Thyroid Disease

Thyroid Disease. Painless thyroiditis has inhomogeneous hypoechogenic texture with decreased blood flow [19]. CT Neck CT is usually not used in the workup of thyrotoxicosis. MRI Neck MRI is usually not used in the workup of thyrotoxicosis. FDG-PET/CT Whole Body FDG-PET/CT imaging is not recommended as the initial imaging for the evaluation of a palpable thyroid nodule. Radionuclide Uptake and Scan Radioiodine uptake and scan can distinguish between high-uptake causes of thyrotoxicosis, such as Graves disease, toxic adenoma, and toxic multinodular goiter, and low-uptake causes, such as subacute thyroiditis and exogenous thyroid hormone [19,25]. The scan component is also helpful in differentiating between high-uptake causes, such as toxic adenoma, toxic multinodular goiter, and Graves disease (diffuse uptake) [19], as well as rarer causes, such as Marine-Lenhart syndrome (toxic nodule plus Graves) [26]. If radioiodine therapy is planned, the uptake component of the scan can then help determine the dose. Either I-123 or I-131 plus pertechnetate can be used [19]. If nodularity is present, I-123 is preferred so as to identify any hypofunctioning or isofunctioning nodules to target for biopsy [16]. In postpartum thyrotoxicosis, I-131 should be avoided [19]. Variant 4: Primary hypothyroidism. Initial imaging. Hypothyroidism is a condition of low thyroid hormone that is due to an underactive gland. Hypothyroidism can present with symptoms such as weight gain, cold intolerance, constipation, weakness, and fatigue, or be diagnosed as a laboratory abnormality. The treatment of hypothyroidism is thyroid hormone replacement. The most common etiology in the developed world (where dietary iodine supply is adequate) is Hashimoto thyroiditis, also known as chronic lymphocytic thyroiditis. Other etiologies include thyroidectomy, radioiodine therapy, external neck irradiation, iodine deficiency or excess, and drugs. There is no role for imaging in the workup of hypothyroidism in adults.


Thyroid Disease

Thyroid Disease. Imaging for thyroid morphology does not help differentiate among causes of hypothyroidism, and all causes of hypothyroidism will have decreased radioiodine uptake. US Thyroid There is no role for US imaging in the workup of hypothyroidism in adults. Imaging for thyroid morphology does not help differentiate among causes of hypothyroidism. CT Neck There is no role for CT imaging in the workup of hypothyroidism in adults. Imaging for thyroid morphology does not help differentiate among causes of hypothyroidism. MRI Neck There is no role for MRI in the workup of hypothyroidism in adults. Imaging for thyroid morphology does not help differentiate among causes of hypothyroidism. FDG-PET/CT Whole Body There is no role for FDG-PET/CT imaging in the workup of hypothyroidism in adults. Radionuclide Uptake and Scan There is no role for radioiodine uptake and scan in the workup of hypothyroidism in adults. Imaging for thyroid morphology does not help differentiate among causes of hypothyroidism, and all causes of hypothyroidism will have decreased radioiodine uptake. Variant 5: Preoperative evaluation of differentiated thyroid cancer. Surgery for DTC involves resection of the primary tumor and clinically significant lymph nodes. The goals of preoperative imaging are to evaluate for extrathyroidal invasion into surrounding structures (airway, esophagus, muscles) and for vascular encasement, and to identify lymph nodes in the lateral compartment >8 to 10 mm. Of note, the resection of larger nodal metastases, not micrometastases, is associated with improved survival, especially in patients <45 years of age [27]. Thyroid Disease In addition to the American Joint Committee on Cancer staging, which provides prognosis for survival, thyroid cancers are categorized by the American Thyroid Association into low, intermediate, and high risk, which provides risk for recurrence [16].


Thyroid Disease

Thyroid Disease. Preoperative staging and risk of recurrence both determine the need for RAI therapy after surgery and the protocol for tumor surveillance (Variant 6). US Thyroid US is a routine preoperative study in all patients with thyroid cancer. The role of US is to stage the primary tumor and cervical lymph nodes. In a retrospective study of patients who had primary surgery for thyroid cancer, US detected additional sites of metastatic disease not appreciated on physical examination in 20% of patients [28]. Compared to CT, US is more accurate in predicting early extrathyroidal tumor extension and multifocal bilobar disease [29]. US has excellent resolution for lymph node morphology. Most studies find US has higher diagnostic accuracy compared to CT for preoperative evaluation of nodal disease, especially for lateral compartment nodes [29-33]. Some centers use US for routine preoperative lymph node mapping and fine-needle aspiration of suspicious lymph nodes >8 to 10 mm [31]. CT Neck Preoperative CT with IV contrast is recommended as an adjunct to US for patients with clinical suspicion for advanced disease, including invasive primary tumor or clinically apparent multiple or bulky lymph node involvement [16]. CT is a better modality than US for delineating the extent of laryngeal, tracheal, esophageal, or vascular involvement [30,33]. CT is useful in defining the inferior border of disease and in determining the extent to which mediastinal structures are involved in cases with significant caudal spread. These inferior sites cannot be visualized on US. CT can also delineate bulky nodal disease and extranodal extension that involves muscle and blood vessels [34]. In particular, CT has higher sensitivity than US in detecting lymph node metastases in the central compartment and retropharyngeal space [32]. CT should be performed with iodinated contrast in order to better assess for tumor vascular encasement and small nodal metastases with hyperenhancement and necrosis.


Thyroid Disease

Thyroid Disease. Contrast is not contraindicated for DTC based on new studies on iodine retention [11,12] (see Special Imaging Considerations section above). Dual-phase CT imaging with and without IV contrast does not provide any additional information. MRI Neck MRI of the neck and mediastinum has the same role as CT in evaluating sites that are limited on US. The performance of MRI for imaging the neck and mediastinum has not been directly compared with CT on large numbers of thyroid cancer patients. Contrast is valuable for local staging and assessing suspicious lymph nodes. MRI has disadvantages of motion artifact in the lower neck from respiration and swallowing and is less sensitive than CT scan for the detection of small pulmonary nodules. FDG-PET/CT Whole Body A small prospective study compared diagnostic accuracy of FDG-PET/CT with US and contrast-enhanced CT. The sensitivity of PET for the detection of cervical lymph node metastases at all nodal levels is lowest for PET (30% versus 41% for US and 35% for CT) [35]. In general, because of the low avidity of well-differentiated thyroid cancers, FDG-PET/CT is not useful. Sensitivity of FDG-PET/CT scanning for malignancy may be slightly increased with TSH stimulation with recombinant human TSH but not enough to change management in most patients [36]. Whole-Body Scintigraphy Whole-body scintigraphy (WBS) has no role in the preoperative staging for DTC since the normal thyroid has very high iodine uptake and will take up most of the tracer. Octreotide Scan with SPECT or SPECT/CT Chest and Abdomen There is no role for indium-111 (In-111) somatostatin receptor scintigraphy at any stage of evaluation of DTC. Variant 6: Early imaging after treatment of thyroid cancer. After surgery, an early postoperative US within 6 to 12 months should be performed on all patients. Additional imaging depends on the extent of disease and surgery.


Thyroid Disease

Thyroid Disease. In patients with total thyroidectomy, extent of residual disease cannot be determined at surgery or on US, so WBS helps to decide if and how much RAI the patient should receive. WBS is also performed after RAI therapy. Thyroid Disease Imaging combined with serum thyroglobulin and thyroglobulin antibodies helps to categorize patients into risk groups according to response to therapy. Thyroglobulin testing with different cutoffs can be used to define response to therapy in patients after thyroidectomy with or without RAI and in those with lobectomy alone [37]. The choice of further imaging depends on the response to therapy based upon results from serum thyroglobulin testing and US performed in the first year after definitive treatment [15]. An excellent response to therapy is associated with a low recurrence risk (<5%) in patients with low- or intermediate-risk tumors. For these patients, if the serum thyroglobulin remains low, additional imaging is not indicated. For patients with thyroidectomy and ng/mL on thyroid hormone therapy in a RAI ablation, a low serum thyroglobulin is defined as a level of <0.2 sensitive assay or <1 ng/mL after TSH stimulation in patients who have undergone thyroidectomy and radioiodine ablation [16]. For patients with thyroidectomy or lobectomy but no RAI therapy, a low serum thyroglobulin is defined as a level of <0.2 ng/mL or <30 ng/mL, respectively [37]. However, if the serum thyroglobulin is elevated above the appropriate cutoff or if thyroglobulin antibodies are present and especially if they are rising, additional surveillance imaging is performed (see Variant 7 if there is concern for residual/recurrent disease on this basis). CT Neck CT is not recommended as the initial imaging study after treatment. See Variant 7 if there is concern for residual/recurrent disease. MRI Neck MRI is not recommended as the initial imaging study after treatment. See Variant 7 if there is concern for residual/recurrent disease.


Thyroid Disease

Thyroid Disease. FDG-PET/CT Whole Body FDG-PET/CT scanning is not recommended for routine surveillance if there is no residual disease. Whole-Body Scintigraphy If the patient receives RAI therapy, a post-therapy WBS should be performed to evaluate for residual disease. WBS is not utilized in low-risk patients without suspicion for recurrence and normal thyroid US [16]. It has no role in low-risk patients who have had a lobectomy. In intermediate- and high-risk patients, WBS has a role in evaluating initial response to radioiodine ablation. If there has been excellent response to therapy, WBS is usually not performed for ongoing surveillance. An uptake in the thyroid bed is sometimes performed to aid in detection of local recurrence and guide therapy. Either I-123 or I-131 can be used if a pretherapy scan is desired [16], as rates of successful remnant ablation are similar after I- 123 and I-131 [38,39]. If the choice exists, I-123 has better image quality [40,41]. Note that a post-therapy scan after radioiodine ablation using the radioactivity from the radioiodine ablation is recommended, as it upstages disease in 6% to 13% of cases [42-44]. Octreotide Scan with SPECT or SPECT/CT Chest and Abdomen There is no role for Octreotide scan with SPECT or SPECT/CT chest and abdomen at any stage of evaluation of DTC. Variant 7: Suspected recurrence of differentiated thyroid cancer. Suspected recurrence of DTC may present with a palpable neck abnormality or symptoms related to the organ of distant metastasis. More commonly, there may be no symptoms, but the patient may have a persistently elevated or rising thyroglobulin or rising thyroglobulin antibodies. After imaging, these patients can be categorized as elevated thyroglobulin with structural disease or elevated thyroglobulin with no detectable abnormality on imaging. The latter is thought to be due to small nodal metastases and can remain untreated for years. The 3 American Thyroid Association risk categories of recurrence help to guide imaging.


Thyroid Disease

Thyroid Disease. After initial excellent response, the risk for recurrence is 1% to 2% in low-risk patients, 2% to 4% in intermediate-risk patients, and 14% in high-risk patients [45-47]. In general, more imaging modalities are used to pursue recurrence in high-risk Thyroid Disease patients because distant metastases are more likely in these patients and negatively impacts on survival. Recurrence with a structural abnormality can be treated with neck dissection, repeat RAI therapy, external beam radiotherapy, and systemic therapy [16]. US Thyroid US of the neck is the first imaging investigation for suspected DTC recurrence and includes evaluation of the thyroid bed and cervical nodes. It can characterize palpable abnormalities in the neck and detect deeper neck masses that are not palpable [28]. CT Neck CT of the neck complements US of the neck for detection of additional metastases in the central compartment, in the mediastinum, and behind the trachea [29,33,48] or for assessment for invasive recurrent disease into the aerodigestive tract. CT should be performed with iodinated contrast in order to better assess for tumor vascular encasement and small nodal metastases with hyperenhancement and necrosis. Contrast is not contraindicated for DTC based on new studies on iodine retention [11,12] (see Special Imaging Considerations section above). Dual-phase CT imaging with and without IV contrast does not provide any additional information. CT Chest CT imaging of the chest should be considered in high-risk DTC patients with elevated serum thyroglobulin (>10 ng/mL) or rising thyroglobulin antibodies with negative imaging studies in the neck. CT chest is favored over MRI chest because it is able to detect small pulmonary metastases [16]. Contrast CT is not necessary for pulmonary metastases but adds to evaluation of metastatic nodes and the thyroid bed. MRI Neck MRI of the neck and mediastinum has the same role as CT.


Thyroid Disease

Thyroid Disease. The performance of MRI for imaging the neck and mediastinum has not been directly compared with CT on large numbers of thyroid cancer patients. MRI has disadvantages of motion artifact in the lower neck from respiration and swallowing and is less sensitive than CT scan for the detection of small pulmonary nodules. Using IV contrast is valuable for detecting recurrence in the surgical bed and assessing suspicious lymph nodes. Octreotide Scan with SPECT or SPECT/CT Chest and Abdomen There is no role for Octreotide scan with SPECT or SPECT/CT chest and abdomen at any stage of evaluation of DTC. Whole-Body Scintigraphy If the US is negative, radioiodine WBS can be performed for suspected recurrence of DTC. WBS may be performed as a first-line investigation in high-risk DTC patients, such as those who initially had macroscopic invasion, gross residual disease, or iodine avid distant metastases. An uptake is sometimes performed to aid in detection of local recurrence and guide dosage of local therapy. I-123 is preferred over I-131 if possible [16], as image quality is higher [40,41]. Variant 8: Suspected recurrence of medullary thyroid cancers. Surveillance for MTC involves monitoring tumor markers, calcitonin, and carcinoembryonic antigen. Imaging of the neck is the preferred initial study. If there is suspicion of recurrence in a body site because of localizing signs or symptoms and elevated tumor markers, the specific body site is imaged. If the patient is asymptomatic, imaging depends on the calcitonin level. Thyroid Disease US Thyroid US of the neck is the first imaging investigation for suspected MTC recurrence and includes evaluation of the thyroid bed and cervical nodes. It can characterize palpable abnormalities in the neck and detect deeper neck masses that are not palpable. Imaging with US of the neck alone is generally adequate with calcitonin levels <150 pg/mL, as disease is usually limited to the neck [51].


Thyroid Disease

Thyroid Disease. Overall, per-person sensitivity is similar to CT with much greater specificity for cervical nodes (sensitivity 75% and specificity 92% for US versus sensitivity 80% and specificity 25% for CT) [52], and detection rate is greater than PET (US finds nodes in 56% of patients versus 32% for PET) [53]. CT Neck CT has greater specificity than US for evaluation of cervical nodes (sensitivity 75% and specificity 92% for US versus sensitivity 80% and specificity 25% for CT) [52]. For calcitonin levels >150 pg/mL, the risk of metastases outside the neck is higher. In these patients, imaging is appropriate, starting with neck and chest CT [54]. Dual- phase CT imaging with and without IV contrast does not provide any additional information. CT Chest For calcitonin levels >150 pg/mL, the risk of metastases outside the neck is higher. CT chest is more sensitive than PET alone for lung nodules (detection rate, 35% for CT versus 20% for PET) and mediastinal nodes (detection rate, 31% for CT versus 20% for PET) [53]. CT should be performed with iodinated contrast in order to better assess for tumor in the surgical bed, vascular encasement, and morphology of small nodal metastases. CT Abdomen For calcitonin levels >150 pg/mL, the risk of metastases outside the neck is higher. Three-phase contrast CT of the liver is an alternative to MRI [54]. MRI Neck MRI has the same role as CT in evaluating sites that are limited on US. The performance of MRI for imaging the neck and mediastinum has not been directly compared with CT on large numbers of thyroid cancer patients. MRI has disadvantages of motion artifact in the lower neck from respiration and swallowing and is less sensitive than CT scan for the detection of small pulmonary nodules. Using IV contrast is valuable for detecting recurrence in the surgical bed and assessing suspicious lymph nodes.


Thyroid Disease

Thyroid Disease. MRI Abdomen MRI of the abdomen is performed for evaluation of liver metastases, and one study reports that it is more sensitive than CT, US, or PET (with a detection rate of 49% versus 44% for CT, 41% for US, and 27% for PET) [53]. A meta-analysis of CT versus MRI for liver metastases of various origins (not MTC) suggests MRI with liver-specific agents is more sensitive than CT [55]. If MRI is used, diffusion-weighted imaging sequences should be included [56]. MRI Complete Spine MRI of the complete spine may be more sensitive than bone scan for bone metastases (100% versus 72% in one study of patients on immunotherapy) [57]. However, another study concluded they were complementary, with equal overall detection rates but bone scintigraphy having the advantage of detecting additional lesions in the extremities (and MRI in the axial skeleton) [53]. Using IV contrast is valuable for detecting bone lesions in this case. FDG-PET/CT Whole Body Medullary cancer is challenging to image with nuclear medicine because it lacks the iodine avidity of DTC while still not being aggressive enough to take up FDG in many cases. FDG-PET/CT has suboptimal detection for MTC in most patients, with 59% sensitivity according to a meta-analysis of 25 studies [58]. However, the sensitivity increases to 75% in patients with more aggressive disease, as indicated by calcitonin levels >1,000 pg/mL and with a calcitonin doubling time <12 months [58-60]. In these patients, FDG-PET/CT may be a first-line study or performed after other imaging studies are negative [61,62]. In countries where the tracer FDOPA (3,4-dihydroxy- 6-18F-fluoro-L-phenylalanine) is available, it should be used in place of FDG as it is more sensitive for MTC [63- 65]. Thyroid Disease Bone Scan Whole Body Bone scan has a role in imaging for patients with symptoms of bone pain with elevated tumor markers and in asymptomatic patients with calcitonin levels >150 pg/mL [16].


Suspected Appendicitis Child

Suspected Appendicitis Child.  Introduction/Background Acute abdominal pain is one of the most common presenting complaints to the emergency department for the pediatric population. While the differential diagnosis for acute abdominal pain in children is broad and includes infectious, inflammatory, musculoskeletal, traumatic, gynecologic, and other etiologies, acute appendicitis is an important differential diagnostic consideration because of the potential need for surgical intervention. Acute appendicitis represents in children [1,2]. Approximately 70,000 children per year in the United States are diagnosed with acute appendicitis, accounting for close to 30% of the total cost of all pediatric general surgical conditions combined [1]. The incidence of appendicitis peaks during adolescence and is uncommon in infants and preschool children and rare in newborns [3]. In spite of its high incidence, the diagnosis of acute appendicitis often presents a challenge, as the classic presenting symptoms of periumbilical pain, anorexia, nausea, vomiting, guarding, and migration of pain to the right lower quadrant (RLQ) are not always elicited and are only moderately reproducible between clinicians [4]. Furthermore, these symptoms are less reliable in the pediatric population, particularly those <5 years of age, who more frequently present with atypical symptoms [1]. As a result, presentation and diagnosis may be delayed, which may contribute to a higher rate of perforated appendicitis in the youngest children [5]. While perforated appendicitis tends to be more common in children than adults [6], morbidity is similar to or lower in children than in adults. The most common treatment of appendicitis is appendectomy. In complicated cases of perforated appendicitis with abscess formation, surgery may follow percutaneous abscess drainage and treatment with broad-spectrum antibiotics [2].


Suspected Appendicitis Child

Suspected Appendicitis Child. Nonoperative treatment of early, uncomplicated appendicitis is increasingly being explored, and imaging plays a role in identifying candidates for nonoperative management [2]. Imaging has been shown to facilitate management and decrease the rate of negative appendectomies in children with suspected acute appendicitis [7-10] and remains a central tool in the diagnosis of pediatric acute appendicitis. Special Imaging Considerations This document aims to provide guidance related to the imaging technique(s) best suited for the diagnosis of acute appendicitis. Importantly, this document does not encompass the appropriate imaging of all potential causes of RLQ quadrant pain. While this guideline emphasizes the role of imaging in the diagnosis of acute appendicitis in children, the initial consideration for imaging is based on clinical assessment. Clinical scoring systems and clinical pathways based upon history, symptoms, physical examination, and laboratory findings have been developed to risk stratify regarding the diagnosis of acute appendicitis and to guide imaging, clinical management, and surgery [11-14]. Two of the more widely used scoring systems are the Alvarado Score and Pediatric Appendicitis Score [13,15]. As primary diagnostic tools, clinical scoring systems have been shown to 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 perform variably well depending on the population and often perform less well than imaging or a combination of scoring and imaging [13,15].


Suspected Appendicitis Child

Suspected Appendicitis Child. The greatest benefit of clinical scoring systems has been to differentiate low-risk patients who do not need surgery and generally do not require imaging from high-risk patients who can be triaged to surgical management, potentially without imaging [16-18]. Imaging should still be considered in cases where clinical judgement is at odds with the high or low risk stratification based on a scoring system. The major role for imaging in the context of clinical scoring systems is in the further evaluation of patients considered to have an intermediate risk of appendicitis [11]. While the specific cut-off values for intermediate risk vary based on the clinical score being used and the desired sensitivity and specificity, the intermediate-risk population is the subgroup that has historical, physical examination, or laboratory findings that do not qualify for either the low- or high-risk groups [13]. US Appendix ultrasound (US) is performed in all potential locations of the appendix with gradual increasing pressure to displace overlying bowel gas and content, which is known as the graded compression technique. Graded compression also serves to bring the appendix closer to the transducer. Appendiceal US can be performed as either a focused examination of the RLQ or as a complete abdominal US. For the purpose of this topic, US abdomen includes dedicated appendiceal study. Accuracy of appendix US varies widely, is operator dependent [19], and may be dependent on patient-specific factors, including obesity [20,21]. The sensitivity and specificity of US for the diagnosis of pediatric acute appendicitis and percentage of equivocal cases varies. US accuracy is optimized in experienced hands and can approach that of CT [22-25]. For this document, it is assumed all procedures are performed and interpreted by an expert.


Suspected Appendicitis Child

Suspected Appendicitis Child. In a large series of 3,799 patients with suspected acute appendicitis, Cundy et al [26] showed 92% visualization of the appendix with 95.5% accuracy, 97% sensitivity, and 95% specificity for the diagnosis of acute appendicitis. As an initial imaging modality for suspected acute appendicitis, US has been shown to have high diagnostic accuracy and to reduce or obviate the need for further imaging without increased complications or unacceptable increases in length of stay [22,26-28]. An important limitation of US is its low sensitivity in the diagnosis of perforated appendicitis [2]. This should be taken in consideration if nonoperative management is considered. CT CT has high sensitivity (~94%) and specificity (~95%) for the diagnosis of acute appendicitis [29]. If the appendix is not visualized, the negative predictive value is similar to a CT with normal visualized appendix [51]. Studies in both children and adults have allowed optimization of CT technique for the diagnosis of acute appendicitis. There is debate about the usefulness of oral contrast because some studies showed no significant increased accuracy, longer time to examination completion, and increased rates of patient emesis [30-32]. Rectal contrast does not increase accuracy compared to CT with intravenous (IV) contrast only [33]. Most CT examinations for appendicitis are performed with standard technique and coverage for imaging the abdomen and pelvis. Some centers have had success decreasing CT exposure parameters without compromising diagnostic performance [34,35] for acute appendicitis. Other retrospective studies in both adult and pediatric populations have shown that a focused CT from L2 or L3 or based on height-adjusted distance from the umbilicus through the pubis symphysis is sufficient to diagnose acute appendicitis and identify most alternative diagnoses [36,37]. There are no studies that compare unenhanced and contrast-enhanced CT for diagnosis of acute appendicitis.


Suspected Appendicitis Child

Suspected Appendicitis Child. A limited number of retrospective studies of pediatric cohorts imaged without IV contrast have shown rates of visualization of the appendix similar to CT performed with IV contrast as well as high sensitivity and specificity for the diagnosis of appendicitis [1,2]. Potential limitations of unenhanced CT include decreased sensitivity and incomplete characterization of complicated appendicitis (eg, perforation and abscess formation) and possibly lower sensitivity for alternative diagnoses [38,39]. There are no data to suggest that CT with and without IV contrast has better diagnostic performance for acute appendicitis or alternative diagnoses than a single phase (CT with or CT without IV contrast) examination. Furthermore, CT with and without IV contrast approximately doubles radiation exposure to the patient. Radiography Abdomen Most studies have shown that in patients stratified as low risk (which varies per study and is based on the system used), imaging for acute appendicitis is not required, and other causes of abdominopelvic pain should be sought [13,16,17,48-50]. Radiographs may identify alternative causes of pain, such as constipation or lower lobe pneumonia [51]. US Abdomen RLQ Most studies have shown that in patients stratified as low risk (which varies per study and is based on the system used), imaging for acute appendicitis is not required, and other causes of abdominopelvic pain should be sought [13,16,17,48-50]. US Abdomen Most studies have shown that in patients stratified as low risk (which varies per study and is based on the system used), imaging for acute appendicitis is not required, and other causes of abdominopelvic pain should be sought [13,16,17,48-50]. US Pelvis Most studies have shown that in patients stratified as low risk (which varies per study and is based on the system used), imaging for acute appendicitis is not required, and other causes of abdominopelvic pain should be sought [13,16,17,48-50].


Suspected Appendicitis Child

Suspected Appendicitis Child. Pelvic US may identify other causes of pain in girls but there are no data regarding its performance as a first-line imaging modality for acute appendicitis [52]. CT Abdomen and Pelvis In a retrospective study of children who underwent CT of the abdomen and pelvis for suspected acute appendicitis, Kim et al [50] found that no patient categorized as low risk by the Pediatric Appendicitis Score had a positive CT. Similarly, based on retrospective study of a mixed population of children and adults who underwent CT, McKay and Shepard [53] showed that the Alvarado score could rule out appendicitis in low-risk patients with 96% sensitivity. Alternative causes of abdominopelvic pain, which have been described to occur at rates between 7% and 25%, may be identified by CT [54,55]. There are no studies that compare unenhanced and contrast-enhanced CT for diagnosis of acute appendicitis [38,39]. MRI Abdomen and Pelvis Most studies have shown that in patients stratified as low risk (which varies per study and is based on the system used), imaging for acute appendicitis is not required, and other causes of abdominopelvic pain should be sought [13,16,17,48-50]. Alternative causes of abdominopelvic pain, which occurred at a rate of 20% in a study of MRI as the primary imaging modality for suspected acute appendicitis, may be identified by MRI [55]. Radiography Abdomen Radiographs are neither sensitive nor specific for the diagnosis of acute appendicitis but may identify alternative causes of pain [51]. US Abdomen There are no specific data regarding the relative performance of a focused RLQ US versus a complete abdominal US in intermediate-risk patients. US Pelvis There are no data specific to the use of pelvic US only in children with intermediate clinical risk for acute appendicitis. Pelvic US may be part of a complete evaluation for abdominopelvic pain in peri- or postmenarchal girls [52].


Suspected Appendicitis Child

Suspected Appendicitis Child. CT Abdomen and Pelvis CT of the abdomen and pelvis has been shown to provide diagnostic benefit in a mixed population of children and adults with intermediate clinical risk for acute appendicitis where the examination had 90% sensitivity and 95% specificity for acute appendicitis [53]. Because CT covers more anatomic territory than a limited RLQ US, it may identify alternative causes of abdominopelvic pain [54,55]. There are no studies that compare unenhanced and contrast-enhanced CT for diagnosis of acute appendicitis [38,39]. MRI Abdomen and Pelvis Given its high sensitivity and specificity for acute appendicitis, MRI may be indicated in children with an intermediate clinical risk for acute appendicitis [40,41,43]. Similar to CT, the greater anatomic coverage of MRI (versus US) may identify alternative causes of abdominopelvic pain [54,55]. Variant 3: Child. Suspected acute appendicitis, high clinical risk. Initial imaging. Risk stratification for acute appendicitis can be achieved based on overall subjective assessment or use of published scoring systems. The patient-specific likelihood of acute appendicitis among patients classified as high risk varies across the range of high-risk scores and varies between published studies [56]. Approaches to high-risk patients vary in the literature, with some studies using imaging to confirm the diagnosis of appendicitis [49] and other studies advocating surgical intervention without imaging based on a demonstrated high accuracy of the scoring system in their practice [13,17,18,48,57]. Radiography Abdomen Radiographs are neither sensitive nor specific for a diagnosis of acute appendicitis but may aid in terms of excluding complications of acute appendicitis, such as bowel obstruction or gross perforation [51]. US Abdomen RLQ There is no evidence to support routine US in all patients considered high risk for acute appendicitis.


Suspected Appendicitis Child

Suspected Appendicitis Child. However, US could be used to confirm the diagnosis of acute appendicitis in this population and to exclude other processes US Abdomen US may be performed in selected high-risk patients to confirm the diagnosis of appendicitis, but US is likely not needed in all high-risk patients, and false-negative results are more common in this population [58]. US Pelvis There are no data regarding the performance of pelvic US as a first-line imaging modality for acute appendicitis. In peri- or postmenarchal girls, a pelvic US may identify alternative causes of pelvic pain [52]. CT Abdomen and Pelvis There is no evidence to support routine use of CT of the abdomen and pelvis or of focused CT in high-risk patients. Based on high sensitivity and specificity, CT could be used to confirm the diagnosis of acute appendicitis in these patients and to exclude other processes that clinically mimic appendicitis. Tan et al [14] showed that in a population of adult and adolescent patients, the positive likelihood ratio for CT was no different from clinical scoring in patients with a high-risk clinical score, suggesting no diagnostic benefit of CT in this context. There are no studies that compare unenhanced and contrast-enhanced CT for diagnosis of acute appendicitis [38,39]. MRI Abdomen and Pelvis There is no evidence to support routine use of MRI in high-risk patients. Based on high sensitivity and specificity that is similar to CT, MRI could be used to confirm the diagnosis of acute appendicitis in high-risk patients and to exclude other processes that clinically mimic appendicitis. However, the diagnostic benefit of MRI in this context has not been demonstrated. Variant 4: Child. Suspected acute appendicitis, equivocal or nondiagnostic right lower quadrant ultrasound. Next imaging study. The definition of an equivocal or nondiagnostic US for acute appendicitis varies widely in the literature, and careful definition of this category has major implications on imaging utilization [22,59,60].


Suspected Appendicitis Child

Suspected Appendicitis Child. Some consider nonvisualization of the appendix as an equivocal result [40,61]. However, in several retrospective studies, an appendiceal US in which the appendix is not visualized and no inflammatory findings are present in the RLQ has high negative predictive value [3,62-64]. In this context, further imaging is unlikely to be contributory unless there is discordance between the clinical picture and the negative US result [65]. Further imaging, however, is contributory after equivocal US examinations in which the appendix is either visualized or not visualized, and there are findings that could reflect appendicitis. In one study, appendicitis was present in 26% of patients who met this criteria [3]. While there is good evidence regarding secondary imaging modalities following an equivocal US, there is also evidence of the benefit of repeat clinical assessment in these cases, which can obviate further imaging at the expense of delay in diagnosis and the risk associated with extending the hospital visit [10,66]. Schuh et al [67] in a prospective study found that of 123 patients with an initially equivocal US, acute appendicitis could be correctly ruled out clinically in 59% based on reassessment without further imaging. Radiography Abdomen Given the limited sensitivity and specificity, a radiograph is unlikely to diagnose acute appendicitis in patients with an initial equivocal or nondiagnostic appendiceal US [51]. Radiographs may identify an alternative cause of pain. US Abdomen RLQ Repeating a US examination after an initially equivocal result increases sensitivity for acute appendicitis. Schuh et al [67] showed that repeat US could make a diagnosis in 55% of cases with persistent clinical concern for acute appendicitis after an initially equivocal US. This final diagnosis rate, however, is lower than what has been reported with both CT and MRI.


Suspected Appendicitis Child

Suspected Appendicitis Child. US Abdomen There are no specific data related to whether a repeat focused RLQ US or a completed abdominal US is more effective in the setting of an initial equivocal US. There are no studies that compare unenhanced and contrast-enhanced CT for diagnosis of acute appendicitis [38,39]. MRI Abdomen and Pelvis MRI performed following equivocal or nondiagnostic appendix US has similar sensitivity and specificity to CT with 100% sensitivity and 96% specificity demonstrated by Herliczek et al [41,71]. In a clinical pathway with US as the initial modality and MRI for problem solving, Epifanio et al [48] demonstrated MRI to add diagnostic benefit in the small subset of cases that remained indeterminate after US. The overall sensitivity and specificity of the described pathway were 96% and 100%, respectively. Importantly, Aspelund et al [72] showed no difference in clinical outcomes following a shift from CT as the primary imaging modality for acute appendicitis to US with MRI for equivocal cases. Regarding perforated appendicitis, Dillman et al [40] showed subsequent MRI to have similar sensitivity and specificity to CT for diagnosis of perforation in patients with an initially equivocal or nondiagnostic RLQ US. It should be noted, however, that the total number of cases of perforation in this study was small (10 in the MR group and 4 in the CT group). Variant 5: Child. Suspected acute appendicitis with clinical suspicion or initial imaging suggestive of complication (eg, abscess, bowel obstruction). Next imaging study. Complicated appendicitis, generally a result of perforation, occurs at a frequency of approximately 30% in the pediatric population and has implications for clinical care [73]. There is debate in the literature regarding optimal care for patients with perforated appendicitis, which can range from antibiotic therapy with delayed appendectomy to interventional drainage to surgical intervention.


Suspected Appendicitis Child

Suspected Appendicitis Child. Radiography Abdomen Radiographs may identify possible complications of acute appendicitis by identifying bowel obstruction or gross perforation. Radiographs, however, have limited sensitivity and specificity for the diagnosis of acute appendicitis as a cause of the complication [51]. US Abdomen RLQ In general, US has been shown to have limited accuracy in the distinction of perforated from nonperforated acute appendicitis [2]. While US can identify RLQ fluid collections/abscesses and dilated bowel loops, the limited field of view may be inadequate to fully assess complications of appendiceal perforation and thereby guide clinical management. US Abdomen The greater anatomic coverage of a full abdominal US (versus an RLQ US) may identify additional findings of complicated acute appendicitis outside of the RLQ, but the small image field of view is still limiting in terms of overall assessment of complications. US Pelvis Focused US of the pelvis is limited in terms of overall assessment of complicated acute appendicitis secondary to its small scope of imaging and field of view. CT Abdomen and Pelvis CT of the abdomen and pelvis with IV contrast, with or without oral contrast, provides a broad field of view for assessment of complications of acute appendicitis, including perforation, abscess, and bowel obstruction. Focused CT will likely be sufficient to characterize complicated appendicitis in the lower abdomen and pelvis; however, the limited coverage may not permit characterization of complications if they extend into the upper abdomen (eg, perisplenic or perihepatic collections). However, this has not been specifically studied. There are no studies that compare unenhanced and contrast-enhanced CT for diagnosis of acute appendicitis. Unenhanced CT may be limited in its ability to characterize complicated appendicitis (eg, perforation and abscess formation) [38,39].


Imaging of Facial Trauma Following Primary Survey.  aMallinckrodt Institute of Radiology, Saint Louis, Missouri. bPanel Chair, University of Iowa Hospitals and Clinics, Iowa City, Iowa. cPanel Vice-Chair, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts. dFroedtert Memorial Lutheran Hospital Medical College of Wisconsin, Milwaukee, Wisconsin. eEmory University, Atlanta, Georgia; American Association for the Surgery of Trauma. fMontefiore Medical Center, Bronx, New York. gUniversity of Rochester Medical Center, Rochester, New York; American Academy of Otolaryngology-Head and Neck Surgery. hHouston Methodist Hospital, Houston, Texas. iUniversity of Texas Health Science Center, Houston, Texas. jThe University of Texas MD Anderson Cancer Center, Houston, Texas. kUniversity of Illinois at Chicago, Chicago, Illinois; University of Chicago, Chicago, Illinois; American Society of Plastic Surgeons. lNew York University Langone Health, New York, New York. mMetroHealth Medical Center, Cleveland, Ohio. nMayo Clinic Arizona, Phoenix, Arizona. oUniversity of Iowa Carver College of Medicine, Iowa City, Iowa, Primary care physician. pThe University of Texas MD Anderson Cancer Center, Houston, Texas; Commission on Nuclear Medicine and Molecular Imaging. qGeorge Washington University Hospital, Washington, District of Columbia. rUniversity of Colorado Denver, Denver, Colorado. sSpecialty Chair, Atlanta VA Health Care System and Emory University, Atlanta, Georgia. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org OR Discussion of Procedures by Variant Variant 1: Tenderness to palpation or contusion or edema over frontal bone.


Imaging of Facial Trauma Following Primary Survey. Suspect frontal bone injury. Initial imaging following primary survey. Representing 5% to 15% of all facial fractures, frontal bone fractures are often the result of high-energy blunt trauma, such as motor vehicle collisions, assaults, and significant falls [30]. Thick cortical bone comprises the anterior table of the frontal sinus, allowing it to withstand up to 1,000 kg of force before fracturing, rendering it the sturdiest bone in the face [31]. In contrast, the posterior table of the frontal sinus, separating the sinus from the anterior cranial fossa, is relatively easily fractured secondary to its thin, delicate nature. One-third of injuries are isolated to the anterior table, whereas two-thirds involve both anterior and posterior tables [31]. Injuries along the inferomedial aspect of the frontal sinus and anterior ethmoids may cause occlusion of the nasofrontal duct leading to potential mucocele formation and possibly osteomyelitis [9,15,22,31-33]. Likewise, fractures through the medial aspect of the frontal sinus floor typically involve the cribriform plate and fovea ethmoidalis and may result in cerebrospinal fluid (CSF) leak or chronic sinusitis. Fractures through the lateral part of the frontal sinus floor may involve the orbital roof. Imaging of Facial Trauma Following Primary Survey CT Maxillofacial Multidetector CT (MDCT) is useful in diagnosing maxillofacial injuries [2,30,31,37-43]. MDCT offers superb delineation of osseous and soft-tissue structures. CT provides high image resolution with thin-section acquisitions allowing for the detection of subtle nondisplaced fractures of the facial skeleton. Also, CT offers multiplanar and 3-D image reconstructions, allowing for better characterization of complex fractures. In particular, many surgeons find the 3-D reformations to be critical in their preoperative planning [13,15,21,39,41,44-46]. CT allows for a faster acquisition time than other modalities such as radiography and MRI.


Imaging of Facial Trauma Following Primary Survey. Also, it is less reliant on patient positioning than radiography. CT is typically the first-line of imaging to identify penetrating foreign bodies and the subsequent determination of their trajectory and extent of the injury [47,48]. A novel volume visualization tool, cinematic rendering, is a promising technique to illustrate maxillofacial fractures [41]. CT with IV contrast does not aid in detection of osseous facial injury. associated cervical spine injuries [19]. Imaging of Facial Trauma Following Primary Survey Radiography Skull CT has replaced radiographs for the initial imaging evaluation of suspected frontal bone injury because radiographs cannot characterize the full extent of fractures, detect nasofrontal duct involvement, and ascertain intracranial pathology [30,59]. Approximately 3% of radiographs that did not detect skull fracture had fractures visible on CT in one study. In the group in which radiographs failed to detect a skull fracture, half of the group eventually developed an epidural hematoma [60]. Radiographs may be useful in identifying and determining the location of foreign bodies in the maxillofacial region [50]. High-velocity maxillofacial trauma and penetrating neck trauma are the most common causes of traumatic vascular injuries. Identification and treatment of these injuries should be swift because irreversible neurologic damage or death may occur. Although blunt cerebrovascular injuries (BCVI) are uncommon in maxillofacial trauma, exclusion of these injuries is necessary when clinical suspicion is present [21]. The excellent negative predictive value and high sensitivity of the revised Denver criteria make them an excellent screening tool for BCVI [61]. Using these criteria, blunt trauma patients with particular signs and symptoms of BCVI or risk factors for BCVI should undergo cerebrovascular imaging. Complex skull fractures or scalp degloving are both risk factors for BCVI, which may occur in frontal injuries.


Imaging of Facial Trauma Following Primary Survey. Occult neurovascular injury, carotid-cavernous fistula, or carotid transection can occur with severe facial fractures [62,63]. A penetration trajectory, vessel wall hematoma, infiltration of perivascular fat, or foreign bodies <5 mm from a vessel wall should raise suspicion of vascular injury requiring vascular imaging [64,65]. CT angiography (CTA) has been recommended over digital subtraction angiography for initial vascular evaluation because of its short acquisition time and low complication rate [21,29]. CTA detects almost all clinically relevant blunt cervical arterial injuries [29,66]. As stated above, BCVI, although uncommon in maxillofacial trauma, carries significant morbidity and mortality if not identified and treated early. Therefore, the exclusion of these injuries is necessary in the correct clinical context. Although MR angiography (MRA) is inferior to conventional arteriography, it is considered equivalent to CTA in BCVI. Similar to CTA, MRA does distinguish almost all clinically significant cervical arterial injuries [29,66]. However, MRA without IV contrast in the neck may be limited because of artifacts and limited resolution. Subtle vascular injuries such as wall irregularity and thickening and mild luminal irregularity can be difficult to detect [67]. Also, MRA with or without IV contrast is time-consuming, making it challenging to use in an acute trauma setting. Some debate exists as to whether CTA is superior to MRA in BCVI. One study found CTA to be superior [68], whereas another found them to be equivalent [29,69]. Virtual arteriograms can be created without IV contrast using time-of-flight or phase-contrast sequences. Nevertheless, pseudoaneurysms or subtle stenoses are more easily detected by administering contrast intravenously using 3-D time-of-flight imaging.


Imaging of Facial Trauma Following Primary Survey. Arteriography Cervicocerebral Angiography of the head and neck may logically follow identification of specific bony or soft tissue injuries but is not useful as the initial imaging modality to identify frontal bone injury. Angiography is used as a problem-solving Imaging of Facial Trauma Following Primary Survey As stated above, BCVI, although uncommon in maxillofacial trauma, carries significant morbidity and mortality if not identified and treated early. Therefore, the exclusion of these injuries is necessary in the correct clinical context. Despite improvements in CTA and MRA, the reference standard for identifying cervical arterial injury remains arteriography because of its ability to detect low-grade injuries missed on other modalities [29,70-72]. However, CTA or MRA is generally utilized over arteriography currently, secondary to the 1% to 2% risk of meaningful complications such as stroke and dissection [29]. addresses the role of imaging in the setting of head trauma. CT with IV contrast does not aid in detection of head injury. MRI Maxillofacial There is no relevant literature to support the use of MRI of the face in the initial imaging evaluation of suspected midface injury. However, in patients with cranial nerve deficits not explained or incompletely characterized by CT, MRI can be a useful supplement [31]. In particular, some Le Fort II injuries can disrupt the infraorbital nerve (V2), leading to anesthesia of the upper teeth, gingiva, upper lip, and lateral aspects of the nose [15,32,80]. Zygomatic maxillary complex fractures are often associated with infraorbital nerve (V2) deficits as well [4,79]. In naso-orbital- ethmoid fractures, olfactory nerve injury often occurs. Because of its superior soft-tissue contrast and multiplanar capabilities, MRI may be helpful in the detection of CSF leak from a skull base fracture. High resolution heavily T2-weighted images are useful in the evaluation of the olfactory nerve and for potential CSF leaks.


Imaging of Facial Trauma Following Primary Survey. MRI aids in diagnosing the contents that have herniated through a defect in skull base injuries [49]. These skull base injuries can occur in naso-orbital-ethmoid fractures [31]. Also, MRI is superior to CT for detecting small pieces of asphalt, which could occur as facial foreign bodies [50]. MRI with IV contrast is not useful in detection of facial injury. Imaging of Facial Trauma Following Primary Survey associated cervical spine injuries [19]. Radiography Paranasal Sinuses For injuries of the midface, CT has largely replaced radiographs [15,30]. The limitations with radiographs are primarily related to inaccuracies, especially with small or fine structures, associated with the superimposition of adjacent anatomic structures and the lack of technical skill resulting from disuse and a lack of training [2]. In one study, radiologists missed 12% of maxillofacial fractures on radiographs compared with CT [81]. When combined with an appropriate physical examination, the Waters, Caldwell, and submentovertex views can provide sufficient information to verify the clinical diagnosis of a zygomaticomaxillary complex fracture. Still, both patient positioning and technological experience are essential [15]. Radiographs may be useful in identifying and determining the location of foreign bodies in the maxillofacial region [50]. High-velocity maxillofacial trauma and penetrating neck trauma are the most common causes of traumatic vascular injuries. Identification and treatment of these injuries should be swift because irreversible neurologic damage or death may occur. Occult neurovascular injury, carotid-cavernous fistula, or carotid transection can occur with severe facial fractures [62,63]. Although BCVI are uncommon in maxillofacial trauma, exclusion of these injuries is necessary when clinical suspicion is present [21]. The excellent negative predictive value and high sensitivity of the revised Denver criteria make them an excellent screening tool for BCVI [61].


Imaging of Facial Trauma Following Primary Survey. Using these criteria, blunt trauma patients with particular signs and symptoms of BCVI or risk factors for BCVI should undergo cerebrovascular imaging. Le Fort II and Le Fort III fractures are both risk factors for BCVI. Also, the Eastern Association for the Surgery of Trauma currently recommends screening all patients with Le Fort II or III facial fractures for the presence of BCVI [82]. One study based on an analysis of 4,398 patients recommended screening for BCVI in Le Fort I facial fractures [17]. A penetration trajectory, vessel wall hematoma, infiltration of perivascular fat, or foreign bodies <5 mm from a vessel wall should raise suspicion of vascular injury requiring vascular imaging [64,65]. CTA has been recommended over digital subtraction angiography for initial vascular evaluation because of its short acquisition time and low complication rate [21,29]. CTA detects almost all clinically relevant blunt cervical arterial injuries [29,66]. MRA Head and Neck MRA of the head and neck may logically follow identification of specific bony or soft-tissue injuries but is not useful as the initial imaging modality to identify midface injury. Guidance on the imaging of vascular injuries in Imaging of Facial Trauma Following Primary Survey As stated above, BCVI, although uncommon in maxillofacial trauma, carries significant morbidity and mortality if not identified and treated early. Therefore, the exclusion of these injuries is necessary in the correct clinical context. Although MRA is inferior to conventional arteriography, it is considered equivalent to CTA in BCVI. Similar to CTA, MRA does distinguish almost all clinically significant cervical arterial injuries [29,66]. However, MRA without IV contrast in the neck may be limited because of artifacts and limited resolution. Subtle vascular injuries such as wall irregularity and thickening and mild luminal irregularity can be difficult to detect [67].


Imaging of Facial Trauma Following Primary Survey. Also, MRA with or without IV contrast is time-consuming, making it challenging to use in an acute trauma setting. Some debate exists as to whether CTA is superior to MRA in BCVI. One study found CTA to be superior [68], whereas another found them to be equivalent [29,69]. Virtual arteriograms can be created without IV contrast using time-of-flight or phase-contrast sequences. Nevertheless, pseudoaneurysms or subtle stenoses are more easily detected by administering contrast intravenously using 3-D time-of-flight imaging. As stated above, BCVI, although uncommon in maxillofacial trauma, carries significant morbidity and mortality if not identified and treated early. Therefore, the exclusion of these injuries is necessary in the correct clinical context. Despite improvements in CTA and MRA, the reference standard for identifying cervical arterial injury remains arteriography because of its ability to detect low-grade injuries missed on other modalities [29,70-72]. However, CTA or MRA is generally utilized over arteriography currently, secondary to the 1% to 2% risk of meaningful complications such as stroke and dissection [29]. Radiography Chest There is no relevant literature to support the use of chest radiography in the initial imaging evaluation of suspected midface injury. However, a chest radiograph may be warranted to exclude tooth aspiration if there is a tooth that is absent [46,83]. A physician or surgeon should remove an avulsed tooth in the airway because of the risk of developing obstructive pneumonia [9]. Imaging of Facial Trauma Following Primary Survey cosmetic deformity and nasal obstruction [32]. In particular, a fracture involving the nasal cartilage may cause a septal hematoma leading to cartilage necrosis or resorption, and if untreated, a subsequent saddle nose deformity. US Maxillofacial Ultrasound (US) is typically not the first-line imaging test for evaluation of nasal injuries.


Imaging of Facial Trauma Following Primary Survey. However, researchers have investigated whether US might be useful in this scenario. Research using US has revealed a very high accuracy with sensitivity ranging from 90% to 100%, a specificity of 98% to 100%, and high predictive values [38,85,86]. This is particularly true of isolated nasal bone fractures [87,88]. According to two reports, US better detects nondepressed fractures of the nasal bridge and anterior septal cartilage deviation than CT [85,86]. A conductor- assisted nasal US technique detected nasal fractures, with 100% sensitivity and 89% specificity, 96% positive predictive value, and 100% negative predictive value [89]. Another study revealed that US is a reliable diagnostic tool for estimating the time of nasal bone fracture [90]. Radiography Paranasal Sinuses Nasal radiographs have limited diagnostic value in the evaluation of nasal trauma. According to several studies, the diagnostic accuracy for radiographs to detect nasal bone fractures ranges from 53% to 82% [91-93]. Radiographs do not considerably alter the diagnosis or management of nasal fractures [94]. CT Head There is no relevant literature to support the use of CT of the head in the initial imaging evaluation of suspected nasal bone injury. CT Maxillofacial MDCT is useful in diagnosing maxillofacial injuries [2,30,31,37-43]. MDCT offers superb delineation of osseous and soft-tissue structures. CT provides high image resolution with thin-section acquisitions allowing for the detection of subtle nondisplaced fractures of the facial skeleton. Also, CT offers multiplanar and 3-D image reconstructions, allowing for better characterization of complex fractures. In particular, many surgeons find the 3- D reformations afforded by CT to be critical in their preoperative planning [13,15,21,39,41,44-46]. In complex nasal injuries and other associated facial fractures, CT can fully characterize the extent of injuries and detect any additional facial injuries [30].


Imaging of Facial Trauma Following Primary Survey. When compared with radiographs, CT is more sensitive in confirming the clinical suspicion of nasal bone fracture [93]. Several classification systems exist for nasal bone fractures, and one classification system created by Rhee et al [95] relies solely on CT to determine the degree of septal deviation. CT allows for a quicker acquisition time compared with other modalities such as radiography and MRI. Also, it is less reliant on patient positioning than radiography. CT is useful as the first-line of imaging to identify penetrating foreign bodies and the subsequent determination of their trajectory and extent of the injury [47,48]. A novel volume visualization tool, cinematic rendering, is a promising technique to illustrate maxillofacial fractures [41]. CT with IV contrast does not aid in detection of facial injury. MRI Maxillofacial There is no relevant literature to support the use of MRI of the face in the initial imaging evaluation of suspected nasal bone injury. Variant 4: Trismus or malocclusion or gingival hemorrhage or mucosal hemorrhage or loose teeth or fractured teeth or displaced teeth. Suspect mandibular injury. Initial imaging following primary survey. Fractures of the mandible comprise a large proportion of facial fractures because it is vulnerable to low-energy forces. In the setting of assaults and ballistic trauma, the mandible is the most common maxillofacial fracture site [6,96]. Mandibular fractures are classified according to the degree of comminution, location, and the presence of displaced fragments [22]. The mandible is a U-shaped bone forming an incomplete ring that articulates with the calvaria via the temporomandibular joints. Secondary to this ring-like configuration, two separate fractures occur in the mandible in approximately 67% of cases [22,31]. Thus, a second fracture must be sought and excluded after the first fracture is detected.


Imaging of Facial Trauma Following Primary Survey. A frequent pattern with two distinct fractures is a mandibular angle or subcondylar fracture with a contralateral parasymphyseal fracture. Another critical pattern, a flail mandible, consists of bilateral subcondylar fractures with a symphyseal fracture. In addition to these osseous injuries, fractures of the mandible may damage the inferior alveolar nerve because they extend through the mandibular canal. Beyond the mandible, approximately 20% to 40% of patients with mandibular fractures have further injuries [97]. CT Maxillofacial MDCT is useful in diagnosing maxillofacial injuries [2,30,31,37-43]. MDCT offers superb delineation of osseous and soft-tissue structures. CT provides high image resolution with thin-section acquisitions allowing for the detection of subtle nondisplaced fractures of the facial skeleton. CT is superior to radiography for the evaluation of mandibular fractures [96]. Nearly 100% sensitive with an improved interobserver agreement, CT with multiplanar reformations is proficient in detecting fractures of the mandible [31,99]. This is especially true of posterior mandibular fractures [3,100]. According to one study, more fractures are identified on CT when there is no fracture visible on orthopantomogram (OPG) [99]. CT is beneficial when evaluating ramus or condyle fractures, because the degree of displacement in these areas can be subtle [101]. CT is especially useful in identifying comminution and displacement of mandibular fractures. These are critical findings because they result in a change in surgical management [100,102,103]. Also, CT offers both multiplanar and 3-D image reconstructions, which allow for better characterization of complex fractures. In particular, many surgeons find the 3-D reformations afforded by CT to be critical in their preoperative planning [13,15,21,39,41,44-46]. CT allows for a faster acquisition time than other modalities such as radiography and MRI.


Imaging of Facial Trauma Following Primary Survey. Also, it is less reliant on patient positioning than radiography. CT is typically the first-line of imaging to identify penetrating foreign bodies and the subsequent determination of their trajectory and extent of the injury [47,48]. A novel volume visualization tool, cinematic rendering, is a promising technique to illustrate mandibular fractures [41]. CT with IV contrast does not aid in detection of facial injury. MRI Maxillofacial In rare instances, some reports have advocated for MRI in the acute setting to diagnose temporomandibular joint disc morphology and position in certain condylar fractures [2,104,105]. Also, in patients with cranial nerve deficits not explained or incompletely characterized by CT, MRI can be a useful supplement [31]. In particular, fractures through the mandibular canal may damage the inferior alveolar nerve as it travels through the mandibular canal. Damage to the inferior alveolar nerve may result in anesthesia of the ipsilateral lower lip, chin, anterior tongue, and mandibular teeth. Also, MRI is superior to CT for detecting small pieces of asphalt, which could occur as facial foreign bodies [50]. MRI with IV contrast is not useful in detection of facial injury. Radiography Mandible In patients with a low clinical suspicion of injury, an OPG (panoramic radiograph) or mandibular series consisting of Towne, bilateral lateral oblique, and lateral views may be obtained to evaluate for mandibular fractures. With a sensitivity of 86% to 92%, OPG has better sensitivity for detecting simple mandibular fractures than a standard 4- view mandibular imaging series [31,101,102,106]. Specifically, an OPG demonstrated a sensitivity of 92% in detecting a mandibular fracture in contrast with 66% with a mandibular series [106].


Imaging of Facial Trauma Following Primary Survey. A mandibular series possess several disadvantages compared with an OPG such as superimposition of osseous structures, difficulty in placing the film perpendicular to the fracture, and presence of confusing spatial relationships. A mandibular series does not require the patient to be upright, remain motionless for an extend period, or cervical spine clearance like an OPG [31]. Although isolated mandibular fractures have often been accurately diagnosed using radiography techniques, notable limitations include fractures of the mandible condyle and subcondylar fractures having anterior 14 Imaging of Facial Trauma Following Primary Survey displacement, both of which are more easily demonstrated on CT [107,108]. In addition, an OPG can miss both nondisplaced and minimally displaced anterior fractures when there is overlap with the cervical spine [99,109]. A complex fracture may be mistaken for an isolated fracture if OPG is used initially [42]. An OPG can better visualize dental root fractures compared with CT, particularly when the fracture is located at an angle [31]. The use of OPG and mandibular series radiographs has become less favorable in emergency and trauma care settings [110]. Despite this fact, some authors have used radiographs for creating scoring systems for mandibular fractures for an objective and standardized assessment for the degree of severity of mandibular fractures [111]. associated cervical spine injuries [19]. Imaging of Facial Trauma Following Primary Survey High-velocity maxillofacial trauma and penetrating neck trauma are the most common causes of traumatic vascular injuries. Identification and treatment of these injuries should be swift because irreversible neurologic damage or death may occur. Occult neurovascular injury, carotid-cavernous fistula, or carotid transection can occur with severe facial fractures [62,63].


Imaging of Facial Trauma Following Primary Survey. Although BCVI are uncommon in maxillofacial trauma, exclusion of these injuries is necessary when clinical suspicion is present [21]. The excellent negative predictive value and high sensitivity of the revised Denver criteria make them an excellent screening tool for BCVI [61]. As a risk factor for BCVI, condylar and extracapsular subcondylar fractures should heighten suspicion for concomitant BCVI [9,112]. The data support a force transmission mechanism of injury in addition to direct damage from bony fragments [72,105]. A penetration trajectory, vessel wall hematoma, infiltration of perivascular fat, or foreign bodies <5 mm from a vessel wall should raise suspicion of vascular injury requiring vascular imaging [64,65]. CTA has been recommended over digital subtraction angiography for initial vascular evaluation because of its short acquisition time and low complication rate [21,29]. CTA detects almost all clinically relevant blunt cervical arterial injuries [29,66]. As stated above, BCVI, although uncommon in maxillofacial trauma, carries significant morbidity and mortality if not identified and treated early. Therefore, the exclusion of these injuries is necessary in the correct clinical context. Regarding mandibular injuries, condylar and extracapsular subcondylar fractures should heighten suspicion for concomitant BCVI [9,112]. The data support a force transmission mechanism of injury in addition to direct damage from bony fragments [72,105]. Although MRA is inferior to conventional arteriography, it is considered equivalent to CTA in the setting of BCVI. Similar to CTA, MRA does distinguish almost all clinically significant cervical arterial injuries [29,66]. However, MRA without IV contrast in the neck may be limited because of artifacts and limited resolution. Subtle vascular injuries such as wall irregularity and thickening and mild luminal irregularity can be difficult to detect [67].


Neck Mass Adenopathy

Neck Mass Adenopathy.  The American Academy of Otolaryngology-Head and Neck Surgery recently created clinical guidelines for the evaluation of a neck mass in adults [14], emphasizing the importance of timely diagnosis. They issued a strong recommendation for contrast-enhanced neck CT or contrast-enhanced neck MRI for patients with a neck mass deemed at risk for malignancy. In their treatment flow chart, imaging was considered in parallel with fine-needle aspiration of the palpable mass or node for timing of diagnostic evaluation. Ultrasound (US) was considered an option for initial imaging in suspected thyroid or salivary masses or as an adjunct to expedite sampling. Discussion of Procedures by Variant Variant 1: Nonpulsatile neck mass(es). Not parotid region or thyroid. Initial imaging. Cross-sectional imaging with CT or MRI allows for precise localization of the palpable finding. Both CT and MRI can accurately assess tumors and inflammation, and CT and MRI are considered equally effective studies for clinical oncologic evaluation [14,19]. Intravenous (IV) contrast is essential for detecting neck abscesses, especially those that are intramuscular [20-22]. Contrast-enhanced imaging is helpful for identifying nodal necrosis and can help guide the search for primary tumor [23,24]. Contrast also helps to clarify primary tumor within the upper aerodigestive tract and the relationship of neck masses to the major vessels of the neck. 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 Neck Mass/Adenopathy


Neck Mass Adenopathy

Neck Mass Adenopathy. CT Neck Contrast-enhanced CT has the advantage of superior spatial resolution and is the preferred initial imaging modality for a palpable nonpulsatile neck mass in an adult, particularly considering the risk of head and neck cancer [14,19,25,26]. The presence and distribution of abnormal lymph nodes may be helpful when refining the differential as a reactive or malignant process and in guiding the search for an unknown primary malignancy [19,27,28]. Dual-phase CT imaging (without and with IV contrast) is not usually necessary. CT performed only without IV contrast may be helpful in some cases. CTA Neck There is no evidence to support the use of CT angiography (CTA) for evaluation of a nonpulsatile neck mass. MRI Neck The primary advantage of MRI is improved soft-tissue intrinsic contrast. Intrinsic T1-hyperintensity and fat suppression techniques can confirm fat-containing lesions in the neck [28]. Diffusion-weighted imaging can identify soft-tissue abscess [34]. Apparent diffusion coefficient values also have been proposed as a discriminator between benign and malignant nodal disease in the neck [34-36] and with intravoxel incoherent motion features for both primary and nodal disease [37]; however, histology is needed to confirm any suspected malignancy [13,14,19]. Motion artifact may be a significant issue, particularly for patients who have difficulty managing secretions that are due to neck disease. MRI performed without IV contrast may be helpful in some cases. MRA Neck There is no evidence to support the use of MR angiography (MRA) for evaluation of a nonpulsatile neck mass. US Neck The overall use of neck US in the United States has lagged behind the use of US in Europe and Southeast Asia, which is due, in part, to greater accessibility of CT and MRI in the United States [38-40]. For discrete cystic lesions of the neck, US may suffice to characterize a lesion prior to definitive management.


Neck Mass Adenopathy

Neck Mass Adenopathy. A few studies suggested that US can distinguish between metastatic and inflammatory neck nodes [41-47]. Although these results are promising, scans are user dependent. US serves as a powerful tool for image-guided sampling [48], which is beyond the scope of this document. Advantages of US include the ability to be performed at the point of care and to expedite sampling [14]; however, US is limited for comprehensive evaluation of the deep spaces of the neck, and for larger, multispatial, and malignant lesions. US may play a future rule in identifying unknown primary mucosal tumors, notably in the oropharynx [49]. Techniques such as US elastography and contrast-enhanced US are being explored for possible future clinical applications [44,45,50-58]. FDG-PET/CT Skull Base to Mid-Thigh While there is established literature regarding the use of PET using the tracer fluorine-18-2-fluoro-2-deoxy-D- glucose (FDG)/CT for staging and surveillance of head or neck malignancy, FDG-PET/CT is not an initial imaging study for evaluation of a nonpulsatile neck mass. FDG-PET/MRI Skull Base to Mid-Thigh While there is growing literature regarding the use of FDG-PET/MRI for staging and surveillance of head or neck malignancy, FDG-PET/MRI is not an initial imaging study for evaluation of a nonpulsatile neck mass. Arteriography Cervicocerebral There is no evidence to support the use of catheter angiography for evaluation of a nonpulsatile neck mass. Neck Mass/Adenopathy CT Neck Neck CT should be performed with IV contrast. Dual-phase CT imaging (without and with IV contrast) is not usually necessary. CT performed only without IV contrast may be helpful in a small minority of cases. Contrast is useful for distinguishing vessels from lymph nodes and confirming whether a mass is hypervascular as many pulsatile neck masses (especially those in level II or III) are lymph nodes overlying the carotid artery rather than true vascular masses.


Neck Mass Adenopathy

Neck Mass Adenopathy. There is no current literature comparing the efficacy of contrast-enhanced CT to CTA or MRI and MRA for the evaluation of a pulsatile neck mass. Advances in lower dose protocols and reconstruction vary among vendors [32], and all imaging should reflect ALARA practices [33]. CTA Neck Although CTA is optimized to visualize the cervical arteries, the soft tissues are usually well characterized. There is no current literature comparing efficacy of contrast-enhanced CT to CTA or MRI and MRA for the evaluation of a pulsatile neck mass. MRI Neck The primary advantage of MRI is improved soft-tissue intrinsic contrast. A noncontrast MRI also serves a role for anatomic definition of a pulsatile neck mass in patients who cannot receive contrast. There is no current literature comparing efficacy of contrast-enhanced CT to CTA or MRI and MRA for the evaluation of a pulsatile neck mass. Arterial phase, time-resolved (4-D) MRI may be useful for evaluation of possible paragangliomas in the head and neck [59-61], but it is not an initial imaging study of a new palpable neck mass. MRA Neck MRA is complementary to MRI in the evaluation of a pulsatile neck mass to achieve anatomic and vascular detail. Time resolved (4-D) contrast-enhanced MRA technique may be useful for characterization of head and neck arteriovenous malformations [62]. There is no current literature comparing efficacy of contrast-enhanced CT to CTA or MRI and MRA for the evaluation of a pulsatile neck mass. The use of contrast for MRA is institution dependent but generally preferred. US Neck US may identify a distinct mass overlying or adjacent to an artery, may confirm vascularity of a lesion, or may be useful to confirm a clinical suspicion of a tortuous artery. The characteristic US appearance of phleboliths may aid in the diagnosis of low-flow vascular malformations [59].


Neck Mass Adenopathy

Neck Mass Adenopathy. FDG-PET/CT Skull Base to Mid-Thigh Patients with suspected recurrent paraganglioma may benefit from additional types of PET imaging beyond the scope of this document [63-65]; however, PET/CT is not an initial imaging study for evaluation of a pulsatile neck mass. FDG-PET/MRI Skull Base to Mid-Thigh Patients with suspected recurrent paraganglioma may benefit from additional types of PET imaging beyond the scope of this document [63-65]; however, PET/MRI is not an initial imaging study for evaluation of a pulsatile neck mass. Arteriography Cervicocerebral Catheter angiography may be used for surgical planning and endovascular treatment or for further characterization of vascular neck lesions identified on US or cross-sectional imaging; however, it is not an initial imaging study for evaluation of a pulsatile neck mass. Variant 3: Parotid region mass(es). Initial imaging. Imaging generally cannot determine if a newly symptomatic or palpable parotid lesion is benign or malignant. However, imaging may help determine whether the mass is arising from within or outside the parotid gland, the characteristics of the mass, and whether additional masses are present [66]. An extraparotid mass usually reflects a lymph node. For an intraparotid lesion, differential considerations include lymph nodes, benign, malignant, inflammatory, and congenital etiologies. Although certain imaging findings often suggest a specific diagnosis for a parotid mass, histologic diagnosis is usually needed to exclude malignancy [26,67-72]. Clinical history and Neck Mass/Adenopathy physical examination also influences the workup as numbness, trismus, fixation, and facial weakness may suggest a malignant etiology. Radiologist consultation is essential to achieve appropriate anatomic coverage. CT Neck CT face and/or neck with IV contrast is commonly used to evaluate palpable parotid region abnormalities, usually in the setting of suspected parotid acute inflammation [73].


Neck Mass Adenopathy

Neck Mass Adenopathy. CT performed only without IV contrast may be helpful in a small number of cases. Bony details (landmarks, erosion, remodeling) and sialoliths are better delineated by CT compared with MRI [74]. Dual phase (without and with IV contrast) is not usually necessary as most sialoliths are not obscured by contrast. A noncontrast CT study is usually not indicated in patients presenting with a neck mass suspected of being a swollen major salivary gland that is due to obstructing sialolith [20]. CT imaging coverage of the entire neck should be considered if full assessment of regional nodes is required. Advances in lower dose protocols and reconstruction vary among vendors [32], and all imaging should reflect ALARA practices [33]. CT perfusion imaging is still a research tool for evaluation of parotid pathology [75,76]. CT Neck Parotid Sialography In the absence of acute infection, CT sialography may provide detailed assessment of the parotid ducts if there is a clinical concern for duct obstruction. CTA Neck There is no evidence to support the use of CTA for evaluation of a parotid region mass. MRI Neck Parotid Sialography Noninvasive MRI sialography may provide assessment of the parotid ducts [88] complementary to anatomic MRI of the face or neck, if there is a clinical concern for acute parotitis in the setting of duct obstruction. MRA Neck There is no evidence to support the use of MRA for evaluation of a parotid region mass. US Neck US is adept at localization of parotid versus extraparotid masses [77,89], and identifying features suspicious for malignancy [90]. Deep lobe lesions are generally not as well delineated with US as in the superficial lobe. Much of the published literature focuses on US-guided fine-needle aspiration, and not the diagnostic utility of US. Contrast-enhanced US and US elastography are newer techniques currently being explored for evaluation of salivary pathology [71,91-94].


Neck Mass Adenopathy

Neck Mass Adenopathy. FDG-PET/CT Skull Base to Mid-Thigh While there is established literature regarding the use of FDG-PET/CT for staging and surveillance of parotid malignancy, FDG-PET/CT is not an initial imaging study for evaluation. FDG-PET/MRI Skull Base to Mid-Thigh There is no evidence to support the use of FDG-PET/MRI for evaluation of a new parotid mass. Arteriography Cervicocerebral There is no evidence to support the use of catheter angiography for evaluation of a new parotid mass. Fluoroscopy Sialography Parotid In the absence of acute infection, conventional fluoroscopic parotid sialography may provide detailed assessment of the parotid ducts if there is a clinical concern for duct obstruction. Neck Mass/Adenopathy Variant 4: Child. Neck mass(es). Not parotid region or thyroid. Initial imaging. In children who present with neck masses, congenital etiologies should be added to differential diagnostic considerations [6,95] in addition to infectious and malignant etiologies. Clinical examination features and correlation with onset, change in mass size, fluctuance, fever, overlying skin erythema, or recent trauma are important to guiding imaging. CT Neck CT with IV contrast can be performed in children suspected of a having a malignancy or a deep neck infection that may require surgery [21,29,96]. CT has reduced or absent sedation requirements given the shorter examination time. Dual phase (without and with IV contrast) is not usually necessary, as most sialoliths are not obscured by contrast. [20]. CT performed only without IV contrast may be useful in some cases. Advances in lower dose protocols and reconstruction vary among vendors [32], and all imaging should reflect ALARA practices [33]. CTA Neck There is no evidence to support the use of CTA for evaluation of a palpable neck mass in a child. MRI Neck MRI of the neck can be performed in children suspected of having a malignancy or a deep neck abscess that may require surgical drainage [21,29,96].


Neck Mass Adenopathy

Neck Mass Adenopathy. Additionally, in suspected vascular malformation, MRI provides detail of trans-spatial extent and adjacent neurovascular structures [97,98]. The addition of contrast is usually helpful for evaluation of suspected vascular lesions [99]; however, it should be considered on a case-by-case basis as it is not always necessary to achieve diagnosis [100]. MRA Neck There is no evidence to support the use of MRA for evaluation of a palpable neck mass in a child, though time- resolved postcontrast MRA could be useful for evaluating venous malformations and other pathology [59]. Contrast may not be necessary for defining arterial anatomy. US Neck In children suspected of having a congenital abnormality, US is useful in differentiating solid from cystic neck lesions and in discriminating high-flow from low-flow vascular malformations [59,101-103]. Color-flow Doppler US is also helpful for characterizing vascular flow in solid lesions [41,104]. US may suffice for evaluation of superficial infection [105]. FDG-PET/CT Skull Base to Mid-Thigh There is no evidence to support the use of FDG-PET/CT for evaluation of a palpable neck mass in a child. FDG-PET/MRI Skull Base to Mid-Thigh There is no evidence to support the use of FDG-PET/MRI for evaluation of a palpable neck mass in a child. Arteriography Cervicocerebral There is no evidence to support the use of catheter angiography for evaluation of a palpable neck mass in a child. Summary of Recommendations Variant 1: CT neck with IV contrast or MRI neck without and with IV contrast is usually appropriate for the initial imaging of nonpulsatile neck masses, not parotid region or thyroid. These procedures are equivalent alternatives. Variant 2: CT neck with IV contrast, CTA neck with IV contrast, MRI neck without and with IV contrast, or MRA neck is usually appropriate for the initial imaging of pulsatile neck masses, not parotid region or thyroid. These procedures are equivalent alternatives, although CTA or MRA may be complementary to CT and MRI.


Liver Lesion Initial Characterization

Liver Lesion Initial Characterization.  Introduction/Background Incidental liver masses are commonly discovered on imaging performed for other indications. Because the prevalence of benign focal liver lesions in adults is high, with at least one lesion seen in up to 15% of patients, accurate characterization of incidentally detected lesions is an important objective of diagnostic imaging [1]. Benign lesions are very common in the liver, and even in patients with primary malignancy, benign lesions unrelated to the known malignancy can be found in nearly 30% of patients [2]. Common benign liver masses include cysts, hemangiomas, and focal nodular hyperplasia (FNH). Common malignant tumors include metastases and hepatocellular carcinomas (HCCs). Less common liver masses include hepatocellular adenoma, intrahepatic cholangiocarcinoma, fibrolamellar HCC, biliary cystadenoma and cystadenocarcinoma, lymphoma, stromal tumors, and a variety of sarcomas. On occasion, benign lesions and pseudolesions may mimic liver tumors. These mimics include focal fat deposition or sparing, intrahepatic vascular shunts, transient hepatic attenuation/intensity difference, abscess, hematoma, and peliosis hepatis. Patients with cirrhosis are a special patient population in whom certain benign (regenerating nodules), premalignant (dysplastic nodules), malignant (HCC), and nontumorous (confluent hepatic fibrosis) masses as well as pseudolesions (vascular shunts) are more prevalent than in the general population [3]. For each of the variants in this document, it is assumed that an imaging study has identified a lesion that was not fully characterized by the study that detected it. Prior imaging studies may include ultrasonography (US) with color- flow evaluation, noncontrast or contrast-enhanced multidetector helical CT, or noncontrast or contrast-enhanced MRI.


Liver Lesion Initial Characterization

Liver Lesion Initial Characterization. Management recommendations of incidental liver lesions were addressed in a recent white paper by the ACR Incidental Findings Committee (Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee) [4]. The document addressed management guidance for incidental liver lesions detected on CT only. In contrast, this document addresses approaches to characterization of hepatic lesions detected with various modalities and in various clinical scenarios. For purposes of increased clarity in this document, we combined the low-risk and average-risk individual into one category using the definitions as stated in the white paper (any age with no known malignancies, hepatic dysfunction, risk factors for HCC, or symptoms attributable to the liver). The definition of a high-risk individual in this document differs from that in the white paper in that we separate those individuals with pre-existing liver disease (cirrhosis and chronic hepatitis B without cirrhosis) from those with a known primary malignancy. Special Imaging Considerations When considering a definitive diagnosis of liver lesions, the dynamic pattern of lesion enhancement can guide the final diagnosis. Therefore, at least two dynamic imaging phases (ie, dual-phase) are required for characterization of most liver lesions. These phases include hepatic arterial phase and portal venous phase and are applicable to CT, aMontefiore Medical Center, Bronx, New York. bPanel Vice-Chair, Northwestern University, Chicago, Illinois. cPanel Chair, Johns Hopkins University School of Medicine, Baltimore, Maryland. dUniversity of Arizona, Banner University Medical Center, Tucson, Arizona. eDuke University Medical Center, Durham, North Carolina. fUniversity of Texas Health Science Center at Houston and McGovern Medical School, Houston, Texas; American Gastroenterological Association. gInterventional Endoscopy and Pancreatic Diseases, New Haven, Connecticut; American Gastroenterological Association.


Liver Lesion Initial Characterization

Liver Lesion Initial Characterization. hUMass Medical School, Worcester, Massachusetts. iUniversity of Florida College of Medicine, Gainesville, Florida. jRush University Medical Center, Chicago, Illinois; American College of Surgeons. kNew York University Medical Center, New York, New York. lStanford University Medical Center, Stanford, California. mUniversity of Alabama Medical Center, Birmingham, Alabama. nUniversity of Alabama Medical Center, Birmingham, Alabama. oJohns Hopkins Bayview Medical Center, Baltimore, Maryland. pUniversity of Illinois College of Medicine, Chicago, Illinois; American College of Physicians. qJohns Hopkins Hospital, Baltimore, Maryland. rSpecialty Chair, Virginia Commonwealth University Medical Center, Richmond, Virginia. Reprint requests to: publications@acr.org Liver Lesion-Initial Characterization For MRI, extracellular gadolinium-based contrast agents are commonly used in a variety of clinical settings. However, hepatobiliary contrast agents were developed to assist with detection and characterization of liver lesions. Two such agents are available: gadoxetate disodium and gadobenate dimeglumine. Hepatobiliary agents have the advantage of hepatobiliary phase (HBP) in addition to the dynamic postcontrast phases. In the HBP, parenchymal uptake of the contrast agent provides avid enhancement of the liver and therefore the ability to detect nonhepatocellular lesions. Of the two agents, gadoxetate is used more widely for HBP imaging as its HBP occurs approximately 20 minutes after injection as compared with 1 to 2 hours when using gadobenate. A positron-emitting radioisotope-labeled somatostatin analogue called Ga-68-DOTATATE utilized in PET/CT is designed to image neuroendocrine tumors (NETs). It offers a higher spatial resolution and considerably shorter imaging times compared with In-111 somatostatin receptor or metaiodobenzylguanidine scintigraphy [8]. Discussion of Procedures by Variant Variant 1: Indeterminate, greater than 1 cm liver lesion on initial imaging with US.


Liver Lesion Initial Characterization

Liver Lesion Initial Characterization. Normal liver. No suspicion or evidence of extrahepatic malignancy or underlying liver disease. CT Abdomen In some cases, establishing the benign nature of the lesion, rather than a definitive diagnosis is sufficient. In differentiation between malignant and benign lesions, contrast-enhanced CT is accurate in 74% to 95% of cases [9,10]. Definitive diagnosis can be established on contrast-enhanced CT in 71% of patients, with additional imaging recommended in 10% of patients [11]. For patients with incidental liver lesions, multiphase contrast-enhanced CT has 91% to 95% accuracy for diagnosis of hemangioma, 85% to 93% accuracy for the diagnosis of FNH, and 96% to 99% accuracy for diagnosis of HCC [10,12]. For lesions detected on grayscale US, contrast-enhanced CT has sensitivity of 72% to 91%, specificity of 38% to 82%, positive predictive value (PPV) of 92%, negative predictive value (NPV) of 80%, and accuracy of 80% to 88% for establishing a definitive diagnosis [9,13]. CT of the abdomen with and without IV contrast is not recommended for this clinical scenario because there is no added value for unenhanced images. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT in this clinical scenario. DOTATATE PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of Ga-68-DOTATATE PET/CT in this clinical scenario. Octreotide Scan with SPECT or SPECT/CT Chest and Abdomen There is no relevant literature to support the use of In-111 somatostatin receptor scan with single-photon emission computed tomography (SPECT) or SPECT/CT in this clinical scenario. MRI Abdomen In lesions detected on grayscale US, one study of MRI with and without intravenous (IV) contrast has sensitivity of 82% and specificity of 43% for establishing an exact diagnosis [14].


Liver Lesion Initial Characterization

Liver Lesion Initial Characterization. In another series, MRI with and without IV contrast is able to establish a definitive diagnosis in 95% of liver lesions, which is significantly higher than contrast- enhanced CT [11]. Furthermore, only 1.5% of patients with MRIs require recommendation for further imaging as opposed to 10% with CT [11]. Performance characteristics of MRI depend on the sequences and type of contrast, as well as the lesion itself. A combination of diffusion-weighted imaging (DWI) and HBP allows correct classification of lesions as benign or malignant in 91% of cases and exact characterization in 85% of cases [15]. Gadoxetate-enhanced MRI has an accuracy of 95% to 99% for diagnosis of hemangioma, accuracy of 88% to 99% for the diagnosis of FNH, and accuracy of 97% for diagnosis of HCC in patients with incidentally discovered liver lesions [10,12]. For differentiation between adenoma and FNH, low signal on HBP is 100% specific, 92% sensitive, Liver Lesion-Initial Characterization and 97% accurate for hepatocellular adenoma [16]. However, it should be noted that inflammatory adenoma can mimic FNH on MRI [17]. For the diagnosis of a hemangioma, MRI with extracellular gadolinium contrast has sensitivity of 93%, specificity of 99%, accuracy of 98%, PPV of 96%, and NPV of 99% [18]. Although apparent diffusion coefficient (ADC) values of solid benign lesions are higher than those of the solid malignant lesions, there is a considerable overlap of the ADC values between the two groups [19]. Therefore, in patients without a history of malignancy, the value of DWI for differentiating solid liver masses may be limited. There is no relevant literature that has assessed the performance of MRI without IV contrast specifically for this clinical scenario. Therefore, the committee recommendations on the use of MRI without IV contrast are based primarily on expert opinion.


Liver Lesion Initial Characterization

Liver Lesion Initial Characterization. In some cases, MRI without IV contrast may be appropriate, particularly if the initial US has a high index of suspicion for the diagnosis of a cyst. Image-Guided Biopsy Liver An indeterminate liver lesion detected on US is often further evaluated with a diagnostic CT or MRI prior to biopsy, in order to avoid biopsy of solid benign liver lesions such as hemangiomas or areas of FNH [4]. Percutaneous image-guided biopsy may be necessary to establish the diagnosis, particularly when the imaging features on a CT or MRI examination indicate possibility of malignancy. In some liver lesions, such as lymphoma, histopathologic analysis is the only technique that can make a definitive diagnosis [20]. Various techniques exist for guidance of the biopsy, and US and CT are the most commonly utilized modalities for biopsy guidance. When a biopsy is performed to diagnose or rule out malignancy in indeterminate lesions, the overall technical success rate under grayscale US guidance is 74%, which can be increased to 100% under CEUS guidance [21,22]. The percentage of tumor cells in the biopsy sample is greater with a higher number of collected biopsy samples [23]. Furthermore, for lesions not seen on grayscale US, the success rate for CEUS-guided biopsy can be as high as 88% to 96% [24,25]. US fusion with CT or MRI, can be used for percutaneous biopsy of lesions with poor sonographic conspicuity, with a 96% technical success rate [25]. Lesions that are isointense on CT can also present a challenge for CT-guided biopsy; however, use of anatomic landmarks or IV contrast can achieve accuracy of 96% to 98% [26]. Image-guided biopsies carry a risk of postbiopsy bleeding, which may be as high as 9% to 12%, particularly with hypervascular lesions [27,28]. In addition, a very small risk of needle-track seeding exists. RBC Scan Abdomen and Pelvis There is no relevant literature to support the use of a Tc-99m red blood cell (RBC) scan in this clinical scenario.


Liver Lesion Initial Characterization

Liver Lesion Initial Characterization. Liver Spleen Scan There is no relevant literature to support the use of a Tc-99m sulfur colloid scan in this clinical scenario. US Abdomen with Contrast For patients with a lesion on grayscale US, addition of CEUS reduces the number of indeterminate diagnoses from 57% to 6%, and the sensitivity and specificity improve from 49% and 25% at baseline US to 93% and 75% with CEUS, respectively [29]. Furthermore, CEUS can reach a specific diagnosis in 77% to 93% and distinguish benign versus malignant lesions in 89% to 97% of indeterminate liver lesions discovered on grayscale US [9,30-32]. Of the complex cystic lesions found on grayscale US, CEUS correctly categorizes 95% of the malignant cases [33]. CEUS is comparable to CT for establishing a diagnosis for lesions detected on grayscale US, with sensitivity of 94% to 96%, specificity of 75% to 83%, PPV of 92%, NPV of 88%, and accuracy of 88% to 90% [13,14,29]. CEUS can definitively characterize an additional 41% of hemangiomas that are deemed indeterminate on a grayscale US [34]. For specific diagnoses, CEUS correctly characterizes 89% of areas of focal fat, 80% to 90% of hemangiomas, 87% of complex cysts, 78% of hepatic adenomas, 84% to 94% of FNHs, 86% of abscesses, and 60% of hematomas [14,30,35]. Typical pattern of enhancement on CEUS (eg, centripetal fill in during the arterial phase, hyper- enhanced lesion during venous and late phases) has 88% to 90% sensitivity, 99% specificity, 94% to 95% PPV, 97% to 98% NPV, and 97% accuracy for the diagnosis of hemangiomas [18,36]. In noncirrhotic patients, the hypoechoic pattern in portal and sinusoidal phase (rapid wash-out) or the markedly hypoechoic or anechoic pattern in sinusoidal phase (marked late wash-out) showed a sensitivity, specificity, and accuracy of 97%, 100% and 98%, respectively, for the diagnosis of malignancy [37].