inclination, and tilt, as well as the realignment of the articular fracture fragments [9,11]. The presence of a coronally oriented fracture line, die- punch depression, or more than three articular fracture fragments are common indications for operative reduction [8]. Operative fixation resulting in <2 mm of residual articular surface step-off is usually considered necessary to avoid long-term complications, such as osteoarthritis [9,12]. A standard 3-view radiographic examination of the hand shows most fractures and dislocations of the metacarpals and phalanges [13].


Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma. For phalangeal injuries, some centers include a PA examination of the entire hand, whereas others limit the examination to the injured finger. An internally rotated oblique projection, in addition to the standard externally rotated oblique, increases diagnostic yield for phalangeal fractures [15]. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: publications@acr.org Acute Hand and Wrist Trauma Most fractures of the thumb are visible on a 2-view radiographic examination, although there is a slight increase in diagnostic yield with the addition of an oblique projection [13], which can be obtained along with a PA examination of the whole hand. CT Area of Interest In patients with intra-articular fractures seen on radiography, CT shows articular fracture fragment displacement, depression, and comminution more accurately than conventional radiographs [7,9,10]. CT measurements of articular surface gap and step-off are more reproducible than radiographs [7]. The addition of 3-D surface- rendered reconstructions to the standard 2-D CT images has been shown to change operative management in up to 48% of intra-articular distal radius fractures [8]. There is no evidence to support the use of CT with intravenous (IV) contrast in the setting of acute hand and wrist trauma. MRI Area of Interest MRI is not indicated initially in this clinical setting. US Area of Interest US is not indicated initially in this clinical setting. Bone Scan Area of Interest Bone scan is not indicated in this clinical setting. Variant 2: Suspect acute hand or wrist trauma. Initial radiographs negative or equivocal. Next imaging study.


Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma. Radiography Area of Interest In patients with clinical suspicion of hand or wrist fracture and negative radiographs, one option is to place the patient in a short arm cast and repeat the radiographs at 10 to 14 days [13]. The downside of this option is that it results in delay of diagnosis, which may lead to functional impairment. CT Area of Interest When the initial radiographs are equivocal, CT without IV contrast is commonly used to exclude or confirm suspected wrist fractures [18]. CT shows intra-articular extension of distal radius fractures more frequently than radiography. Three-dimensional reconstructions can be particularly helpful in preoperative planning for complex articular injuries [7,8]. CT should be used to exclude an occult fracture of the upper extremity. Unlike MRI, CT cannot evaluate for concomitant ligamentous injuries [19-21]. CT is useful in diagnosing injuries that are difficult to recognize on radiographs, such as carpometacarpal joint fracture dislocations. For metacarpal and digital fractures, CT is usually not indicated during acute injury [22]. There is no evidence to support the use of CT with IV contrast in the setting of acute hand and wrist trauma. MRI Area of Interest When initial radiographs are normal but there is high clinical suspicion for fracture, MRI without IV contrast can detect fractures of the distal radius and carpal bones [12,23-25]. One study of patients in which the radiographic findings did not explain the clinical symptoms reported that the MRI led to a change in diagnosis in 55% of patients and a change in patient management in 66% [12]. However, another study of patients with acutely injured wrists reported that the MRI did not predict the need for treatment better than the combination of physical examination and radiography [23]. More importantly, there was no difference in outcomes with MRI compared with radiography [24].


Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma. Acute Hand and Wrist Trauma Like CT, MRI shows intra-articular extension of distal radius fractures more frequently than radiography. Unlike CT, MRI shows concomitant ligament injuries, including tears of the scapholunate ligament, which may affect surgical treatment [26,27]. Despite these advantages, MRI performed immediately at the time of injury has little added value for determining which patients go on to surgery [23]. MRI is especially useful in evaluating hand soft-tissues injuries, including the collateral ligaments, volar plates, tendons, and pulleys. For metacarpal and digital fractures, MRI is usually not indicated during acute injury [22]. There is no evidence to support the use of MRI with IV contrast in the setting of acute hand and wrist trauma. US Area of Interest US may have a limited utility for evaluating bone injuries. Christiansen et al [28] reported 47% sensitivity and 61% specificity of US for the detection of scaphoid fractures. They concluded that US is not suitable for the early diagnosis of scaphoid fracture. In contrast, Hauger et al [29] reported that using cortical disruption as a diagnostic criterion on US is an accurate sign for detecting occult fractures of the scaphoid waist. Further study of US for the diagnosis of occult fractures is needed. Bone Scan Area of Interest Bone scan is not indicated in this clinical setting. CT Arthrography Wrist When conventional radiographs do not show carpal malalignment, CT arthrography may be used to diagnose ligamentous tears, causing dynamic instability [32,33]. There is a growing body of literature comparing the diagnostic accuracy of MRI (at 1.5T or 3T), MR arthrography (indirect or direct at 1.5T or 3T), and CT arthrography. Overall, CT arthrography is reported to have the highest sensitivity, specificity, and accuracy. For the detection of scapholunate ligament tear, CT arthrography has sensitivity, specificity, and accuracy of nearly 100%.


Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma. For the detection of lunotriquetral ligament tear, CT arthrography has approximately 100% sensitivity, 80% specificity, and 90% accuracy. Compared with arthroscopy, CT arthrography has 80% to 100% sensitivity for scapholunate and lunotriquetral ligament tears [33-35]. Compared to MR arthrography, CT arthrography detects partial ligament tears more accurately, detects articular cartilage defects more accurately, and has greater interobserver agreement [33]. Both CT arthrography and MR arthrography have a very high accuracy for diagnosing tears of the scapholunate ligament and lunotriquetral ligament; both are more accurate than conventional MRI [36]. The accuracy of CT arthrography for extrinsic ligament injuries is unknown [37]. CT Wrist CT is not indicated in this clinical setting. MRI Wrist When conventional radiographs do not show carpal malalignment, MRI is commonly used to diagnose ligamentous tears. In the clinical setting of dynamic instability, MRI or MR arthrography may be performed. Modern MR techniques using 3T systems, dedicated wrist coils, and 3-D isovolumetric sequences offer fast imaging times with high spatial and contrast resolution [36,38]. In general, 1.5T MRI has moderate sensitivity for the detection of scapholunate ligament tears and poor sensitivity for lunotriquetral ligament tears [35]. A meta-analysis of 11 studies reported sensitivities and specificities of 70% and 90% for detection of scapholunate ligament tears and 31% and 89% for detection of lunotriquetral ligament tears, respectively [39]. Sensitivity of 3T MRI is slightly better than 1.5T for the diagnosis of interosseous ligament tears. Reported sensitivities range from 65% to 89% for scapholunate ligament tears and 60% to 82% for lunotriquetral ligament Acute Hand and Wrist Trauma tears [36,40-42]. Some investigators consider the diagnostic accuracy of 3T MRI and MR arthrography to be comparable [38]. The accuracy of MRI for extrinsic ligament assessment is unknown [37].


Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma. Extensor carpi ulnaris tendinopathy, tenosynovitis, and tendon rupture can be evaluated with MRI or US [43]. However, dynamic instability may be missed on MRI, unless sequences are performed in pronation and supination [44]. MR Arthrography Wrist At 1.5T, MR arthrography has greater sensitivity compared with conventional MRI [45,46]. Both MRI and MR arthrography have poor to moderate sensitivity for partial ligament tears [47,48]. When only complete tears are considered, MRI and MR arthrography may be equivalent [33]. The accuracy of MR arthrography for extrinsic ligament assessment is unknown [37]. For tears of the dorsal band of the scapholunate ligament, US sensitivity varies from 46% to 100% and specificity from 92% to 100% [50-52]. For the dorsal band of the lunotriquetral ligament, US sensitivity ranges from 25% to 50% and specificity from 90% to 100% [52,53]. US visualization of lunotriquetral ligament (particularly the structurally important volar band) is limited [49]. US can show dynamic subluxation of the extensor carpi ulnaris tendon during forced supination [44]. Bone Scan Wrist Bone scan is not indicated in this clinical setting. Variant 4: Initial radiographs showing distal radioulnar joint or carpal malalignment in the absence of fracture. Next imaging study. CT Wrist CT is the modality of choice for evaluating distal radioulnar joint stability [54]. The CT protocol should include imaging of both wrists in maximal pronation, neutral position, and maximal supination. CT examination with coronal, sagittal, and 3-D reformed images help demonstrate the extent of injury and help in treatment planning, particularly in cases of chronic perilunate dislocation [55]. CT Arthrography Wrist Distal radioulnar joint instability and traumatic triangular fibrocartilage injuries can be evaluated with CT arthrography [56,57].


Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma. MRI Wrist Distal radioulnar joint instability and traumatic triangular fibrocartilage injuries are usually associated with fluid in the distal radioulnar joint, which aids in the evaluation of the triangular fibrocartilage components on conventional MRI. MR Arthrography Wrist MR arthrography increases the diagnostic accuracy for proximal lamina (foveal) triangular fibrocartilage tears [56,57]. US Wrist US is not indicated in this clinical setting. Bone Scan Wrist Bone scan is not indicated in this clinical setting. Variant 5: Acute hand fracture on radiographs. Suspect hand tendon or ligament trauma. Next imaging study. CT Hand CT has limited use for the diagnosis of soft-tissue injuries of the hand. Acute Hand and Wrist Trauma MRI Hand MRI is ideal for evaluating tendon injuries and helping with surgical planning [58,59]. MRI is commonly used for the diagnosis of Stener lesions of the thumb [60] and the diagnosis of pulley system injuries [61]. Hergan et al [62] reported a 100% sensitivity and specificity for assessment of thumb ulnar collateral ligament tears. Spaeth et al [63] reported a sensitivity of 100% and specificity of 94% for detection of displaced ulnar collateral ligament tears in 16 cadaveric specimens. US Hand A Stener lesion occurs when the aponeurosis of the adductor pollicis muscle becomes interposed between the ruptured ulnar collateral ligament of the thumb and its site of insertion at the base of the proximal phalanx. This lesion can be identified by absence of ulnar collateral ligament and the presence of a hypoechoic mass proximal to the apex of the metacarpal tubercle [64]. Dynamic examination shows the relationship of the aponeurosis to the retracted ligament stump [65]. US allows for diagnosis of pulley system injuries [66,67]. Bone Scan Hand Bone scan is not indicated in this clinical setting. Variant 6: Initial radiographs showing metacarpophalangeal, proximal interphalangeal, or distal interphalangeal joint malalignment in the absence of fracture.


Acute Hand and Wrist Trauma

Acute Hand and Wrist Trauma. Next imaging study. CT Hand CT has limited use for the diagnosis of soft-tissue injuries of the fingers. MRI Hand MRI is ideal for evaluating tendon injuries and helping with surgical planning [58]. MRI may be used to assess capsule and collateral ligament injuries of the proximal interphalangeal and metacarpophalangeal joints [68]. MRI allows for the assessment of pulley system lesions [66,67]. MRI can accurately depict the pulley system, particularly the A2 and A4 pulleys, with lower sensitivity for A3 and A5 pulleys [70]. Hauger et al [70] reported direct identification of A2 and A4 pulleys in 12 of 12 cases (100%) and direct diagnosis of an abnormal A2 pulley in 100% and A4 pulley in 91% of 33 cases. For volar plate injuries, MRI may be used to diagnose tears that do not involve the underlying bone [71]. This is important because untreated lesions can result in contractures or joint laxity [72]. MRI is especially useful for detection of ulnar collateral ligament and radial collateral ligament injuries. Pfirrmann et al [74] reported a sensitivity of 67% and a specificity of 91% for collateral ligament injuries of the lesser metacarpophalangeal joints. With MR arthrography, sensitivity and specificity increased to 75% and 98%, respectively [74]. US Hand Dynamic US allows direct visualization of subluxation/dislocation of the extensor tendon while the patient flexes the metacarpophalangeal joint [16,75]. US helps evaluate injured flexor tendons and, in cases of completely lacerated tendons, helps identify the location of the proximal tendon stump [76]. Acute Hand and Wrist Trauma US allows for assessment of pulley system injuries [66,67], particularly the A2 and A4 pulleys, with lower sensitivity for A3 and A5 pulleys [70]. Bone Scan Hand Bone scan is not indicated in this clinical setting. Variant 7: Suspect penetrating trauma with a foreign body in the soft tissues in the hand or wrist. Initial radiographs are negative. Next imaging study.


Chylothorax Treatment Planning

Chylothorax Treatment Planning.  Introduction/Background Chyle is primarily formed in the intestines and is composed of proteins, lipids, electrolytes, and lymphocytes. A chylous pleural effusion, or chylothorax, is a highly morbid condition defined by the presence of chyle within the pleural respiratory compromise, immunosuppression, malnutrition, and even death [1-3]. A review of the etiology, diagnosis, and management of chylothorax is presented in addition to an evaluation of relevant imaging studies. Etiology Chylothoraces can be categorized etiologically as traumatic or nontraumatic. Collectively, the incidence of chylothorax is approximately 1 per 6000 admissions [1]. Historically, nontraumatic etiologies accounted for up to 72% of cases. Most recently, the largest study reports that traumatic etiologies account for 54% of cases [1,4-7]. The discrepancy may reflect the growth in thoracic oncologic resections or specific referral patterns. Diagnosis Chylothorax most commonly presents with dyspnea, although chest pain, fever, and fatigue may also occur. Chyle is odorless, alkaline, sterile, and milky in appearance, although the appearance may vary based on the nutritional status of the patient. Increasing fatty intake increases the volume and can change the color of the fluid and has been described for the diagnosis of a chyle leak. The hallmark of chylous effusion is the presence of chylomicrons in the fluid. Objective diagnostic criteria include a pleural fluid triglyceride level >110 mg/dL and a ratio of pleural fluid to serum triglyceride level of >1.0. A ratio of pleural fluid to serum cholesterol level of <1.0 distinguishes chylothorax from cholesterol pleural effusions, which may present similarly [2,3]. Management The diagnosis is confirmed by draining the fluid for studies; this is also palliative. After replacing fluid and protein losses, a decision about conservative versus invasive therapies can be made.


Chylothorax Treatment Planning

Chylothorax Treatment Planning. If the chylothorax reaccumulates, treatment is guided by daily outputs, with higher outputs warranting a more aggressive approach [2,4,8-11]. Conservative measures include management of the underlying disease, thoracentesis, and dietary modifications such as total parenteral nutrition or a nonfat diet to reduce production of chyle and consequently flow through the thoracic duct. Adjunctive therapy may include somatostatin, etilefrine, or nitric oxide, with the underlying etiology determining the efficacy, although the evidence remains scarce. The success of conservative therapy approaches 50% in nonmalignant etiologies but is only minimally beneficial in neoplastic etiologies [2,10,11]. Exact criteria for the implementation of invasive treatment are not well defined, but several authors advocate its use if conservative treatment has not resolved the chylothorax after 2 weeks, in higher-output chylothoraces, and in underlying neoplastic etiologies. Invasive treatments include surgical thoracic duct ligation, pleurodesis, and thoracic duct embolization (TDE) [2,4,8-11]. Less commonly, tunneled drains or pleural shunt procedures are performed, although prolonged drainage is not recommended as a long-term option because of increased risk of complications [12,13]. Although the technical success of direct surgical ligation is high, these debilitated patients 1Principal Author and Panel Vice-Chair (Vascular Imaging), University of Michigan Health System, Ann Arbor, Michigan. 2Research Author, University of Michigan, Ann Arbor, Michigan. 3Panel Chair (Interventional Radiology), Cleveland Clinic Foundation, Cleveland, Ohio. 4Yuma Regional Medical Center, Yuma, Arizona. 5Massachusetts General Hospital, Boston, Massachusetts. 6Beth Israel Deaconess Medical Center, Boston, Massachusetts, Society of Thoracic Surgeons. 7Vanderbilt University Medical Center, Nashville, Tennessee, American College of Chest Physicians. 8University of Nebraska Medical Center, Omaha, Nebraska.


Chylothorax Treatment Planning

Chylothorax Treatment Planning. 9University of California San Diego, San Diego, California. 10University of Texas Southwestern Medical Center, Dallas, Texas. 11Specialty Chair (Interventional Radiology), University of Chicago Hospital, Chicago, Illinois. 12Panel Chair (Vascular Imaging), UT Southwestern Medical Center, Dallas. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: publications@acr.org Chylothorax Treatment Planning are at increased risk for postoperative adhesions, infection, and poor wound healing. Reported postoperative mortality rates for patients who have failed conservative management range from 4.5% to as high as 50% [2,4,9,10]. TDE is a percutaneous alternative to thoracic duct ligation. TDE allows for direct embolization (Type I) or needle disruption of the thoracic duct (Type II). Whereas the former directly treats the focus of injury, the latter is purported to create a controlled leak and inflammatory reaction in the retroperitoneum, which collateralizes and diverts flow from the thoracic duct. Over several successive publications, Cope et al [14,15] defined the technique and reported its feasibility. The initial series of 42 patients by Cope and Kaiser [16] revealed effective percutaneous treatment in >70% of cases. In 109 patients with traumatic thoracic duct leak, Itkin et al [5] reported 90% clinical resolution postembolization and 72% clinical resolution of the chyle leak with thoracic duct disruption. A subsequent report by Nadolski and Itkin [6] reported that TDE for nontraumatic chylous effusions in 34 patients was primarily successful if there was thoracic duct occlusion and extravasation.


Chylothorax Treatment Planning

Chylothorax Treatment Planning. Pamarthi et al [7] reported 85% technical success and 64% clinical success in 105 patients with all-cause chylous leaks. Additional series have yielded similar results. Collectively, TDE has higher clinical success treating traumatic compared with nontraumatic chyle leaks and with TDE compared with thoracic duct disruption [8,9,11,17]. Overall, acute complications associated with TDE are minor and generally self-limited and are estimated at 2% to 6% [5-7]. Long-term complications may be seen in up to 14% of patients and may include leg swelling, abdominal swelling, or chronic diarrhea [18]. Overview of Imaging Modalities Different imaging studies serve different purposes in the evaluation and treatment of chylothorax. Chest radiography Chest radiographs are routine examinations to evaluate dyspnea, particularly in postoperative scenarios and in patients who require intensive care. Radiographs can reliably detect pleural effusions or alternative diagnoses and monitor the position of support lines and tubes [19]. Although there is a high sensitivity for pleural effusions, this technique cannot reliably characterize the type of effusion. Ultrasound Ultrasound (US) is sensitive for the detection of pleural fluid but cannot definitively discriminate between the types of pleural effusion [20]. US is now commonly used to help guide thoracentesis. Similarly, US can be used to facilitate intranodal lymphangiography, which is becoming a more accepted technique. Beyond facilitating these procedures, the role of US is limited with regard to the evaluation and management of chylothorax [21]. Conventional lymphangiography Lymphangiography has historically been used to opacify lymphatic vessels, detect lymph nodes and metastatic lesions, and evaluate lymphatic flow.


Chylothorax Treatment Planning

Chylothorax Treatment Planning. Technological improvements in alternative diagnostic modalities led to an abandonment of this technique for oncologic purposes because it was technically challenging and time intensive, provided less information, and was more invasive. Although proficiency and training in the performance of lymphangiograms decreased, the utility of lymphangiography to demonstrate lymphatic leak became an established indication [8,9,14,22,23]. Traditionally, lymphangiography is performed from a pedal approach with the patient in a supine position. In this technique, a dye such as methylene blue that stains the lymphatics is injected into the web spaces between the toes. After the lymphatic vessel fills with the dye, the tissue overlying the lymphatic vessel is incised vertically, the lymphatic vessel is carefully skeletonized, and a 30-gauge lymphangiography needle is used to access the vessel. After securing the lymphatic access, 6 to 8 mL of ethiodized oil is instilled at a rate of 4 to 10 mL/h. Serial spot radiographs from the foot to the chest are acquired approximately every 10 to 15 minutes to follow the progression of the ethiodized oil as it ascends [22,24-27]. More recently, an interest in nodal lymphangiography has developed [21,28]. In this alternative approach, an inguinal lymph node is targeted with a 25- to 26-gauge spinal needle under US guidance. The needle is positioned between the hilum and cortex of a lymph node. Hand injection of ethiodized oil at a rate of 1 mL per 5 to 7 minutes is then initiated for a total volume of 6 to 10 mL. Serial spot radiographs of the pelvis, abdomen, and thorax are then acquired to follow the progression of ethiodized oil [21,25,28-30]. Intranodal lymphangiography appears to decrease procedure time, is less technically challenging, and decreases the risk of wound infection when compared to pedal lymphangiography [21,28].


Chylothorax Treatment Planning

Chylothorax Treatment Planning. Chylothorax Treatment Planning Lymphangiography is able to define the site of the leak, diagnose alternative lymphatic vessel diseases, and prevent unnecessary procedures. Several authors have documented the therapeutic benefit of lymphangiography to occlude the site of leakage in 37% to 70% of patients without additional procedures [24-30]. Moreover, as detailed earlier, lymphangiography is intrinsic to the performance of TDE and guides the transabdominal access to the cisterna chyli and thoracic duct [14-16]. Magnetic resonance imaging chest and abdomen Visualization of the cisterna chyli, thoracic duct, and tributary lymphatic vessels with magnetic resonance imaging (MRI) was described in healthy volunteers as early as 1999 [34]. Initial MR lymphangiography technique involved unenhanced thin-collimated axial and coronal sequences similar to magnetic resonance cholangiopancreatography. Further refinements of sequences, particularly heavily T2-weighted sequences with and without and fat suppression, combined with 3-D techniques, maximum-intensity projections, and higher magnetic fields, increased the reliability and quality of MR lymphangiography [35-39]. Morphological features of the cisterna chyli and thoracic duct can be noted with identification of these structures in over 90% of preoperative patients, potentially providing valuable information and decreasing their risk of lymphatic leak [40- 43]. The vast majority of studies are performed with unenhanced techniques, although delayed-phase cisterna chyli enhancement has been noted [44]. Respiratory gating and further technical refinements have the potential to better elucidate minor lymphatic vessels and lymphatic vessels in antidependent areas, which may not be seen through conventional lymphangiography. Recent studies are beginning to document the feasibility of using gadolinium- based contrast material injection within groin lymph nodes or in the web spaces between toes.


Chylothorax Treatment Planning

Chylothorax Treatment Planning. Following the contrast material injection, patients are imaged with MRI. High image quality of lymph nodes, central lymphatics, and flow patterns within the lymphatics has been described, but these are preliminary research experiences and are not widely available [45,46]. Computed tomography chest and abdomen Older studies noted that noncontrast computed tomography (CT) visualizes the cisterna chyli in 1.7% of cases and could differentiate this from adjacent anatomy by its low attenuation, continuity with the thoracic duct, and tubular nature [47]. At least some portion of the thoracic duct was visualized in 55% of patients in a different series [48]. Although MRI more reliably visualized more segments of the thoracic duct than CT, the addition of CT increased the number of visualized segments [36]. More recent studies with 1-mm collimation and multiplanar reformation were able to identify the thoracic duct and cisterna chyli in nearly 100% of CT scans with normal anatomy [49]. Older reports using a combination of lymphangiography and CT did not find any additional value of CT in diagnosing the lymphatic injury, although in a more recent series, a combination of CT and unilateral pedal lymphangiography was able to identify the cause and locate the leak in 75% of idiopathic chylothoraces after failure of thoracic duct ligation [30]. Moreover, in this series of 24 patients, the lack of thoracic duct leakage was managed with nonoperative therapy with higher success rates [30]. No evidence is present to suggest a role for intravenous contrast material. When the underlying etiology of chylothorax is unknown or nontraumatic, the speed, sensitivity, and specificity of CT imaging can narrow the broader differential diagnosis. Discussion of the Imaging Modalities by Variant Variant 1: Chylothorax treatment planning: traumatic etiology. Traumatic chylothoraces are a result of direct injury to thoracic lymphatics.


Chylothorax Treatment Planning

Chylothorax Treatment Planning. Iatrogenic traumatic chylothorax complicates up to 4% of esophageal resections [1,2,4-7]. Lung cancer resections, cardiovascular surgeries, and Chylothorax Treatment Planning spinal surgeries can also be complicated by chylothorax, although at a lesser rate. Noniatrogenic causes of traumatic chylothorax include penetrating trauma, fracture-dislocation of the spine, and hyperflexion injuries [1,6,7]. Generally, the causative etiology is known in the traumatic setting. Sampling the pleural effusion confirms the diagnosis of chylothorax. Imaging a patient with a known traumatic chylothorax serves only to confirm the diagnosis and assist in therapeutic planning. Chest radiography In the setting of a traumatic injury to the thoracic duct, most commonly postoperative or mechanical trauma, chest radiographs can confirm the presence of pleural fluid and lateralize the process and are routinely acquired in the daily evaluation of supportive lines and tubes [19]. Ultrasound US can be helpful in the guidance of thoracentesis and intranodal injection during lymphangiography [21]. Otherwise, US has little, if any, diagnostic role in the setting of a known traumatic chylothorax. Conventional lymphangiography Conventional lymphangiography is the gold standard for visualization of lymph nodes, lymphatic vessels, cisterna chyli, the thoracic duct, and sites of injury [14,22,23]. Lymphangiography alone has been shown to be therapeutic in a small percentage of patients, irrespective of attempts at TDE or disruption [24-27]. When performed as a prelude to TDE, the combination is particularly effective in treating traumatic chylothorax, with technical and clinical success rates approaching 90% [5-9,11]. Nuclear lymphoscintigraphy Although nuclear lymphoscintigraphy may be able to confirm a lymphatic leak and identify the site, little evidence is present to support its routine use [31-33].


Chylothorax Treatment Planning

Chylothorax Treatment Planning. Moreover, this adds little to the clinical care of a patient as the traumatic etiology is usually known and any information gained would be redundant if conventional lymphangiography was performed as part of TDE. Magnetic resonance imaging chest and abdomen The diagnostic benefit of MRI is negated in the setting of traumatic chylothoraces. However, the ability of MRI to map the lymphatic system can be of benefit in select cases where identifying the cisterna chyli and/or thoracic duct is difficult or conventional lymphangiography is unsuccessful [40-43]. Computed tomography chest and abdomen CT imaging is able to visualize portions of lymphatic system but provides less anatomic detail than MRI [36,47,48]. If the etiology is known, CT of the chest and abdomen, with or without intravenous contrast material, has little value in that it does not help guide therapy directed at chylothorax in most cases. Variant 2: Chylothorax treatment planning: nontraumatic or unknown etiology. Nontraumatic chylothorax accounts for approximately 46% of chylothoraces and can be subcategorized as resulting from malignancy, as occurs in 18% of all chylothoraces, or nonmalignant etiologies, which account for 28% of all chylothoraces [1,2,6,7]. Of the malignant etiologies, lymphoma is the leading cause, accounting for 75% of all malignant chylothoraces. Nonmalignant, nontraumatic chylothorax has been described in lymphangioleiomyomatosis, sarcoidosis, cirrhosis, heart failure, nephrotic syndrome, venous thrombosis, filariasis, venolymphatic malformations, and a variety of other congenital, idiopathic, and systemic diseases. Approximately 9% of all chylous effusions are idiopathic [1,2,6,7]. Imaging a patient with either a nontraumatic chylothorax or a chylothorax of unknown etiology serves to narrow the differential diagnosis, further characterize the underlying cause and its severity, and assist in treatment planning.


Chylothorax Treatment Planning

Chylothorax Treatment Planning. Most patients with nontraumatic chylothoraces or chylothoraces of unknown etiologies present with acute respiratory illness (ARI), which consists of 1 or more of the following: cough, sputum production, chest pain, or dyspnea (with or without fever). The evaluation of ARI has been addressed by the American College of Radiology (ACR), and the imaging evaluation includes chest radiography and chest CT [50,51]. The consistent finding of chylothorax on initial imaging is the presence of a pleural effusion, which is a common medical problem with more than 50 recognized causes [52]. Pleural fluid studies are necessary for definitive diagnosis and to narrow the cause etiology of chylothorax. Ultrasound US reliably detects pleural fluid but cannot definitively discriminate between the types of pleural effusion and provides minimal additional information to narrow the differential diagnosis [20]. US can be helpful in the guidance of thoracentesis and intranodal injection during lymphangiography [21]. Conventional lymphangiography Conventional lymphangiography is the gold standard for visualization of lymph nodes, lymphatic vessels, cisterna chyli, and the thoracic duct and for detection of lymphatic leakage [14,22,23]. In a nontraumatic or idiopathic chylothorax, conventional lymphangiography may help diagnose lymphatic vessel diseases and anatomic abnormalities and prevent unnecessary procedures. However, compared with traumatic chylothorax and particularly in the setting of a systemic disease, conventional lymphangiography does not always elucidate the underlying etiology. Additionally, TDE is less clinically effective in a nontraumatic chylothorax unless thoracic duct occlusion or extravasation is present [6]. Nuclear lymphoscintigraphy Nuclear lymphoscintigraphy has only a few reports that suggest it may be able to localize the site of chylous leak, particularly if used with 3-D single-photon emission CT/CT techniques [31-33].


Workup of Pleural Effusion or Pleural Disease.  Introduction/Background Under normal circumstances, approximately 0.1 to 0.2 mL/kg body weight of pleural fluid resides in the pleural space [1]. Abnormal accumulation of pleural fluid is the most common clinical manifestation of pleural disease [2], typically caused by increased pulmonary capillary pressure, increased pleural membrane permeability, decreased oncotic pressure, or lymphatic obstruction [3]. Pleural effusions are categorized as transudative or exudative [4], with transudative effusions usually reflecting the sequala of a systemic etiology and exudative effusions usually resulting from a process localized to the pleura [5]. Common causes of transudative pleural effusions include congestive heart failure, cirrhosis, and renal failure, whereas exudative effusions are typically due to infection, malignancy, or autoimmune disorders [6], emphasizing the importance of prompt diagnosis to aid in patient management [7]. In general, physical examination findings have a lower positive likelihood ratio for detection of pleural effusions [8], supporting the use of imaging to aid in identification of clinically significant pleural effusions. When imaging pleural effusions, chest radiographs can typically detect >75 mL on the lateral view and >175 mL on the frontal view [9]. Thoracic ultrasound (US) can detect >20 mL of pleural fluid [10]. Chest CT can detect >10 mL of pleural fluid, and is considered the reference standard for imaging [11]. 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.


Workup of Pleural Effusion or Pleural Disease. OR 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 Workup of Pleural Effusion or Pleural Disease Discussion of Procedures by Variant Variant 1: Recent pneumonia with suspected parapneumonic effusion or empyema. Initial imaging. CT Chest With IV Contrast Current American Association for Thoracic Surgery consensus guidelines recommend CT chest with intravenous (IV) contrast in cases of suspected parapneumonic effusion (class IIa) [13]. A recent meta-analysis reported 5 chest CT findings most commonly associated with the diagnosis of empyema: pleural enhancement (sensitivity 84%, 95% confidence interval [CI], 62%-94%; specificity 83%, 95% CI, 75%-89%), pleural thickening (sensitivity 68%, 95% CI, 56%-77%; specificity 87%, 95% CI, 80%-92%), loculation (sensitivity 52%, 95% CI, 44%-59%; specificity 89%; 95% CI, 82%-94%), extrapleural fat proliferation (sensitivity 53%, 95% CI, 47%-60%; specificity 91%, 95% CI, 82%-96%), and increased attenuation of the extrapleural fat (sensitivity 39%, 95% CI, 32%-48%; specificity 97%, 95% CI, 94%-98%) [14]. Of note, these pooled sensitivities and specificities include CT chest with IV contrast or CT chest without IV contrast. Pleural enhancement has the highest area under curve for the diagnosis of empyema (0.86) and for distinguishing between simple parapneumonic effusion and empyema (0.83) [14].


Workup of Pleural Effusion or Pleural Disease. In a secondary analysis of the Multi-centre Intra-pleural Sepsis Trial (MIST) 2 trial of patients with laboratory proven pleural infection, the combination of parietal pleural enhancement and pleural thickening was seen in 98.7% of patients (95% CI, 92.8%-99.8%) on pleural-phase contrast-enhanced CT [15]. The presence of pleural enhancement with pleural gas/microbubbles [16] or larger pleural effusion size [17] also boosts the accuracy for identifying parapneumonic effusions requiring thoracentesis [16,17]. Parapneumonic effusions <2.5 cm in anteroposterior (AP) dimension can often be managed without thoracentesis [18]. From a technical perspective, acquiring the CT scan 60 seconds after the IV contrast bolus optimizes visualization of the pleura [19,20]. CT Chest Without and With IV Contrast There is no relevant literature to support the use of CT chest without and with IV contrast in the initial imaging of recent pneumonia with suspected parapneumonic effusion or empyema. CT Chest Without IV Contrast There is no relevant literature to support the use of CT chest without IV contrast in the initial imaging of recent pneumonia with suspected parapneumonic effusion or empyema. If a noncontrast CT is obtained, 4 out of 5 chest CT findings most commonly associated with the diagnosis of empyema in a recent meta-analysis may be ascertained without IV contrast: pleural thickening (sensitivity 68%, 95% CI, 56%-77%; specificity 87%; 95% CI, 80%-92%), loculation (sensitivity 52%, 95% CI, 44%-59%; specificity 89%; 95% CI, 82%-94%), fat thickening (sensitivity 53%, 95% CI, 47%-60%; specificity 91%; 95% CI, 82%-96%), and fat stranding (sensitivity 39%, 95% CI, 32%- 48%; specificity 97%; 95% CI, 94%-98%) [14]. Of note, these pooled sensitivities and specificities include CT chest with IV contrast or CT chest without IV contrast.


Workup of Pleural Effusion or Pleural Disease. Gas in the pleural space is another specific marker for complicated parapneumonic effusion, with specificities ranging from 81% (95% CI, 73%-87%) to 96% (95% CI, 86%-99%) [16,17]. Parapneumonic effusions <2.5 cm in AP dimension can often be managed without thoracentesis [18]. CTA Chest With IV Contrast There is no relevant literature to support the use of CTA chest with IV contrast in the initial imaging of recent pneumonia with suspected parapneumonic effusion or empyema. Note that CTA often employs contrast timing that is earlier than 60 seconds and therefore does not allow sufficient time for pleural enhancement. MRI Chest Without and With IV Contrast There is no relevant literature to support the use of MRI chest without and with IV contrast in the initial imaging of recent pneumonia with suspected parapneumonic effusion or empyema in adults. In case reports, MRI chest without and with IV contrast has been used as an adjunctive modality for the diagnosis of empyema necessitans [21]. In pediatric patients, limited data suggests MRI is noninferior to CT chest with IV contrast for the diagnosis of empyema [22-24]. MRI Chest Without IV Contrast There is no relevant literature to support the use of MRI chest without IV contrast in the initial imaging of recent pneumonia with suspected parapneumonic effusion or empyema. In small studies, diffusion weighted imaging [25] Workup of Pleural Effusion or Pleural Disease and T1 mapping [26] have shown promise in distinguishing exudative from transudative pleural effusions without contrast material. Radiography Chest Consensus recommendations endorse chest radiography as the initial imaging modality for patients with recent pneumonia and suspected pleural effusion [27,28]; however, there are limited empiric data to support these recommendations. Posteroanterior (PA) and lateral radiographs have a significantly greater sensitivity for the detection of parapneumonic effusions than single-view AP radiographs.


Workup of Pleural Effusion or Pleural Disease. In a retrospective analysis of patients from the Community-Acquired Pneumonia Organization international cohort study, PA and lateral radiographs had a sensitivity of 83.9% versus 67.3% for AP radiographs when using CT as the reference standard [29]. Single-view PA, single lateral view, or single-view AP radiographs have been shown to have statistically equivalent sensitivities for detection of parapneumonic effusions [30], with most missed parapneumonic effusions occurring in patients with coexistent lower lobe consolidation [30]. The specificity of chest radiography for the detection of complicated parapneumonic effusions, defined as those requiring thoracentesis, is modest. For example, in a retrospective study of 66 patients undergoing thoracentesis for parapneumonic effusions, chest radiography had a specificity of 60% for the detection of complicated parapneumonic effusions [31]. US Chest Identification of a pleural effusion for possible US-guided thoracentesis is currently the primary reason for chest US [32]. Current American Association for Thoracic Surgery consensus guidelines recommend thoracic US for the diagnostic evaluation of pleural space infection (class I), typically occurring in patients with prior imaging documenting the presence of a pleural effusion [13]. US findings of septations [33,34], increased echogenicity of the pleural effusion [31,35], pleural thickening [36], and microbubbles [37] are associated with parapneumonic effusion/empyema. A retrospective study of 66 patients with suspected parapneumonic effusion found that US chest had a significantly higher specificity (90%, 95% CI, 76.3%-97.2%) and a nonsignificant difference in sensitivity (69.2%, 95% CI, 48.2%-87.7%) compared with CT chest for the diagnosis of complicated parapneumonic effusion [31]. A retrospective comparison of US chest and CT chest in pediatric patients found similar accuracy for the detection of parapneumonic effusion [38].


Workup of Pleural Effusion or Pleural Disease. CT Chest With IV Contrast CT chest with IV contrast or CTA chest with IV contrast is regarded as the reference standard for the noninvasive assessment of thoracic injury in patients with chest trauma, regardless of severity, and a clinical indication for imaging [42]. The goal of CT chest with IV contrast is to identify hemothorax and contrast extravasation. The incidence of pleural effusion on chest CT in minor blunt trauma is unknown; however, in a retrospective study of 2,440 multiple trauma patients undergoing whole body CT with IV contrast, 2.2% had an incidental pleural effusion [43]. In a secondary analysis of the prospective observational NEXUS Chest and NEXUS Chest CT studies of patients with major or minor blunt trauma, 1.8% of patients had a hemothorax on CTA chest with IV contrast [44]. CT Chest Without and With IV Contrast There is no relevant literature to support the use of CT chest without and with IV contrast in the initial imaging of recent minor blunt trauma with suspected pleural effusion. CTA Chest With IV Contrast CTA chest with IV contrast or CT chest with IV contrast is regarded as the reference standard for the noninvasive assessment of thoracic injury in patients with chest trauma and a clinical indication for imaging [42]. The goal of Workup of Pleural Effusion or Pleural Disease CTA chest with IV contrast is to identify hemothorax and contrast extravasation. The incidence of pleural effusion on chest CT in minor blunt trauma is unknown; however, in a retrospective study of 2,440 multiple trauma patients undergoing whole body CT with IV contrast, 2.2% had an incidental pleural effusion [43]. In a secondary analysis of the prospective observational NEXUS Chest and NEXUS Chest CT studies of patients with major or minor blunt trauma, 1.8% of patients had a hemothorax on CTA chest with IV contrast [44].


Workup of Pleural Effusion or Pleural Disease. Image-Guided Aspiration Chest There is no relevant literature to support the use of image-guided aspiration chest in the initial imaging of recent minor blunt trauma with suspected pleural effusion. MRI Chest Without and With IV Contrast There is no relevant literature to support the use of MRI chest without and with IV contrast in the initial imaging of recent minor blunt trauma with suspected pleural effusion. MRI Chest Without IV Contrast There is no relevant literature to support the use of MRI chest without IV contrast in the initial imaging of recent minor blunt trauma with suspected pleural effusion. Radiography Chest Chest radiography is considered a first-line imaging test for patients with chest trauma and a clinical indication for imaging [46]. In the prospective NEXUS Chest CT trial, blunt trauma patients without an abnormal chest radiograph and 6 clinical criteria could avoid an unnecessary chest CT (sensitivity 99.2%; 95% CI, 95.4%-100%, specificity 20.8%; 95% CI, 19.2%-22.4%) [47]. A meta-analysis of the pooled sensitivity and specificity of chest radiographs for the detection of hemothorax in patients with chest trauma was 54% (95% CI, 33%-75%) and 99% (95% CI, 94%-100%), respectively, when using chest CT as the reference standard [48]. A study of 24 patients using only PA radiographs found a similar sensitivity of 62.5% and specificity of 100% for the detection of pleural effusions in patients with chest trauma [49]. In 2 prospective series of patients with minor blunt thoracic trauma and an initial normal chest radiograph, 7.4% to 11.8% had a pleural effusion on follow-up radiography within 2 weeks, clinically ascribed as a delayed hemothorax [39,40]. A delayed hemothorax on chest radiographs after minor blunt thoracic trauma was significantly more likely in patients with at least 1 fracture between the third and ninth ribs [50]. US Chest The sensitivity and specificity of chest US for only minor blunt trauma has not been reported.


Workup of Pleural Effusion or Pleural Disease. Identification of a hemothorax for possible US-guided thoracentesis is the primary reason for chest US [32]. A recent meta-analysis reported chest US had a 60% sensitivity (95% CI, 31%-86%) and a 98% specificity (95% CI, 94%-99%) for traumatic hemothorax [51]. Variant 3: Dyspnea, cough, or chest pain with suspected pleural effusion, noninfectious. Initial imaging. CT Chest With IV Contrast In patients with suspected malignant pleural effusion or suspected unilateral pleural effusion with an increased pretest probability of malignancy, CT chest with IV contrast is recommended [52,53], although this is not limited to patients with dyspnea, cough, or chest pain. Acquiring the CT scan 60 seconds after the contrast bolus improves visualization of pleural abnormalities associated with malignancy [19]. CT Chest Without and With IV Contrast There is no relevant literature to support the use of CT chest without and with IV contrast in the initial imaging of dyspnea, cough, or chest pain with suspected noninfectious pleural effusion. CT Chest Without IV Contrast There is no relevant literature to support the use of CT chest without IV contrast in the initial imaging of dyspnea, cough, or chest pain with suspected noninfectious pleural effusion. Heart failure, liver failure, and renal failure are common noninfectious causes of pleural effusion, and these patients may present with dyspnea, cough, or chest pain and undergo CT chest without IV contrast as part of their diagnostic workup [54,55]. CTA Chest With IV Contrast In patients with dyspnea, cough, or chest pain and suspected noninfectious pleural effusion, CTA chest with IV contrast is typically performed when there is clinical concern for pulmonary embolism [56] or aortopathy [57]. Pleural effusions in these patients are usually small and not associated with adverse clinical outcomes [57,58].


Workup of Pleural Effusion or Pleural Disease. Workup of Pleural Effusion or Pleural Disease MRI Chest Without and With IV Contrast There is no relevant literature to support the use of MRI chest without and with IV contrast in the initial imaging of dyspnea, cough, or chest pain with suspected noninfectious pleural effusion. Incidental pleural effusions have been reported in a minority of patients undergoing MRI with contrast for dyspnea, cough, or chest pain. For example, 6.6% (34/514) of patients had a moderate or large pleural effusion on contrast-enhanced MRA ordered for pulmonary embolism evaluation [59], and 4.3% (17/399) patients had a pleural effusion on stress cardiac MRI for possible acute coronary syndrome [60]. MRI Chest Without IV Contrast There is no relevant literature to support the use of MRI chest without IV contrast in the initial imaging of dyspnea, cough, or chest pain with suspected noninfectious pleural effusion. Radiography Chest Consensus recommendations endorse chest radiography as the initial imaging modality for patients with suspected noninfectious pleural effusion [7,61]; however, there are limited empiric data to support these recommendations. US Chest Identification of a pleural effusion for possible US-guided thoracentesis is currently the primary reason for chest US [32]. Chest US is increasingly used as part of the diagnostic pathway for patients in the emergency department [62] and in the intensive care setting [63]. A recent meta-analysis found that chest US had a pooled sensitivity of 91% (95% CI, 83%-96%) and specificity of 92% (95% CI, 82%-97%) using CT as the reference standard for identification of pleural effusion in patients in the intensive care unit [63]. Adding chest US to the conventional diagnostic pathway has been shown to reduce the time to final diagnosis in the emergency department in patients with infectious and noninfectious causes of dyspnea [64]. Variant 4: Pleural effusion incidentally detected on incomplete thoracic imaging study. Next imaging study.


Workup of Pleural Effusion or Pleural Disease. The frequency of an incidental pleural effusion detected on an incomplete thoracic imaging study including neck, spine, and abdomen varies based on the indication and type of imaging modality, in the range of 1% to 5% [65-71]. The clinical significance of these incidental pleural effusions is variable. In a retrospective study of patients undergoing run-off CTA, 4.2% (9/214) had an incidental pleural effusion, leading to the diagnosis of pneumonia in 22% (2/9) and optimization of heart failure therapy in 44% (4/9) [72]. However, in a study of 352 patients undergoing MRA of the abdomen, pelvis, and lower extremities, 2.9% had an incidental pleural effusion, and no patients required follow-up diagnostic testing or change in therapy. CT Chest With IV Contrast There is no relevant literature to support the use of CT chest with IV contrast as the next imaging study following a pleural effusion incidentally detected on prior abdominal imaging. The recommendation for a follow-up CT chest with IV contrast should be based on clinical assessment (eg, clinical suspicion of malignancy). CT Chest Without and With IV Contrast There is no relevant literature to support the use of CT chest without and with IV contrast as the next imaging study following a pleural effusion incidentally detected on prior abdominal imaging. The recommendation for a follow- up CT chest without and with IV contrast should be based on clinical assessment. CT Chest Without IV Contrast There is no relevant literature to support the use of CT chest without IV contrast as the next imaging study following a pleural effusion incidentally detected on prior abdominal imaging. The recommendation for a follow-up CT chest without IV contrast should be based on clinical assessment (eg, clinical suspicion of malignancy).


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome.  Introduction/Background Thoracic outlet syndrome (TOS) denotes the clinical entity that occurs with compression of the brachial plexus, subclavian artery, and/or subclavian vein at the superior thoracic outlet. There are three distinct spaces that can be implicated in TOS. Narrowing of each space results in slightly different presentations because of differing severity of impingement on the transiting neurovascular structures [1,2]. The costoclavicular triangle consists of the clavicle superiorly, the anterior scalene muscle posteriorly, and the first rib inferiorly. All three neurovascular structures pass through this space. Narrowing of this space tends to cause venous symptoms, frequently denoted venous TOS (vTOS), with varying degrees of additional symptoms due to arterial or brachial plexus compression. The interscalene triangle consists of the anterior scalene muscle, middle scalene muscle, and first rib. Trunks of the brachial plexus and the subclavian artery pass through this space; narrowing here causes neurological dominant TOS (nTOS), arterial dominant (aTOS), or combinations of both. The pectoralis minor space, defined by the pectoralis minor muscle anteriorly and chest wall posteriorly, is essentially an extension of the thoracic outlet and can result in varying degrees of compression similar to the costoclavicular space. During extreme shoulder abduction, the costoclavicular space is naturally narrowed. Anatomical variants such as a cervical rib can cause narrowing of the scalene triangle. Other possible sources of compression include anomalous first rib, C7 transverse process, or post-traumatic changes from prior clavicular or rib fractures. In patients who perform activities that require repetitive upper-extremity movement, such as swimming or throwing, or in patients who are not involved in excessive overhand motion but who have an anatomic predisposition to TOS, repetitive stress can lead to symptoms of TOS [3].


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. The subclavius muscle may hypertrophy, further narrowing the costoclavicular space, and the repetitive stress leads to thickening and fibrosis, notably in the subclavian vein wall, with restrictive fibrotic tissue surrounding the vein. Eventually, there is damage of the intima, resulting in luminal narrowing and a scarred, thrombogenic surface within the vein. Arterial changes in TOS similarly include intimal damage and thrombosis, with additional concerns of distal embolization and aneurysm formation. Neurological symptoms include chronic arm and hand paresthesia, numbness, or weakness. Although the exact prevalence of TOS is unknown, symptomatic TOS has been estimated to be 10 per 100,000 [4]. The current management of TOS is variable [5-11]. Understanding the various anatomic spaces, causes of narrowing, and resulting neurovascular changes are important in choosing and interpreting radiological imaging, which may be performed to help diagnose TOS and plan for intervention. This document has separated imaging appropriateness based on neurogenic, arterial, or venous symptoms, acknowledging that some patients may present with combined symptoms that may require more than one study to fully resolve. Additionally, in the postoperative setting, a new symptom may indicate a complication. Consultation aResearch Author, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts. bMassachusetts General Hospital, Boston, Massachusetts. cPanel Chair, Massachusetts General Hospital, Boston, Massachusetts. dPanel Chair, University of Chicago, Chicago, Illinois. ePanel Chair, University of Utah, Salt Lake City, Utah. fPanel Vice-Chair, Emory Healthcare, Atlanta, Georgia. gUC San Diego Health, San Diego, California. hThe University of Texas MD Anderson Cancer Center, Houston, Texas. iScripps Green Hospital, La Jolla, California; Society for Vascular Surgery. jMayo Clinic, Rochester, Minnesota. kUniversity of Alabama at Birmingham, Birmingham, Alabama.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. lMayo Clinic, Rochester, Minnesota. mUniversity of Virginia, Charlottesville, Virginia. nUniversity of California Los Angeles, Los Angeles, California; American Academy of Neurology. oVanderbilt University Medical Center, Nashville, Tennessee; American College of Chest Physicians. pLoyola University Medical Center, Maywood, Illinois. qUT Southwestern Medical Center, Dallas, Texas. rDuke University School of Medicine, Durham, North Carolina; The Society of Thoracic Surgeons. sUT Southwestern Medical Center, Dallas, Texas. tSpecialty Chair, Atlanta VA Health Care System and Emory University, Atlanta, Georgia. uSpecialty Chair, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin. vSpecialty Chair, UMass Memorial Medical Center, Worcester, Massachusetts. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: publications@acr.org Thoracic Outlet Syndrome with a radiologist may be useful at the time of examination ordering to optimize the study for the prevailing clinical symptom. When contrast is indicated, scan acquisition is typically performed with a contralateral antecubital intravenous (IV) injection, with either an empiric scan delay of 15 to 20 seconds or bolus tracking over the ascending aorta [12,13]. Some centers add the additional step of placing the contralateral arm in abduction (with the symptomatic ipsilateral arm in the neutral position) in order to minimize streak artifact [14]. All elements are essential: 1) timing, 2) reconstructions/reformats, and 3) 3-D renderings. Standard CTs with contrast also include timing issues and recons/reformats. Only in CTA, however, is 3-D rendering a required element.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. This corresponds to the definitions that the CMS has applied to the Current Procedural Terminology codes. CT venography (CTV) is obtained separately for each arm position 120 to 180 seconds after IV injection of iodinated contrast [6] in order to obtain venous opacification. The contrast injection should be performed in either the contralateral arm or other location. Multiplanar reformations are then produced to evaluate the thoracic space and true axial compression of the vessel. Center-line and volume-rendered images may also be produced to aid in visualization. CTA chest and CTV chest specifically denote studies tailored to evaluating the chest and thoracic outlet. These include evaluation of central vessels as well as subclavian and axillary arteries and veins, respectively. This is distinct from CTA upper extremity and CTV upper-extremity protocols, which are designed to evaluate the entire limb peripherally to the level of the wrist. Contrast-enhanced 3-D MR angiography (MRA) techniques have been described at both 1.5T and 3T to assess for TOS [19]. Breath-hold arterial phase contrast-enhanced 3-D MRA and equilibrium phase imaging is obtained using a 3-D gradient-echo pulse sequence with fat suppression. These can be obtained in both neutral and stressed positions with the exact protocol customized to institutional needs. A coronal oblique 3-D slab of the MRA is often obtained covering bilateral subclavian and axillary vessels. Unenhanced mask imaging is followed by multiphase contrast-enhanced dynamic acquisition in the same orientation. Noncontrast time-of-flight MRA may be considered, particularly in patients with contraindications to gadolinium-based contrast; however, these techniques suffer from flow artifacts, which could lead to false diagnosis of stenosis or thrombosis [19]. Noncontrast MRA Thoracic Outlet Syndrome also requires long acquisition times when combined with postural maneuvers that may be difficult to achieve for patients with severe clinical symptoms.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Contrast-enhanced 3-D MR venography (MRV) techniques have been described at both 1.5T and 3T to assess for vTOS [19]. Breath-hold venous phase contrast-enhanced 3-D MRV and equilibrium phase imaging is obtained using a 3-D gradient-echo pulse sequence with fat suppression. These can be obtained in both neutral and stressed positions with the exact protocol customized to institutional needs. A coronal oblique 3-D slab is often obtained covering bilateral subclavian and axillary vessels. Unenhanced mask imaging is followed by multiphase contrast- enhanced dynamic acquisition in the same orientation. Noncontrast time-of-flight MRV may be considered, particularly in patients with contraindications to gadolinium-based contrast; however, these techniques suffer from flow artifacts that could lead to false diagnosis of stenosis or thrombosis [19]. Noncontrast MRV also requires long acquisition times when combined with postural maneuvers that may be difficult to achieve for patients with severe clinical symptoms. CTA chest and CTV chest specifically denote studies tailored to evaluate the chest and thoracic outlet. These include evaluation of central vessels as well as subclavian and axillary arteries and veins, respectively. This is distinct from CTA upper extremity and CTV upper-extremity protocols, which are designed to evaluate the entire limb peripherally to the level of the wrist. Discussion of Procedures by Variant Variant 1: Neurogenic thoracic outlet syndrome. Initial imaging and follow-up imaging after surgery or intervention. Arteriography Upper Extremity Selective upper-extremity arteriography is unable to directly image neurologic structures. This procedure is therefore not considered a first-line test for nTOS pre- or postoperatively. Catheter Venography Upper Extremity Dedicated endovascular catheter venography is unable to directly image neurologic structures. This procedure is therefore not considered a first-line test for nTOS pre- or postoperatively.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. CT Chest CT for the evaluation of nTOS is limited by the lack of resolution of neural structures, although evaluation of the space sizes gives secondary indicators that may aid in diagnosis [13]. The goal is to demonstrate anatomical narrowing that could cause neurovascular compression. Findings include effacement of fat within the respective space and distortion or narrowing of the space with provocative or stress positioning. To also define adjacent vascular structures, a CT with IV contrast is sufficient for evaluation of nTOS [12,13]. CT allows quantification of the change in costoclavicular or interscalene spaces with provocative maneuvers [12,13], the presence of bony abnormalities [20,21], or superior sulcus pathology [22]. CT without IV contrast may be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and assess adequate decompression. If there is a clinical concern for arterial or venous compromise, postintervention for patients with nTOS, imaging should be guided by those Variants. CTA Chest CTA does not provide further evaluation of the neurologic structures as compared with chest CT. If there are overlapping symptoms with aTOS or vTOS, review of the other Variants in this document may help with protocol optimization. CTV Chest CTV does not provide further evaluation of the neurologic structures as compared with chest CT. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. MRI Chest MRI has inherent advantages over ultrasound (US) in its ability to delineate extravascular anatomy, particularly in anatomic sites with poor sonographic windows, and MRI has advantages over CT in its characterization and differentiation of soft tissues. Thoracic Outlet Syndrome


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. For evaluation of patients with nTOS, definition of the brachial plexus and cervical spine and dynamic evaluation of neurovascular bundles in the costoclavicular, interscalene, and pectoralis minor spaces are required. Noncontrast MRI can be sufficient to diagnose nTOS. In one study, for patients with nTOS, the neurovascular bundle was most commonly compressed in the costoclavicular space, mostly secondary to position, and very rarely compressed in the pectoralis minor space [16]. The cause of TOS was congenital bone variations in 36%, congenital fibromuscular anomalies in 11%, and positional in 53%. In 5%, there was unilateral brachial plexitis in addition to compression of the neurovascular bundle. Severe cervical spondylosis was noted in 14%, contributing to TOS symptoms [16]. MRI without IV contrast may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and assess adequate decompression. Postcontrast imaging may additionally be useful to assess the soft tissues for inflammatory or neoplastic conditions. MRA Chest Contrast-enhanced 3-D MRA techniques do not provide evaluation of the neurologic structures. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. MRV Chest Contrast-enhanced 3-D MRV techniques do not provide adequate evaluation of the neurologic structures. This procedure is therefore not considered a first-line test for nTOS pre- or postoperatively. Radiography Chest Chest radiography is frequently used as an initial imaging modality in suspected TOS. Osseous abnormalities associated with TOS are frequently easily diagnosed by chest radiographs. These include first rib anomalies [20], cervical ribs [23], congenital osseous malformations [24,25], and focal bone lesions [26].


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Soft-tissue lesions, such as lung neoplasms [27], may also be evaluated, although the negative predictive value of chest radiographs is low, such that cross-sectional imaging is a necessary part of a complete TOS workup. In the postoperative setting, radiographs may be useful to confirm osseous changes and evaluate for postoperative complications, such as pneumothorax. US Duplex Doppler Subclavian Artery and Vein US is widely used as an imaging modality in the initial evaluation of patients with suspected arterial or venous pathology. Although many patients with nTOS have additional symptoms due to arterial or venous compression, US is not as valuable in assessing direct neurological involvement. Real-time duplex US can be used to evaluate the cross-sectional area of the costocervical space with and without provocative maneuvers [28]. Diagnosis of compressive effects upon the brachial plexus is a challenge [29], and symptoms of TOS may unmask a deeper regional pathology such as a Pancoast tumor or cervical spondylopathy, requiring further imaging. If there is reason to believe that symptoms could be related to hypertrophy of the anterior scalene muscles, US could be used for guidance to inject anesthetic in an attempt to confirm nTOS [30]. The procedure is considered diagnostic of nTOS if the patient experiences relief of symptoms after the injection. In the postoperative setting, US can be useful to evaluate vessel patency and complications such as postoperative hematoma or fluid collection. Variant 2: Venous thoracic outlet syndrome. Initial imaging and follow-up imaging after surgery or intervention. Arteriography Upper Extremity Selective upper-extremity arteriography may be used to evaluate extrinsic compression of the subclavian artery; however, it does not provide diagnostic assessment of the subclavian vein. This procedure is therefore not considered a first-line test for vTOS.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. In the postprocedure setting, catheter arteriography may be performed to evaluate and intervene on suspected or confirmed arterial complications. Catheter Venography Upper Extremity Diagnostic venography may be performed for suspected vTOS in which the veins of the affected extremity are catheterized, and contrast injection is performed via the catheter during digital subtraction acquisition in both neutral and stressed positions. Typical findings include narrowing of the subclavian vein with appearance of venous collateral vessels. These are generally seen projecting over the thorax or across the neck. Total occlusion of the subclavian vein may be present in chronic or acute TOS, and all findings may be present on only stressed position venography or at stress and neutral positions. Thoracic Outlet Syndrome As part of the evaluation for surgical decompression, patients may also undergo contralateral venography as well as catheter-directed thrombolysis. Angioplasty is not typically performed in the chronic setting, and at some centers, it is generally avoided prior to surgical decompression. In patients with total or near-total subclavian vein occlusion, endovascular recanalization of the subclavian vein may be attempted, and, if successful, a peripherally inserted central venous catheter is occasionally inserted and positioned so that it courses across the newly recanalized venous segment. It is then left indwelling until after surgical decompression is performed so as to preserve a route of intraluminal access across the diseased subclavian vein segment. One advantage of venography as a diagnostic tool is that other presurgery interventions may be performed, including intravascular thrombolysis, thrombectomy, and angioplasty. For postsurgical decompression, catheter venography is often indicated for evaluation of residual narrowing and possible US angioplasty of the diseased or stenosed segment with the external compression [31,32].


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Intravascular US (IVUS) may be used as an adjunct in the postoperative setting to evaluate residual lumen size and presence of webs and has been shown to detect a higher degree of stenosis compared with venography alone [33]. CT Chest For noncontrast chest CT, the goal is to demonstrate anatomical narrowing that could cause vascular compression. Findings include effacement of fat within the respective space and distortion or narrowing of the space with provocative or stress positioning. Given the enhanced visualization of vascular structures with contrast, chest CT with IV contrast is preferred for evaluation of vTOS, and the acquisition is typically performed with a contralateral antecubital injection of contrast material. Chest CT without IV contrast may be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and assess adequate decompression. However, chest CT with IV contrast has the advantage of providing assessment of vascular patency, which is a potential complication in the postintervention setting for patients with vTOS. CTA Chest CTA is performed to evaluate arterial compression and is therefore of limited use in the evaluation of vTOS. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. CTV Chest CTV is performed to evaluate venous compression in neutral and elevated arm positions. Venous compression is often present with abduction in asymptomatic patients, and therefore this finding alone may be insufficient to diagnose vTOS. Venous thrombosis and presence of collateral venous circulation essentially bypassing the thoracic outlet confirms the existence of hemodynamically significant vTOS [1].


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Multiple studies have demonstrated the utility of CTV with IV contrast in evaluation of the upper-limb veins; however, reliance on axial slices alone can lead to misrepresentation of the degree of any stenosis, with one study showing underestimation of stenosis found in 43% of transverse CT scans but only in 10% of sagittal reformations. Overestimation of stenosis was also more frequent on surface displays with 3-D shading (16%) than on volume- rendered images (7%) [12], thus advancing the case for evaluation of these studies using these multiplanar tools in addition to standard reformations. CTV may be performed in the postintervention setting to evaluate interval changes in the thoracic outlet, assess adequate decompression, and follow-up on vessel patency or complications. Recurrent or persistent venous thrombosis may require reintervention. MRI Chest MRI for vTOS is performed to delineate anatomy and evaluate the pertinent anatomic spaces in both neutral and arms-abducted positions. Noncontrast MRI findings include effacement of fat adjacent to the subclavian vein. T1- weighted imaging performed in sagittal and axial planes can also demonstrate causative lesions, including cervical ribs, congenital fibromuscular anomalies, and muscular hypertrophy. Venous compression has been routinely demonstrated in all 3 compartments of the thoracic outlet in both asymptomatic and symptomatic populations when the arms were abducted [17]. Therefore, a finding of compression on abduction must be interpreted carefully. In symptomatic patients, venous thrombosis and collateral circulation Thoracic Outlet Syndrome are detected in both neutral and stressed arm positions, suggesting these findings are more reliably diagnostic of vTOS. They represent an objective, but likely chronic, finding of clinically significant venous compression.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Given the need to assess the subclavian vein as well as venous collaterals in vTOS, noncontrast MRI is insufficient alone; the addition of IV contrast, particularly when an MRV protocol is performed, provides optimal assessment. The combination of soft-tissue and vascular assessment provided by MRI with IV contrast makes it an excellent modality when compared with US and CT; however, the longer acquisition times may prove difficult for highly symptomatic patients. MRI with IV contrast may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and assess adequate decompression. MRA Chest MRA is not optimized for evaluation of the venous structures. If there are overlapping symptoms, review of the other variants in this document may help with protocol optimization. Interestingly, in one study [19], all patients with arterial compression were found to have venous compression during arm abduction. In patients with venous compression on one side, 71% had significant bilateral venous compression. Of these patients with bilateral imaging findings, only 21% had bilateral clinical symptoms or findings suggestive of TOS. Therefore, MRA has the potential to overdiagnose vTOS, and clinical symptoms must be taken into account. MRA may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet, assess adequate decompression, and confirm arterial patency. MRV Chest MRV is commonly performed in conjunction with MRI chest [34-36]. The primary MRV finding is narrowing of the subclavian vein; however, other findings, such as complete occlusion, collateral vessel formation, and visualization of thrombus, aid in the diagnosis of vTOS. Interestingly, in one study [19], all patients with arterial compression were found to have venous compression during arm abduction. In patients with venous compression on one side, 71% had significant bilateral venous compression.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Of these patients with bilateral imaging findings, only 21% had bilateral clinical symptoms or findings suggestive of TOS. Therefore, MRV has the potential to overdiagnose vTOS, and clinical symptoms must be taken into account. MRV may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet, assess adequate decompression, and confirm arterial patency. Radiography Chest Because of the importance of identifying osseous structures that may impinge on the spaces of the thoracic outlet, chest radiography is useful in performing a robust evaluation for all types of TOS. As opposed to directly evaluating vascular structures, osseous abnormalities associated with TOS are frequently easily diagnosed by chest radiographs. These include first rib anomalies [20], cervical ribs [23], congenital osseous malformations [24,25], and focal bone lesions [26]. In the postoperative setting, radiographs may be useful to confirm osseous changes and evaluate for postoperative complications such as pneumothorax. US has a longstanding and well-documented role in the diagnosis of upper-extremity DVT [5,39], a common presentation of vTOS in the acute setting. Although the main advantage of US is the ability to directly compare between provocatively induced symptoms and concurrent direct vessel visualization, there is debate in the literature as to the significance of imaging findings, particularly with respect to maneuvers to minimize the thoracic outlet and associated spaces [28,37,40]. It is important to consider that certain etiologies of vTOS due to deeper pathology, such as Pancoast tumor or cervical spondylopathy, may require further investigation with cross-sectional imaging. Thoracic Outlet Syndrome In the postoperative setting, US can be useful to evaluate vessel patency and complications, such as postoperative hematoma or fluid collection. Variant 3: Arterial thoracic outlet syndrome. Initial imaging and follow-up imaging after surgery or intervention.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Arteriography Upper Extremity Conventional catheter-based arteriography is effective at locating the exact point of vascular compression. In order to perform complete arteriography, catheter injection of contrast must be made from the aortic arch or the proximal subclavian artery. Injections and digital subtraction angiographic acquisitions are performed in both the neutral and abducted positions to assess dynamic changes. Vascular access is typically obtained from the femoral artery, although a radial artery approach can be considered. Even as a diagnostic tool alone, arteriography carries some risk. Because of its invasive nature and lack of information regarding surrounding structures, catheter-based angiography is largely only pursued if an endovascular intervention is envisioned. In the postintervention setting, catheter arteriography can provide definitive evaluation of arterial compression, occlusion, or other complication, such as dissection or aneurysm formation. This modality has the added advantage of possible immediate endovascular intervention. Catheter Venography Upper Extremity Diagnostic venography is not optimized for arterial evaluation. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. CT Chest For noncontrast CT, the goal is to demonstrate anatomical narrowing that could cause vascular compression. Findings include effacement of fat within the respective space and distortion or narrowing of the space with provocative or stress positioning. In a comprehensive study [13], a statistically significant difference was found between the distribution of the distances measured in the neutral and abducted positions in patients with arterial stenosis versus those without arterial stenosis. CT without IV contrast may be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and assess adequate decompression.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. However, CT with IV contrast has the advantage of providing assessment of vascular patency, which is a potential complication in postintervention setting for patients with aTOS. CTA Chest CTA is performed to evaluate arterial compression in neutral and elevated arm positions. An indentation of the anterior wall of the subclavian artery as it passes around the anterior scalene muscle may be observed [13] as well as displacement of the subclavian vessels. Arterial compression is assessed by using arterial cross-sections produced by sagittal reformation of data. Sagittal reformation can show the location and severity of the arterial compression, and volume-rendered images allow simultaneous analysis of bones and subclavian artery. Arterial stenosis is expressed as the percentage of reduction of the cross-sectional area or the diameter of the artery [1]. Multiple studies have demonstrated the utility of CT in evaluation of the upper-limb arteries and veins; however, reliance on axial slices alone can lead to misrepresentation of the degree of any stenosis, with one study showing underestimation of stenosis found in 43% of transverse CT scans but only 10% of sagittal reformations. Overestimation of stenosis was also more frequent on surface displays with 3-D shading (16%) than on volume rendered images (7%) [12], advancing the case for evaluation of these studies on vascular workstations. For arterial compression, there is evidence of good correlation of CT findings with operative findings and results of decompression [41]. CTA may be performed in the postintervention setting to evaluate interval changes in the thoracic outlet, assess adequate decompression, and follow-up vessel patency or complications. Recurrent or persistent venous thrombosis may require reintervention. CTV Chest CTV is performed for evaluation of venous compression. This specific modality is therefore of limited use in aTOS.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. Thoracic Outlet Syndrome MRI Chest MRI for aTOS is performed to delineate anatomy and evaluate the pertinent anatomic spaces in both neutral and arms-abducted positions. Noncontrast MRI findings include effacement of fat adjacent to the subclavian vein. T1- weighted imaging performed in sagittal and axial planes can also demonstrate causative lesions, including cervical ribs, congenital fibromuscular anomalies, and muscular hypertrophy. Given the need to assess the subclavian artery in aTOS, noncontrast MRI would be insufficient, with contrast- enhanced MR arteriography providing optimal assessment. The combination of soft-tissue and vascular assessment provided by MRI with contrast makes it an excellent modality when compared with US and CT; however, the longer acquisition times may prove difficult for highly symptomatic patients. MRI with IV contrast may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and to assess adequate decompression. MRA Chest The primary MRA finding is narrowing of the subclavian artery; however, other findings, such as complete occlusion, collateral vessel formation, and visualization of thrombus, aid in the diagnosis of aTOS. MRA may help identify the severity of TOS and guide surgical or endovascular management [36]. If there is no evidence of compression on the abducted images, then imaging in the neutral position may be deferred. In the evaluation of TOS, if there is compression of the subclavian artery depicted on both sagittal T1-weighted and MRA, it may be denoted as aTOS. Further findings of aTOS that may be present include fixed or dynamic stenosis, aneurysm, mural thrombus, or distal emboli.


Thoracic Outlet Syndrome

Thoracic Outlet Syndrome. Numerous MRA techniques have been described including noncontrast MRA, including inversion recovery methods for patients unable or unwilling to have contrast [42], simultaneous bilateral MRA [34], and dual-gadolinium injection protocols [35]. Ancillary findings include possible etiologies of aTOS, frequently cervical or anomalous first rib, scalene muscle, fibromuscular bands, or pectoralis minor tendon, and anomalous course of the subclavian artery within the scalene muscle. MRA may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet, assess adequate decompression, and confirm arterial patency. MRV Chest MRV is not needed in patients with aTOS. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. Radiography Chest Because of the importance of identifying osseous structures that may impinge on the spaces of the thoracic outlet, chest radiography is useful in performing a robust evaluation for all types of TOS. As opposed to directly evaluating vascular structures, osseous abnormalities associated with TOS are frequently easily diagnosed by chest radiographs. These include first rib anomalies [20], cervical ribs [23], congenital osseous malformations [24,25], and focal bone lesions [26]. In the postoperative setting, radiographs may be useful to confirm osseous changes and evaluate for postoperative complications such as pneumothorax. US Duplex Doppler Subclavian Artery and Vein As with vTOS, US is an excellent initial study in the evaluation of aTOS. The subclavian and axillary arteries can be directly visualized and assessed for aneurysmal change, arterial stenosis, and thrombosis. Dynamic arterial blood flow can be assessed during abduction. Findings include decrease in arterial diameter, changes in peak velocity, or reproducible symptoms considered to be diagnostic of aTOS. Evaluation of the cross-sectional area of the costocervical space may also be performed [28].


Imaging of Invasive Breast Cancer

Imaging of Invasive Breast Cancer.  The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org Imaging of Invasive Breast Cancer and later-stage breast cancer prior to treatment. Additionally, we investigate the use of surveillance imaging after completion of treatment, both in the asymptomatic and symptomatic settings. In the post-treatment setting, we differentiate recommended imaging algorithms by symptomatology, because routine screening of asymptomatic patients after treatment for metastatic disease does not provide survival benefit, but early detection of nonmetastatic recurrence does improve overall outcomes [10]. Special Imaging Considerations Although still investigational, whole body diffusion weighted imaging and whole body fluorine-18-2-fluoro-2- deoxy-D-glucose (FDG) PET/MRI may show improved staging compared with whole body FDG-PET/CT in patients with later-stage disease [11-15]. Further studies are warranted to support their use in routine practice. Discussion of Procedures by Variant Variant 1: Newly diagnosed. Clinical stage I-IIA (early stage) breast cancer at presentation. Evaluation for locoregional disease (includes invasive ductal carcinoma [IDC], or invasive lobular carcinoma [ILC], or not otherwise specified [NOS]). Bone Scan Whole Body There is no evidence to support the use of Tc-99m bone scan whole body to evaluate for locoregional disease. CT Chest, Abdomen, and Pelvis With IV Contrast Few studies have evaluated the use of CT chest, abdomen, and pelvis with intravenous (IV) contrast to determine locoregional disease.


Imaging of Invasive Breast Cancer

Imaging of Invasive Breast Cancer. A study investigating the use of CT at evaluating locoregional disease, stages I to III, adding CT to mammogram, ultrasound (US) and physical examination correctly changed the surgical approach in 13.1% of patients, based on final pathology. However, CT failed to show any disease (false-negative) in 10.8% and had a low sensitivity for detecting multicentric and multifocal tumors [20]. CT Chest, Abdomen, and Pelvis Without IV Contrast There is no evidence to support the use of CT chest, abdomen, and pelvis without IV contrast to evaluate for locoregional disease. Digital Breast Tomosynthesis Diagnostic Diagnostic mammography and US together can assess for extent of disease and tumor size. These imaging tests are usually already completed as part of the diagnostic workup (prior to pathological diagnosis). However, mammography is limited by breast density. In a prospective study of 111 consecutive women with newly diagnosed breast cancer, sensitivity of 2-D mammography for malignancy decreased from 100% in breasts that are almost entirely fatty to 45% in extremely dense breasts [22]. In addition, 2-D mammography was more sensitive than US in detecting ductal carcinoma in situ (DCIS) and less sensitive in detecting ILC. Digital breast tomosynthesis (DBT) shows a higher overall sensitivity, compared with 2-D mammography, with a similar specificity. Overall sensitivity for DBT was 88.2% compared with 78.3% for 2-D mammography [23]. DBT also has a higher sensitivity for detecting multifocal, multicentric, and contralateral breast cancer [24,25]. The improved diagnostic performance of DBT over 2-D mammography in breast cancer staging was limited to women with nondense breasts in 1 study [24], but not others [25]. Due to patient positioning constraints, 2-D mammography and DBT have limited value for evaluating the axilla.


Imaging of Invasive Breast Cancer

Imaging of Invasive Breast Cancer. In a single-institution retrospective study of 3,944 patients with breast cancer, mammography improved the sensitivity over US alone for distinguishing N0 to N1 from N2 and N3, but at a lower specificity [35]. After the American College of Surgeons Oncology Group (ACOSOG) Z0011 trial supported the omission of axillary lymph node dissection in women with <3 positive sentinel lymph nodes undergoing breast-conserving surgery and radiation therapy, some providers now request that radiologists not image the axilla in the setting of clinically node-negative disease [36]. Even when neoadjuvant chemotherapy is planned, radiologists should be thoughtful about whether to image the axilla, discussing risks and benefits with surgical colleagues, because it is not universally recommended [37]. PET/CT has the potential to have greater sensitivity than US for axillary staging because it uses a functional measurement instead of an anatomic determination (eg, cortical thickness, loss of fatty hilum) as criteria for determining suspicion for metastatic disease [42]. Surgical studies show that 21% to 33% of T1 and 45% to 60% T2 tumors with normal appearing lymph nodes have metastatic disease on pathological examination [43]. Thus, studies have queried whether a functional measurement might be better. One study retrospectively evaluated PET/CT in 826 consecutive patients with breast cancer and showed a sensitivity and specificity of 74.7% and 83,4%, respectively, for identifying metastatic disease. Studies show a negative predictive value (NPV) from 87% to 88% [39,44]. Other studies show the sensitivity and specificity for detecting lymph node metastasis as 79% and 100%, respectively [38]. However, Sohn et al [45] showed a higher sensitivity for US plus fine-needle aspiration (FNA) at determining lymph node status than PET/CT (83% versus 80%, respectively).


Imaging of Invasive Breast Cancer

Imaging of Invasive Breast Cancer. Despite extensive scientific investigation, given the results above and the Z0011 trial, the role of PET/CT in determining locoregional extent is likely nominal. Mammography Diagnostic Diagnostic mammography and US together can assess for extent of disease and tumor size. These imaging tests are usually already completed as part of the diagnostic workup (prior to pathological diagnosis). However, mammography is limited by breast density. In a prospective study of 111 consecutive women with newly diagnosed breast cancer, the sensitivity of 2-D mammography for malignancy decreased from 100% in breasts that are almost Imaging of Invasive Breast Cancer entirely fatty to 45% in extremely dense breasts [22]. In addition, 2-D mammography was more sensitive than US in detecting DCIS and less sensitive in detecting ILC. DBT shows a higher overall sensitivity, compared with 2-D mammography, with similar specificity. Overall sensitivity for DBT was 88.2% compared with 78.3% [23]. DBT has a higher sensitivity for detecting multifocal, multicentric, and contralateral breast cancer [24,25]. The improved diagnostic performance of DBT over 2-D mammography in breast cancer staging was limited to women with nondense breasts in 1 study [24], but not others [25]. Due to patient positioning constraints, 2-D mammography and DBT have limited value for evaluating the axilla. In a single-institution retrospective study of 3,944 patients with breast cancer, mammography improved the sensitivity over US alone for distinguishing N0 to N1 from N2 and N3, but at a lower specificity [35]. After the ACOSOG Z0011 trial supported the omission of axillary lymph node dissection in women with <3 positive sentinel lymph nodes undergoing breast-conserving surgery and radiation therapy, some providers may request that radiologists not image the axilla in the setting of clinically node-negative disease [36].


Imaging of Invasive Breast Cancer

Imaging of Invasive Breast Cancer. Radiologists can be thoughtful about whether to image the axilla, discussing risks and benefits with surgical colleagues, because it is not universally recommended [37]. Mammography With IV Contrast Several retrospective studies have compared the sensitivity and specificity of CEM with conventional 2-D and 3-D mammography, US, and MRI. Overall, CEM and MRI are superior to DM and DM/DBT imaging [47]. The sensitivities between CEM and MRI are comparable, with some studies showing improved sensitivities with CEM [48] and some showing MRI to be superior [49,50]. Overall sensitivities ranged from 92% to 100% [16,49,51-53], including CEM detecting 92.3% of satellite masses and up to 100% of contralateral cancers [28]. CEM and MRI show similar abilities to estimate tumor size (r = 0.72-0.89 versus 0.65-0.84), but studies have shown an improved positive predictive value (PPV) of CEM (52%-93%) compared with MRI (28-60%) [16,49,53]. Despite increased specificity over MR, limitations of contrast mammography in determining disease extent include evaluation of the axilla and other nodal groups as well as chest wall involvement [47], and there is evidence against using CEM to determine disease extent in lobular cancer, due to lower conspicuity [54]. MRI Breast Without and With IV Contrast MRI breast is useful for detecting additional cancers in the ipsilateral or contralateral breast [16,55], particularly in women with dense breasts [23,56,57]. A meta-analysis of 22 studies investigated MRI screening of the contralateral breast in women with newly diagnosed breast cancer. This meta-analysis reported contralateral malignancies that were detected by MRI in 131 of 3,253 women. Thus, the summary estimate for incremental cancer detection rate was 4.1%. In studies in which pathologic tumor stage was reported, all but 2 tumors were in situ or stage I, and of those 2 tumors, 1 was node-negative ILC (42 mm). Summary estimates were as follows: MRI-directed additional