Abnormal Liver Function Tests

Abnormal Liver Function Tests. US Shear Wave Elastography Abdomen US shear wave elastography is increasingly used to assess liver stiffness in chronic liver parenchymal disease. Various US elastography techniques have evolved in recent years that use different shear wave generation and propagation. These include transient elastography, acoustic radiation force impulse elastography, supersonic shear wave, and real-time tissue elastography. Controlled attenuation parameter is a novel method for the measurement of hepatic steatosis that uses the same radiofrequency data used for quantification of liver stiffness. Shi at al [18] performed a meta-analysis to look at performance of controlled attenuation parameter in detection of severity of steatosis (>S1, >S2, >S3). The sensitivity and specificity were 78% and 79% for S1, 85% and 79% for S2 and, 83% and 79% for S3 steatosis, respectively. Receiver operating characteristic analysis was 85% for >S1, 88% for >S2, and 87% for >S3. According to the meta- analysis, controlled attenuation parameter has a good sensitivity and specificity for detecting hepatic fat content; however, accuracy is limited. However, CT is not useful as the first modality of choice for the diagnosis of mildly elevated aminotransferases due to mild fatty infiltration for multiple reasons, including failure to detect early steatosis, lack of accuracy, and reliability [20,23,24]. Abnormal Liver Function Tests CT Abdomen and Pelvis Without and With IV Contrast There is no relevant literature to support the use of CT abdomen and pelvis without and with IV contrast in this clinical scenario. MR Elastography Abdomen MR elastography is the most useful modality to estimate liver fibrosis. MR elastography is currently being investigated to diagnose NAFLD without liver fibrosis and therefore is not an initial investigation.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Chen et al [27] showed higher liver stiffness in patients with steatosis and lobular inflammation than in those with steatosis and lower stiffness when compared with those with parenchymal fibrosis in fatty liver. Chemical shift imaging using T1 gradient echo exploits the differences in the resonance frequencies of water and fat proton signals yielding 2-point Dixon T1 in-phase and opposed-phase with fat and iron depiction. However, T2* decay from hepatic iron can erroneously lead to an underestimation of liver fat content by reducing in-phase signal, particularly at longer time to echo [28-31]. Proton density fat fraction is a quantitative and reproducible method for fat estimation that uses chemical shift while eliminating or reducing the effects of confounding factors, such as T2 decay. Proton density fat fraction is an accurate (area under the receiver operating characteristic curve = 98.9%; 95% confidence interval, 96.8%-100%) and reliable tool for hepatic lipid assessment (grade 1 or higher) across different vendors and magnetic field strengths. Recent investigations suggest that quantitative MR methods may serve as a comparable or even better reference standard for fat quantification to reference standard liver biopsy [32,33]. MRI Abdomen Without and With IV Contrast With MRCP There is no relevant literature to support the use of MRI abdomen without and with IV contrast with MR cholangiopancreatography (MRCP) in this clinical scenario. Variant 2: Abnormal liver function tests. Hepatocellular predominance with moderate or severe aminotransferase increase. Initial imaging. Breu et al [34], in a large multicenter study, found ischemic hepatitis to be the most common cause for markedly elevated aminotransferase ALT/AST level (5000 IU/L). Ischemic liver injury is a serious condition because it can progress to liver failure and high mortality [35].


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Acute viral hepatitis (hepatitis A and B, hepatitis C), drug-induced liver injury (acetaminophen), and pancreaticobiliary pathologies leading to biliary obstruction and liver injury are other causes of moderate to marked increase in aminotransferases [34]. CT Abdomen and Pelvis Without IV Contrast Although intra- and extrahepatic biliary ductal dilatation may be identified on CT abdomen and pelvis without IV contrast, contrast confers added benefit for assessment of ischemic liver injury and possible useful hemodynamic information, such as sequela of portal hypertension or hepatic congestion. There are advantages to including the pelvis in the CT abdomen and pelvis examination, including detecting pelvic ascites, pelvic collateral vessels in portal hypertension, and possible sources of obstruction (eg, lymphadenopathy). CT Abdomen and Pelvis With IV Contrast Although the findings of acute hepatitis on CT are not specific for the diagnosis, CT may be useful for evaluating the sequela or complications of hepatitis. CT with IV contrast can also identify ischemic hepatitis. Acute hepatitis on contrast-enhanced CT demonstrates arterial heterogeneity, periportal hypoattenuation, perihepatic lymphadenopathy (>7 mm), and ascites in decreasing order of prevalence [37]. A thickened gallbladder Abnormal Liver Function Tests wall on contrast-enhanced CT (mean 5.2 mm) was an independent predictor of severe hepatitis and prolonged cholestasis [37]. An association of enhanced CT findings with phases of acute hepatitis (prodrome, jaundice, recovery) showed small hepatoduodenal lymphadenopathy, perihepatic fat infiltration, gallbladder wall thickening, contraction, or an undulating inner margin, periportal edema, hepatomegaly, splenomegaly, and pelvic fluid collection in 98.8%, 76.5%, 75.3%, 43.5%, 22.4%, 52.9%, and 56.5% of the patients, respectively [38,39].


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Shock liver, leading to ischemic hepatitis, may be secondary to systemic hypoxic or hypotensive causes leading to hypoperfusion of the liver, which may show hypoenhancement of a portion of the liver or entire liver parenchyma. Selective hepatic hypoperfusion due to hepatic arterial of portal venous occlusion could be reversible because of dual blood supply but may result in liver failure or hepatic infarction [40]. There are advantages to including the pelvis in the CT abdomen and pelvis examination, including detecting pelvic ascites as well as collateral vessels in instances of portal venous hypertension. CT Abdomen and Pelvis Without and With IV Contrast CT of the abdomen and pelvis with and without IV contrast is not typically useful for this clinical scenario because there is no benefit from adding unenhanced images. MR Elastography Abdomen Currently there is no role for MR elastography to diagnose acute hepatic inflammation from various causes. Superimposed acute inflammation in chronic viral hepatitis does not impact correlation of stiffness with stage of fibrosis [41,42]. MRI Abdomen with MRCP Although abdominal US is the preferred modality of choice in severely elevated aminotransferase, MRI with IV contrast can be obtained to assess parenchymal inflammation, perfusion, and vascular patency. Inflamed liver parenchyma shows increased signal intensity on T2-weighted images and decreased signal on T1- weighted images with heterogeneous perfusion, similar to CT. Periportal edema can be appreciated as a hyperintense signal on T2-weighted images. Heterogeneous enhancement of the liver in the arterial phase is seen in acute hepatic inflammation from various causes [43-48]. Perihepatic fluid and gallbladder wall edema can be seen on T2-weighted images in acute hepatitis. Hepatic capsular edema may be present in fulminant hepatitis with resultant heterogeneous enhancement on postgadolinium T1- weighted images.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Hepatic infarction is seen as nonenhancing wedge-shaped hepatic parenchyma. Vascular cause for ischemic hepatitis can be identified on postcontrast imaging, including MR angiogram [38,49]. Several investigations have shown impaired uptake of liver-specific agents in hepatic dysfunction. Gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid is a paramagnetic hepatobiliary MR contrast agent, which (due to its OATP1B1/B3-dependent hepatocyte-specific uptake and paramagnetic properties) is used for evaluation of liver function analysis [50-53]. US Abdomen with IV Contrast CEUS is not a first-line imaging modality to assess the hepatic parenchyma in acute severe hepatitis or ischemia. Investigations to use as adjunct to check vascular patency in transplant livers has been tried [60], but there is a lack of relevant literature to support the use of CEUS in this clinical scenario. Abnormal Liver Function Tests US Duplex Doppler Abdomen Duplex Doppler can be added to routine grayscale US to look for vascular patency in patients with suspected ischemic insult. US Shear Wave Elastography Abdomen There is no relevant literature to support the use of US shear wave elastography in toxic or ischemic liver injury. Choledocholithiasis is the most common cause of extrahepatic biliary obstruction and elevated ALP of liver origin. Additional etiologies of extrahepatic biliary obstruction include malignant obstruction, biliary strictures, and infections (eg, AIDS cholangiopathy, and liver flukes). Isolated elevated ALP of hepatic origin (without other elevated liver function tests) that persists over time suggests a chronic cholestatic process, such as partial bile duct obstruction, primary biliary cholangitis, primary sclerosing cholangitis, or drug-induced cholestasis. Infiltrative liver diseases such as sarcoidosis, amyloidosis, and hepatic metastases, among others, may also lead to intrahepatic cholestasis.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. ALP may also be elevated nonspecifically in addition to other elevated liver biochemical tests in all types of liver diseases, including hepatitis, cirrhosis, sepsis, and heart failure. CT Abdomen and Pelvis With IV Contrast Although abdominal US is typically the first-line imaging modality for identifying biliary obstruction, contrast- enhanced CT of the abdomen and pelvis may help define the site of obstruction, potential etiology, and coexistent complications [63]. CT is considered less sensitive than MRI with MRCP for the evaluation of the bile ducts; however, CT may provide useful information regarding the etiology of cholestasis. There are advantages to including the pelvis in the CT abdomen and pelvis examination, including detecting pelvic ascites, pelvic collateral vessels in portal hypertension, and possible sources of obstruction (eg, lymphadenopathy). CT Abdomen and Pelvis Without and With IV Contrast CT of the abdomen and pelvis with and without IV contrast is not typically performed for this clinical scenario because there is no benefit from adding unenhanced images. CT Abdomen and Pelvis Without IV Contrast Although intra- and extrahepatic biliary ductal dilatation may be identified on CT abdomen and pelvis without IV contrast, contrast confers added benefit for assessment of ischemic liver injury and possible useful hemodynamic information, such as sequela of portal hypertension or hepatic congestion. There are advantages to including the pelvis in the CT abdomen and pelvis examination, including detecting pelvic ascites, pelvic collateral vessels in portal hypertension, and possible sources of obstruction (eg, lymphadenopathy). MR Elastography Abdomen MR elastography is currently the most accurate imaging modality for the diagnosis and staging of hepatic fibrosis; however, it has a limited to no role in the initial imaging of suspected cholestasis. Abnormal Liver Function Tests


Abnormal Liver Function Tests

Abnormal Liver Function Tests. MRI Abdomen Without and With IV Contrast With MRCP Abdominal US is typically the first-line imaging modality; however, in the setting of persistently elevated ALP and a negative abdominal sonogram, MRI abdomen without and with IV contrast with MRCP may be useful. Sustained elevation of ALP is significantly correlated with choledocholithiasis on MRCP and may be helpful for triaging patients to endoscopic retrograde cholangiopancreatography (ERCP); however, patients who have common bile duct stones demonstrated on US should proceed directly to ERCP [64,65]. If extra- or intrahepatic biliary ductal dilatation is identified on abdominal US, contrast-enhanced MRI with MRCP is the most useful imaging modality for evaluating the etiology of biliary obstruction. Contrast-enhanced MRI with MRCP facilitates noninvasive evaluation of both intra- and extrahepatic bile ducts, as well as the liver parenchyma [66]. Further, contrast-enhanced MRI with MRCP enables triaging of patients to subsequent interventions, such as stenting with ERCP, brushings by endoscopic US, and image-guided or laparoscopic biopsy, as well as serving as a guide for the subsequent approach with these interventions. MRI performed with diffusion sequences and hepatobiliary contrast agents can be advantageous in lesion detection and characterization, although a decreased uptake of hepatobiliary agents by hepatocytes might decrease diagnostic accuracy, especially in patients with reduced liver function [51]. MRI Abdomen Without IV Contrast With MRCP Although less sensitive than contrast-enhanced MRI, a noncontrast MRI (including MRCP) may be useful for identifying biliary obstruction as a source of cholestasis. Contrast administration improves the sensitivity for detection of acute cholangitis, hepatic metastases, and the detection of primary sclerosing cholangitis.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Furthermore, excretion of hepatobiliary contrast and opacification of the biliary ducts and gallbladder provide additional information regarding the site and etiology of obstruction, as well as liver function [67-69]. US Abdomen Patients with elevated ALP suspected to be liver in origin and no alternative etiology should undergo transabdominal US to assess for dilated intra- or extrahepatic ducts and gallstones as the possible cause. Gallstone disease is prevalent with approximately 10% of adults having cholelithiasis and approximately 500,000 cholecystectomy operations performed annually [70]. Approximately 18% of adults undergoing cholecystectomy have choledocholithiasis [71,72]. Although abdominal US has a low sensitivity for detection of choledocholithiasis, in part related to frequent overlying bowel gas, it has high specificity [65]. When biliary obstruction is identified on abdominal US, frequently dynamic contrast-enhanced CT, MRI, or CEUS is required for further evaluation of the cause and possibly procedure planning. The absence of gallstones or choledocholithiasis suggests a nongallstone etiology and a normal caliber of the extrahepatic bile duct suggests intrahepatic cholestasis [71-73]. US Abdomen with IV Contrast For initial imaging, there is currently no role for CEUS in the evaluation of cholestasis. CEUS has been assessed for the evaluation of liver fibrosis, which may nonspecifically elevate ALP, and is used in the characterization of potentially obstructing hepatic lesions. Similar to CT and MRI perfusion techniques, CEUS uses contrast media transit characteristics to make deductions about liver hemodynamics that relate to the presence and severity of liver fibrosis and for the characterization of hepatic lesions. US Duplex Doppler Abdomen There is debate regarding the diagnostic value of adding Doppler US to the US abdomen examination for initial imaging.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Doppler US can demonstrate hemodynamic alterations related to infection (such as elevated velocity in the main hepatic artery in acute cholecystitis) or indicative of portal hypertension as seen in fibrosis or infiltrative liver diseases. The diagnostic value of Doppler US of the portal vein for the evaluation of liver function is still controversial [74]. US Shear Wave Elastography Abdomen There is no relevant literature to support the use of US shear wave elastography in the evaluation of cholestasis. US shear wave elastography is used to assess for evaluation of liver fibrosis, which may nonspecifically elevate ALP; however, it has a limited to no role in the initial imaging of suspected cholestasis. US Abdomen US is the most useful imaging modality to evaluate conjugated hyperbilirubinemia due to liver parenchymal cause (alcoholic or viral hepatitis and cirrhosis) or biliary obstruction. US shows a positive predictive value of 98% and a sensitivity in the range of 65% to 95% for the diagnosis of liver parenchymal disease. Biliary obstruction can be demonstrated on US with a wide range of sensitivity (32%-100%) and specificity (71%-97%); however, the cause for distal obstruction may be obscured by overlying bowel gas [54]. US Abdomen with IV Contrast There is no relevant literature to support the use of CEUS in this clinical scenario. caxuda US Duplex Doppler Abdomen US duplex Doppler abdomen is not useful for this clinical scenario. US Shear Wave Elastography Abdomen US shear wave elastography is not useful as the first-line imaging modality to assess hyperbilirubinemia. Liver fibrosis can be demonstrated using elastography techniques with improved accuracy in higher stages of fibrosis (area under the curve, 0.88 and 0.91 for S2 and S4 fibrosis, respectively) [18]. There is no evidence to support use of US shear wave elastography in biliary obstruction.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. CT Abdomen and Pelvis With IV Contrast CT abdomen with IV contrast can be used to look for morphologic changes of chronic liver parenchymal disease and its complications. CT can help identify the site of obstruction and the potential etiologies. MRI with MRCP is superior to evaluate the biliary system. Malignant biliary strictures can be identified with a high sensitivity (95%), specificity (93.35%), and accuracy (88.5%) on CT [79]. Abnormal Liver Function Tests CT abdomen with IV contrast is very accurate for diagnosis and staging of pancreaticobiliary malignancies, which can present with hyperbilirubinemia. Tumor resectability and surgical planning for both pancreatic and biliary cancers can be done using CT. There are advantages to including the pelvis in the CT abdomen and pelvis examination, including detecting lymphadenopathy and pelvic ascites. CT Abdomen and Pelvis Without and With IV Contrast CT of the abdomen and pelvis with and without IV contrast is not typically useful for this clinical scenario because there is no benefit from adding unenhanced images. CT Abdomen and Pelvis Without IV Contrast Unenhanced CT has limited utility in assessing biliary obstruction (including etiologies) and liver fibrosis. MRI Abdomen with MRCP As discussed in Variant 3 above, MRI with MRCP is the most useful for evaluating the etiology of biliary obstruction. Contrast is helpful to look for cholangitis and assess malignant etiologies of biliary obstruction. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www. acr.org/ac. Abnormal Liver Function Tests 12 2.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Neuschwander-Tetri BA, Unalp A, Creer MH, Nonalcoholic Steatohepatitis Clinical Research N. Influence of local reference populations on upper limits of normal for serum alanine aminotransferase levels. Arch Intern Med 2008;168:663-6. 3. Pettersson J, Hindorf U, Persson P, et al. Muscular exercise can cause highly pathological liver function tests in healthy men. Br J Clin Pharmacol 2008;65:253-9. 4. Arshad T, Golabi P, Henry L, Younossi ZM. Epidemiology of Non-alcoholic Fatty Liver Disease in North America. Curr Pharm Des 2020;26:993-97. 5. Cotter TG, Rinella M. Nonalcoholic Fatty Liver Disease 2020: The State of the Disease. Gastroenterology 2020;158:1851-64. 6. Chen CL, Cheng YF, Yu CY, et al. Living donor liver transplantation: the Asian perspective. Transplantation 2014;97 Suppl 8:S3. 7. Singh D, Das CJ, Baruah MP. Imaging of non alcoholic fatty liver disease: A road less travelled. Indian J Endocrinol Metab 2013;17:990-5. 8. Hernaez R, Lazo M, Bonekamp S, et al. Diagnostic accuracy and reliability of ultrasonography for the detection of fatty liver: a meta-analysis. Hepatology 2011;54:1082-90. 9. Saadeh S, Younossi ZM, Remer EM, et al. The utility of radiological imaging in nonalcoholic fatty liver disease. Gastroenterology 2002;123:745-50. 10. Lee SS, Park SH, Kim HJ, et al. Non-invasive assessment of hepatic steatosis: prospective comparison of the accuracy of imaging examinations. J Hepatol 2010;52:579-85. 11. van Werven JR, Marsman HA, Nederveen AJ, et al. Assessment of hepatic steatosis in patients undergoing liver resection: comparison of US, CT, T1-weighted dual-echo MR imaging, and point-resolved 1H MR spectroscopy. Radiology 2010;256:159-68. 12. Walas MK, Skoczylas K, Gierblinski I. Standards of the Polish Ultrasound Society - update. The liver, gallbladder and bile ducts examinations. J Ultrason 2012;12:428-45. 13. Mancini M, Prinster A, Annuzzi G, et al.


Abnormal Liver Function Tests

Abnormal Liver Function Tests. Sonographic hepatic-renal ratio as indicator of hepatic steatosis: comparison with (1)H magnetic resonance spectroscopy. Metabolism 2009;58:1724-30. 14. Webb M, Yeshua H, Zelber-Sagi S, et al. Diagnostic value of a computerized hepatorenal index for sonographic quantification of liver steatosis. AJR Am J Roentgenol 2009;192:909-14. 15. Cocciolillo S, Parruti G, Marzio L. CEUS and Fibroscan in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis. World J Hepatol 2014;6:496-503. 16. Dietrich CF, Lee JH, Gottschalk R, et al. Hepatic and portal vein flow pattern in correlation with intrahepatic fat deposition and liver histology in patients with chronic hepatitis C. AJR Am J Roentgenol 1998;171:437-43. 17. Tarzamni MK, Khoshbaten M, Sadrarhami S, et al. Hepatic Artery and Portal Vein Doppler Indexes in Non- alcoholic Fatty Liver Disease Before and After Treatment to Prevent Unnecessary Health Care Costs. Int J Prev Med 2014;5:472-7. 18. Shi KQ, Tang JZ, Zhu XL, et al. Controlled attenuation parameter for the detection of steatosis severity in chronic liver disease: a meta-analysis of diagnostic accuracy. J Gastroenterol Hepatol 2014;29:1149-58. 19. Lawrence DA, Oliva IB, Israel GM. Detection of hepatic steatosis on contrast-enhanced CT images: diagnostic accuracy of identification of areas of presumed focal fatty sparing. AJR Am J Roentgenol 2012;199:44-7. 20. Park SH, Kim PN, Kim KW, et al. Macrovesicular hepatic steatosis in living liver donors: use of CT for quantitative and qualitative assessment. Radiology 2006;239:105-12. 21. Kodama Y, Ng CS, Wu TT, et al. Comparison of CT methods for determining the fat content of the liver. AJR Am J Roentgenol 2007;188:1307-12. 22. Ricci C, Longo R, Gioulis E, et al. Noninvasive in vivo quantitative assessment of fat content in human liver. J Hepatol 1997;27:108-13. 23. Birnbaum BA, Hindman N, Lee J, Babb JS.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty.  Introduction/Background Total knee arthroplasty (TKA), primarily used to treat pain and improve function in patients with symptomatic advanced knee osteoarthritis, is the most commonly performed joint replacement procedure in the United States [1,2]. In 2012, >670,000 knee replacement procedures were performed in the United States [3], which represents an increase of 86% since 2003 [4]. It is estimated that 4 million patients in the United States are currently living with a knee replacement [5]. By 2030, it is estimated that the annual demand for primary TKA will grow by 673% to 3.48 million [6]. Factors contributing to the rising number of TKAs include population growth; aging and increased longevity of the population; expanded indications for performing TKA, especially in individuals >65 years of age; obesity; decline in postprocedure complications; and increased patient demand [7]. Special Imaging Considerations In some patients with knee arthroplasties, repeated hemarthroses are caused by synovial hyperemia or true arteriovenous malformations. These patients can be successfully diagnosed with angiography and treated with embolization. In rare instances, geniculate and popliteal vessel injuries may occur during surgery [15]. A recent study reports single-photon emission CT (SPECT)/CT arthrography with Tc-99m sulfur colloid has a high diagnostic accuracy (97%) in the evaluation of loosening of both hip and knee arthroplasties in patients with persistent postprocedural pain [16]. Barnsley et al [17] also found arthrography with SPECT/CT to be an accurate means of identifying aseptic prosthetic joint loosening. aPenn State Milton S. Hershey Medical Center, Hershey, Pennsylvania and Uniformed Services University of the Health Sciences, Bethesda, Maryland. bPanel Chair, Mayo Clinic Arizona, Phoenix, Arizona. cUniversity of Wisconsin School of Medicine and Public Health, Madison, Wisconsin. dPenn State Health Milton S. Hershey Medical Center, Hershey, Pennsylvania.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. eMayo Clinic, Rochester, Minnesota. fEmory University, Atlanta, Georgia; Committee on Emergency Radiology-GSER. gHospital for Special Surgery, New York, New York. hPenn State Health, Hershey, Pennsylvania, Primary care physician. iDuke University Medical Center, Durham, North Carolina. jUniversity of Missouri Health Care, Columbia, Missouri. kSpecialty Chair, University of Kentucky, Lexington, Kentucky. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org Imaging After Total Knee Arthroplasty OR Discussion of Procedures by Variant Variant 1: Follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging. 3-Phase Bone Scan Knee There is insufficient evidence to support the use of 3-phase bone scan for the initial evaluation of TKA. CT Arthrography Knee There is insufficient evidence to support the use of CT arthrography for the initial evaluation of TKA. CT Knee With IV Contrast There is insufficient evidence to support the use of CT with intravenous (IV) contrast for the initial evaluation of TKA. CT Knee Without and With IV Contrast There is insufficient evidence to support the use of CT without and with IV contrast for the initial evaluation of TKA. CT Knee Without IV Contrast There is insufficient evidence to support the use of CT without IV contrast for the initial evaluation of TKA. FDG-PET/CT Whole Body There is insufficient evidence to support the use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT for the initial evaluation of TKA. Fluoride PET/CT Whole Body There is insufficient evidence to support the use of fluoride PET/CT for the initial evaluation of TKA.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Fluoroscopy Knee There is insufficient evidence to support the use of fluoroscopy for the initial evaluation of TKA. Image-Guided Aspiration Knee There is insufficient evidence to support the use of image-guided aspiration for the initial evaluation of TKA. MRI Knee Without and With IV Contrast There is insufficient evidence to support the use of MRI without and with IV contrast for the initial evaluation of TKA. MRI Knee Without IV Contrast There is insufficient evidence to support the use of MRI without IV contrast for the initial evaluation of TKA. Radiography Knee Radiographs can demonstrate abnormal bone and hardware alignment, periprosthetic lucencies and osteolysis [18- 24], reactive bone formation and periostitis, periprosthetic fractures, evidence of polyethylene liner wear, and cement and heterotopic bone about the knee. Radiographs can often delineate effusion, soft-tissue swelling, foreign bodies, soft tissue emphysema, heterotopic bone, and cement or metal in the soft tissues. Radiographs are useful as the initial evaluation for symptomatology or follow-up. Radiographs are often limited in terms of sensitivity, and further imaging may be required. Imaging After Total Knee Arthroplasty Routine immediate postoperative radiographs are considered unnecessary unless the surgery is complicated or there are specific clinical indications warranting imaging evaluation [25,26], because several studies have indicated that the rate of complications identified in the immediate postoperative setting is low. Ververeli et al [27] compared recovery room radiographs with additional predischarge radiographs and found no change in the postoperative management of 124 consecutive patients with TKAs and suggested eliminating the predischarge radiographs.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Novack et al [25] retrospectively reviewed 4,830 consecutive patients following cemented or uncemented TKAs and concluded routine recovery room radiographs after an uncomplicated primary TKA are not a reliable mechanism for preventing mechanical complications and did not alter patient care. Radiographic evaluation of wear is based on weightbearing AP and lateral radiographs and on axial radiographs. Liner wear is seen as joint space narrowing, varus or valgus deformity, or patellar tilt. An effusion may be present. Findings can be subtle and annual weightbearing radiographs are suggested for detecting subclinical wear [21]. Collier et al [36] found that 87% of measurements performed on standing frontal knee radiographs (on the basis of the minimum distance from the metallic femoral condyle to a line through the top surface of the baseplate at its widest dimension) were within 1 mm of the known implant thickness, but the accuracy decreased for evaluating polyethylene thickness in patients with wear requiring revision. Instability is evaluated on radiographs obtained in extension-flexion position, under varus-valgus stress, and during anterior and posterior drawer maneuvers. In contrast, malalignment refers to suboptimal alignment of the prosthesis components relative to each other (although it is occasionally used to describe alignment of the bones in relation to each other and to the joint) [37] and is evaluated on full-length standing radiographs of the lower extremity [21]. Radiographs including the entire prosthesis are the initial examination for assessment of suspected periprosthetic fractures. Radiographs are also usually satisfactory for assessment of patellar complications [20] and helpful in guiding treatment [38]. Axial radiographs demonstrate the degree of patellar tilt or subluxation [21]. Baldini et al [39] proposed a weightbearing axial radiograph to better assess patellofemoral kinematics.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Although axial radiographs may be used to determine axial rotation of the femoral component [40], CT is most commonly used for this purpose. Leon-Munoz et al [41] have noted CT-scan-based 3-D models and, therefore, supine CT scan, underestimate the degree of deformity at the knee joint, both in varus and valgus; therefore Imaging After Total Knee Arthroplasty preoperative full-leg standing radiographs should be performed for patient-specific instrumentation assisted TKAs, as a complementary study, to analyze the position of the load-bearing axis. Radiographs cannot directly image post-TKA periprosthetic soft-tissue abnormalities. However, radiographic signs of extensor mechanism tendon tears include patella alta, patella baja, localized soft-tissue swelling, posterior subluxation of the tibia, bony avulsions, and dystrophic calcifications within the tendon [21,42]. US Knee There is insufficient evidence to support the use of ultrasound for the initial evaluation of TKA. WBC Scan and Sulfur Colloid Scan Knee There is insufficient evidence to support the use of white blood cell (WBC) scan and sulfur colloid scan for the initial evaluation of TKA. Variant 2: Suspected infection after total knee arthroplasty. Additional imaging following radiographs. Infection is a serious complication of joint arthroplasty and is reported in 0.8% to 1.9% of TKAs [43]. The frequency of infection is increasing as the number of primary arthroplasties increases [44]. Infection may be acute or delayed, with delayed infection defined as occurring at least 3 months postoperatively [45]. In a series, infection was responsible for 37.6% of early revisions and 21.9% of revisions performed >2 years after the initial operation [12]. Staphylococcus aureus and coagulase-negative Staphylococcus species, including Staphylococcus epidermidis, are the most common organisms associated with these infections [46]. Both clinical findings and laboratory tests may serve useful in addition to imaging studies.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Low-grade or chronic TKA infections may be difficult to diagnose preoperatively. Duff et al [18] noted that diagnosis of infection was not obvious in 53% of knees before revision arthroplasty. Pain is the most common presenting symptom of infection, but pain is a nonspecific finding [47]. In acute infection, findings such as pain, swelling, warmth, erythema, and fever are common, whereas chronic infections may be manifested by pain alone [44]. Night pain or pain at rest is characteristic of infection, whereas pain on weightbearing is more characteristic of mechanical loosening. Some authors suggest that infection needs to be excluded in all patients with pain persisting >6 months after joint replacement [18]. Imaging After Total Knee Arthroplasty CT Arthrography Knee CT joint arthrography can assess for lucency with contrast accumulation at the bone/cement/hardware interface. These areas of lucency are not specific for infection versus mechanical loosening. CT Knee With IV Contrast CT has a limited role in the workup of periprosthetic infection. CT with IV contrast could help demonstrate periprosthetic fluid collections and fistulae. Advances in metal artifact reduction may expand the potential role of CT. CT Knee Without and With IV Contrast CT has a limited role in the workup of periprosthetic infection. Noncontrast CT can demonstrate the size and extent of osteolysis, periprosthetic lucencies, intraosseous or soft-tissue gas, and reactive bone formation that might not be evident on radiographs [20,67]. CT with IV contrast could help demonstrate periprosthetic fluid collections and fistulae. Advances in metal artifact reduction may expand the potential role of CT. CT Knee Without IV Contrast CT has a limited role in the workup of periprosthetic infection. Noncontrast CT can demonstrate the size and extent of osteolysis, periprosthetic lucencies, intraosseous or soft-tissue gas, and reactive bone formation that might not be evident on radiographs [20,67].


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Advances in metal artifact reduction may expand the potential role of CT. FDG-PET/CT Whole Body FDG-PET/CT scans may be useful for detecting infection after joint replacement. FDG-PET images reflect relative levels of glucose uptake and thus reflect the localized level of increased metabolic activity. Zhuang et al [68] reported that elevated glycolytic activity causes inflammatory cells such as neutrophils and activated macrophages to be FDG avid at sites of inflammation and infection. Some periprosthetic uptake may occur because of marrow activity, and adding marrow scanning can increase specificity [69]. In these instances, the marrow study would be performed the next day using a different camera type because the marrow scan relies on lower energy photons (PET, 511keV; Tc-99m, 140 keV). Zhuang et al [68] studied 36 painful knee prostheses using FDG-PET and identified 10 of 11 infected cases but had false-positive results in 7 cases (sensitivity of 90.9%, specificity of 72%, and accuracy of 77.8% for detecting infection). This was a lower accuracy than found in assessment of hip prostheses. The cause for the large number of false-positives was not known. Aksoy et al [70] found a positive predictive value (PPV) of 28% (15 of 54) for infection in 54 patients with painful joint prosthesis (24 knee, 48 hip) using FDG-PET. Manthey et al [71] reported that, by analyzing intensity and periprosthetic uptake patterns on FDG-PET, accurate differentiation among aseptic loosening, synovitis, and infection is possible. Kwee and Kwee [72] reports FDG Imaging After Total Knee Arthroplasty uptake at the bone-prosthesis interface has been consistently reported as diagnostic criterion for knee prosthetic joint infection. Kwee et al [73] in a meta-analysis reported that the specificity of FDG-PET for diagnosing infection was significantly lower for knee prostheses (74.8%) than for hip prostheses (89.8%).


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Delank et al [74], in a series of both hip and knee prostheses, found that a negative PET scan excluded infection (100% sensitivity). If the scan was positive, differentiation between wear and infection was not possible. Prandini et al [75] performed a meta- analysis of the diagnostic performance of different radiotracers in peripheral osteomyelitis and prosthetic joint infections, yielding results for FDG-PET with a sensitivity of 94%, a specificity of 87%, a PPV of 87%, an NPV of 94%, and an overall accuracy of 92%. Although metal artifacts have very little impact on nuclear medicine examinations (except as photopenic defects) and create negligible scatter [68,76,77], high PET attenuation coefficients in the area of metal can lead to an overestimation of the PET activity in that region and thereby to a false-positive PET finding. Nonattenuated PET images, which do not manifest this error, can be used in these cases to aid the interpretation of these metal-induced artifacts. Synovitis and aseptic loosening (in hip prostheses) may cause increased FDG uptake [69]. Sterner et al [78] examined 14 patients with painful TKA to detect early aseptic loosening. Overall accuracy was 71% (sensitivity, 100%; specificity, 56%). In addition, Stumpe et al [79] found diffuse synovial and focal extrasynovial FDG uptake in patients with component malrotation. They concluded that this test is noncontributory in individual patients with persistent pain. Studies in patients with hip prostheses have shown that postoperative remodeling can result in artifactual periprosthetic FDG uptake for up to 6 months after implant insertion [80]. Noting the lack of specificity for detection of periprosthetic infection on conventional FDG-PET, Aksoy et al [70] explored the use of FDG- labeled leukocyte PET/CT for imaging patients with painful joint prostheses and found a sensitivity of 93%, a specificity of 97%, a PPV of 93%, and an NPV of 97%. However, this examination is not in general use.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Basu et al [81] found the sensitivity, specificity, PPV, and NPV of FDG-PET in knee prostheses were 94.7%, 88.2%, 69.2%, and 98.4%, respectively, in 87 patients with knee prostheses suspected of being either infected or experiencing noninfectious loosening. Van Acker et al [82] investigated the use of FDG-PET in combination with bone scans and showed no advantage over HMPAO-labeled WBC and bone scans. Comparison of FDG-PET with In-111- labeled leukocyte/Tc-99m-labeled sulfur colloid marrow imaging showed that FDG-PET was less accurate than the leukocyte/marrow scans and could not replace that combination of tests [69]. Fluoride PET/CT Whole Body There is insufficient evidence to support the use of fluoride PET/CT for the initial evaluation of TKA. Imaging After Total Knee Arthroplasty as a month may be necessary for cultures of aspirated fluid to become positive [30]. Weekly repeat aspirations may be needed if the first aspiration is negative and clinical suspicion for infection remains high. Even with a negative preoperative aspiration, intraoperative tissue may indicate infection. Bernard [50], after literature review and a multicenter trial, advocated CRP and joint aspiration as the best tools for diagnosing prosthetic joint infection. When the CRP level is >10 mg/L, repeat joint aspiration or biopsy is suggested. Della Valle [90] also found the combination of ESR and CRP to be a good screening tool for infection, with only one infected knee having negative results on both tests. These authors suggest preoperative aspiration if the ESR or CRP is elevated or if clinical suspicion is high, combined with intraoperative frozen section analysis of the periprosthetic synovial tissue [90].


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. The AAOS gives a moderate strength of recommendation for synovial fluid testing including leukocyte count and neutrophil percentage, aerobic and anaerobic bacterial cultures, leukocyte esterase, alpha-defensin, CRP, and nucleic acid amplification testing (eg, polymerase chain reaction) for bacteria [54]. A recent manuscript advises intraoperative synovial fluid re-cultures are necessary even if the preoperative aspiration culture is positive and any discordance between preoperative aspiration culture and intraoperative synovial fluid culture should be noted [91]. If the joint aspirate culture is positive on the basis of both cell count with differential and positive cultures, then infection is considered likely and treatment is initiated [54,92]. In that setting, no further imaging is supported for the diagnostic workup of the infection. Berbari [46] studied 897 cases of periprosthetic joint infection and found that approximately 7% were associated with negative cultures. If the preoperative synovial cultures remain negative, multiple intraoperative periprosthetic tissues should be submitted for aerobic and anaerobic bacterial culture [54]. MRI Knee Without and With IV Contrast MRI may have a role in the workup of periprosthetic infection. Advances in metal artifact reduction may expand the potential role of MRI. Using metal reduction techniques, Potter and Foo found that infected synovium has hyperintense laminar appearance, distinct from the appearance of particle disease [22,93]. They noted that, in selected cases, MRI may be helpful in detecting extracapsular spread of infection and abscess formation. IV contrast may provide additional benefit in this regard [93]. On the basis of their findings, Plodkowski [94] examined 28 patients with proven infected TKAs and 28 controls with noninfected TKA.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. They found a sensitivity of 86% to 92% and a specificity of 85% to 87%, with almost perfect interobserver agreement, when using the appearance of lamellated hyperintense synovitis to classify infected versus noninfected TKA. Li [95] also reported a different lamellated and hyperintense appearance of the synovium in infected joints, which can be differentiated from frond- like and hypertrophied synovium associated with particle-induced synovitis and from homogeneous fluid-signal intensity effusion associated with a nonspecific synovitis. MRI with metal artifact reduction technique has also been shown to detect osteolysis that is not visible on radiographs [96,97]. Contrast may provide additional benefit in detecting extracapsular spread of infection and abscess formation when compared to noncontrast MRI. MRI Knee Without IV Contrast MRI may have a role in the workup of periprosthetic infection. Advances in metal artifact reduction may expand the potential role of MRI. Using metal reduction techniques, Potter and Foo found that infected synovium has hyperintense laminar appearance, distinct from the appearance of particle disease [22,93]. They noted that, in selected cases, MRI may be helpful in detecting extracapsular spread of infection and abscess formation. Plodkowski et al [94] examined 28 patients with proven infected TKAs and 28 controls with noninfected TKA. They found a sensitivity of 86% to 92% and a specificity of 85% to 87%, with almost perfect interobserver agreement, when using the appearance of lamellated hyperintense synovitis to classify infected versus noninfected TKA. Li et al [95] also reported a different lamellated and hyperintense appearance of the synovium in infected joints, which can be differentiated from frond-like and hypertrophied synovium associated with particle-induced synovitis and from homogeneous fluid-signal intensity effusion associated with a nonspecific synovitis.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. MRI with metal artifact reduction technique has also been shown to detect osteolysis that is not visible on radiographs [96,97]. US Knee US has a limited role in the workup of periprosthetic infection, but it can be readily used to assess soft tissues, including the presence of edema, hyperemia, and fluid collections about the knee joint in patients with TKA. This may be beneficial in certain situations (eg, practices that may perform fluoroscopy-guided aspiration). Imaging After Total Knee Arthroplasty injection of the radiolabeled WBCs [63]. Comparison of activity on the WBC image with activity on a bone scan (usually a 3-phase bone scan) has been advocated. A positive study for infection generally requires focal increased activity on the WBC study in the same location and distribution as the positive 3-phase bone scan [100]. Using a sequential combination of bone and In-111-labeled leukocyte scans in patients with loose or painful knee prostheses found a sensitivity of 88%, a specificity of 78%, a PPV of 75%, and an NPV of 90% for diagnosis of infection. They noted an area of potential utility for leukocyte scans, specifically that a negative indium leukocyte scan might support the absence of infection in otherwise equivocal cases and in situations in which a musculoskeletal pathologist is not available to interpret an intraoperative frozen section [100]. A small sample of indium scans in uncomplicated postoperative TKA patients has shown that inflammation can persist around the operative site in the absence of infection [100]. Bernard et al [50] reported a multicenter trial of various methods for diagnosing hip and knee infections. Scans using tagged WBCs or radiolabeled immunoglobulin demonstrated a sensitivity of 74% and a specificity of 76% for diagnosing infection. A literature review indicates sensitivities of 40% to 96% and specificities of 76% to 100% for WBC scans of joint prostheses [49,50,99-104].


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Therefore, these studies are not useful as routine for differentiating mechanical failure from occult infection in painful loose total knee prostheses. Filippi and Schillaci [105] applied SPECT/CT using a hybrid camera to conventional planar Tc-99m-HMPAO- labeled leukocyte scintigraphy in patients with suspected infection. SPECT/CT was able to differentiate soft-tissue involvement from bone involvement. The authors argued that SPECT/CT might eliminate the necessity for a correlative bone scan with labeled leukocyte scans. WBC scans also have a decreased sensitivity with low-grade infection [66] and a limited neutrophilic component. Labeled leukocyte imaging may lead to a high false-positive rate because leukocytes accumulate in reactive bone marrow as well as in infection and it is not always possible to differentiate between the two [64,106]. The addition of Tc-99m-labeled sulfur colloid bone marrow scanning has been investigated to reduce this confusion. Palestro et al [107] reported that sequential combined leukocyte/marrow imaging was 95% accurate for diagnosing prosthetic knee infection and was superior to bone scans alone or to bone scans in combination with labeled leukocyte imaging. Joseph et al [106] found that low sensitivity and the potential for false-negative results made this combination of scans of limited utility for diagnosing prosthetic infection, and therefore it is no longer used at their institution. In that group of 22 total knee prostheses evaluated and later operated upon, there was a sensitivity of 66%, a specificity of 100%, a PPV of 100%, an NPV of 88%, and an accuracy of 91%. Blanc et al [108] did a retrospective review of 168 patients. They determined Tc-99m-HMPAO labeled leucocyte scintigraphy was more sensitive for knee (84%) than hip prosthesis (57%) but was less specific for knee (52% versus 75%).


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. The addition of blood-pool and flow scans was investigated to determine if hyperemia led to a match of bone marrow-labeled leukocyte uptake (and therefore a false-negative scan). These additional scans decreased the number of false- negative findings (sensitivity, 83%; specificity, 94%; PPV, 83%; NPV, 94%). Overall, the performance of the labeled leukocyte marrow scan protocol was nonetheless thought to be of limited clinical utility [106]. In contrast, Love et al [69] found the combination of In-111-labeled leukocyte/Tc-99m-labeled sulfur colloid marrow scanning to be the reference standard for diagnosing periprosthetic infection. The authors found the combination of labeled WBC and marrow scanning to be 100% sensitive and 100% specific for diagnosing infection in TKA [69]. Semiquantitative assessment of WBC scans using a combination of early and delayed imaging as a substitute for bone marrow imaging produced a >90% sensitivity and specificity in one series [99]. Love et al [109] examined 150 failed joint prostheses with histopathologic correlation and found that leukocyte/marrow imaging yielded a sensitivity of 96%, a specificity of 87%, and an accuracy of 91%. They found that leukocyte/marrow imaging was significantly more accurate than bone scan (50%), bone/gallium scan (66%), and leukocyte/bone imaging (70%) in their population. WBC scan and sulfur colloid scan may have a role in the workup of suspected infection in knee arthroplasty. Variant 3: Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs. Imaging of rotational instability of a TKA is discussed in greater detail under Variant 5. If a patient has undergone a full workup and infection has been excluded, then loosening should be considered as the potential cause of knee pain and periprosthetic lucency. In multiple studies, aseptic loosening has been found to be a common cause of TKA failure [13,110-112].


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Sharkey et al [13] found aseptic loosening to be the major cause of late stage (>2 years) TKA failure. Aseptic loosening may occur either because of inadequate primary fixation or because of failure after successful fixation. It is thought to result from mechanical stresses, osteolysis secondary to particle debris, or poor bone stock [21]. Loosening may be closely related to other forms of mechanical failure such as osteolysis, Imaging After Total Knee Arthroplasty instability, polyethylene liner wear, and periprosthetic fracture. Osteolysis is a leading cause of late TKA revision. Osteolysis, also known as particle disease and aggressive granulomatosis, occurs secondary to macrophage phagocytosis of particle debris. Debris originating from polyethylene, cement, and metal can all be causes of cell- mediated inflammatory response and osteolysis [113], but typically polyethylene is the most common cause. Areas of osteolysis contain granulation tissue with phagocytosed particulate debris [21]. The incidence of osteolysis is higher for cementless, compared with cemented TKA [114]. Osteolysis can occur anywhere but is more common in the region of the femoral condyles near the attachment of the collateral ligaments, along the periphery of the component, and along the access channels to the cancellous bone of the tibia, including screw holes [114,115]. Patients with osteolysis may be asymptomatic early on but can go on to develop pain, swelling, and acute synovitis. Although small areas of osteolysis may be monitored, the presence of large areas of osteolysis suggest component loosening and may require revision surgery [116]. Imaging can also help evaluate available bone stock in preparation for revision surgery. Instability refers to abnormal and excessive displacement of the articular surfaces of the prosthesis [21].


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Instability usually occurs because of surgical error and/or poor prosthesis selection and often results in revision surgery an average of 4 years after the primary arthroplasty [21]. Severe instability can result in dislocation. In a 2014 review of 781 cases of prosthesis failure, Sharkey et al [12] found that instability represented the third most common cause of prosthesis failure overall, accounting for 7.5% of all cases. The concepts of instability, malalignment, and loosening in TKA are closely interrelated [117]. When malalignment of the joint is created at the time of surgery, minor degrees of instability can become a significant problem. By the same token, instability, ongoing over time, can give rise to malalignment, which, in turn, can lead to loosening. Although ligamentous balance/imbalance plays a role in joint instability, it is not the only factor accounting for stability [118]. 3-Phase Bone Scan Knee There is insufficient evidence to support routine use of Tc-99m 3-phase bone scans for the assessment of instability. CT Arthrography Knee CT joint arthrography can assess for lucency with contrast accumulation at the bone/cement/hardware interface. These areas of lucency are not specific for infection versus mechanical loosening. Imaging After Total Knee Arthroplasty CT Knee With IV Contrast CT with IV contrast is not useful for the assessment of aseptic loosening, osteolysis, or instability. CT Knee Without and With IV Contrast CT without and with IV contrast is not useful for the assessment of aseptic loosening, osteolysis, or instability. CT Knee Without IV Contrast Particularly when metal artifact reduction techniques are used, CT can be used to show the extent and width of lucent zones that may be less apparent on radiographs [20]. MRI and CT have both been shown to be more sensitive for detection of osteolysis than radiographs [116].


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. CT can be used to detect osteolysis and to determine the total volume of osteolytic lesions, particularly when metal reduction techniques are used [124]. CT is supported by Math et al [20] to look for osteolysis in patients with painful knee prostheses who have normal or equivocal radiographs and increased uptake on all 3 phases of a bone scan. Reish et al [67] found that only 17% of 48 lesions visible by CT were detected on radiographs. They suggested multidetector CT in cases in which osteolysis is expected, such as when there is aseptic loosening and gross polyethylene wear. CT allows the assessment of rotational positioning of the prosthesis components, which can affect patellofemoral tracking and varus/valgus ligamentous stability in flexion [125]. Imaging of rotational instability of a TKA is discussed in greater detail under Variant 5. There are varying reports on FDG sensitivity, specificity, and accuracy, which are likely in part related to nonuniform interpretation criteria and PET techniques. One overall estimate of FDG sensitivity, specificity, and accuracy in TKA is 96%, 77%, and 83%, respectively [126]. Although FDG is reportedly limited in evaluating patients with chronic knee pain after TKA [66,127], further advancements in FDG-PET may potentially be a promising tool in identifying prosthetic osteolysis [126]. Its exact role in the failed joint prosthesis; however, has yet to be determined. There is insufficient evidence to support routine use of FDG-PET/CT for assessment of instability. Fluoride PET/CT Whole Body Koob et al [128] noted a sensitivity of 95.00%, a specificity of 87.04% and an accuracy of 89.19% for the diagnosis of periprosthetic loosening of total hip and knee prosthesis with fluoride PET/CT. There is insufficient evidence to support routine use of fluoride PET/CT for assessment of instability.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Fluoroscopy Knee There is no recent evidence supporting the routine use of fluoroscopy for the assessment of aseptic loosening, osteolysis, or instability. Fluoroscopy may be useful to see lucent lines in profile that could be obscured on standard AP radiographs [20,129,130] and can also be useful for demonstrating loosening under real-time manipulation. It can be useful in optimally positioning the joint for detection of radiographic osteolysis [129,130] and facilitates dynamic assessment of the knee under stress. In older studies, this procedure was determined to be useful, but it has been supplanted by other modalities and is now infrequently performed. MRI Knee Without and With IV Contrast MRI without and with IV contrast is not useful for assessment of osteolysis or instability. The use of IV contrast for assessing loosening has not been described. Imaging After Total Knee Arthroplasty MRI Knee Without IV Contrast The literature regarding MRI in the detection of implant loosening is evolving, and the available evidence supports its use. Using metal artifact reduction techniques, Fritz et al [93] described what they posited are distinct appearances for an intact periprosthetic interface (direct contact of the implant or cement with the surrounding bone), a periprosthetic fibrous membrane that indicates limited implant fixation that may or may not progress to loosening (1- to 2-mm thick layer with smooth margins surrounding the prosthesis along the bone interface) and frank bone resorption (a periprosthetic layer >2-mm thick with irregular margins). They reserve the use of the term loosening for cases in which MRI demonstrates circumferential osseous resorption together with signs of implant displacement, subsidence, or rotation. In a study of 116 knees in 114 patients that evaluated the interface type (normal, fibrous membrane, fluid, or osteolysis), percent integration (<33%, 33%-66%, or >66%), and presence of bone marrow edema.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. They determined MRI had higher sensitivity (84% versus 31%) but lower specificity (85% versus 96%) for patellar component loosening than did radiography [131]. MRI and CT have both been shown to be more sensitive for detection of osteolysis than radiographs [116]. MRI with metal artifact reduction techniques can detect osteolysis that is not visible on radiographs, even around the femoral component [96]. An MRI investigation of 11 TKA suspected of osteolysis on radiographs (and subsequently confirmed by surgery) found 10 cases with osteolysis at MRI and confirmed at surgery, 5 cases with additional osteolytic lesions detected on MRI, and 9 cases in which lesions were larger on MRI than on radiographs [97]. MRI can also show synovial changes due to particle disease before osteolytic lesions become apparent [22]. When effective, metal suppression can be used, and MRI can allow direct visualization of ligaments and tendons about the knee [93]. US Knee US has no significant role in assessing for aseptic prosthesis loosening and is not typically used for the assessment of osteolysis. US can be used to evaluate synovitis and soft tissues about the joint and to guide joint aspiration [132]. US is not typically used for assessment of instability but can be used to visualize and assess the medial and lateral collateral ligaments in the setting of TKA [133]. WBC Scan and Sulfur Colloid Scan Knee In-111 WBC, Tc-99m labeled WBC, and Tc-99m sulfur colloid knee scans are not useful for evaluation of aseptic knee prosthetic loosening. WBC/marrow studies are used to differentiate prosthetic loosening from acute infection and can be performed without or with a corresponding bone scan, the latter without altering the WBC/marrow results [127]. A negative WBC scan negates an acute neutrophilic infection but may be falsely negative in chronic infection [101].


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Love et al [109] reported WBC/marrow sensitivity, specificity, and accuracy as 96%, 87%, and 91%, respectively, for 150 total hip and knee replacements. Joseph et al [106] reported preoperative WBC/marrow imaging in 58 total hip and knee replacements with a sensitivity, specificity, and accuracy of 46%, 100%, and 88%, respectively. Palestro et al [107,134] described >90% accuracy and a specificity with a high sensitivity for WBC/marrow studies in the assessment of prosthetic joints. In the setting of chronic infection, differentiating chronic prosthetic infection from loosening can be more challenging, given that, in comparison with acute infections, chronic infections tend to have significantly fewer neutrophils, which are the predominant type of WBC labeled in an In-111 or Tc-99m-HMPAO WBC study, and radiolabeled WBCs are predominantly neutrophils. A decreased WBC sensitivity in osteomyelitis has also been attributed to a bacterial protective membrane or biofilm and to the effect of antibiotics [66]. Nonetheless, WBC/marrow scans to include SPECT/CT appear to be the imaging procedures of choice, with a high degree of accuracy for the failed joint prosthesis in the setting of a positive 3-phase bone scan because a negative WBC/marrow study does not include aseptic loosening [66]. In-111 WBC and Tc-99m sulfur colloid studies are not useful for assessment of instability. Variant 4: Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs. Periprosthetic fractures may occur either during or after surgery and can involve the femur, tibia, or patella. Among periprosthetic fractures, supracondylar distal femur fractures are most common, whereas patellar fractures are rare [135,136]. Supracondylar fractures occur in 0.3% to 2.5% of TKA, usually within 2 to 4 years after surgery, and often occur in the setting of low-energy trauma [136]. Tibial fractures are associated with loose components and malalignment.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Patellar fractures are associated with rheumatoid arthritis, steroid use, osteonecrosis, and malalignment. Most patients with periprosthetic fractures are elderly, having poor bone stock. Treatment depends Imaging After Total Knee Arthroplasty on fracture classification, which often includes information regarding fracture location, degree of comminution, and position and stability of the prosthesis. 3-Phase Bone Scan Knee Radionuclide 3-phase bone scans can demonstrate increased activity at a site of periprosthetic fracture and can show fractures that are radiographically occult [137,138]. In older osteopenic individuals with low rates of bone remodeling, it may take 48 to 72 hours for the development of increased radionuclide activity at the site of fracture. Within 1 to 2 years after prosthesis surgery, the differential diagnosis for increased periprosthetic activity would include postoperative change; however, with serial imaging, this postoperative activity should decrease over time, whereas activity increasing over time would be suggestive of a prosthetic complication, such as a periprosthetic fracture, aseptic loosening, or infection. Therefore, no conclusion should be drawn on an isolated bone scan unless it yields a normal study. CT Arthrography Knee There is no benefit to intraarticular contrast. CT Knee With IV Contrast IV contrast is not helpful for CT assessment of periprosthetic fracture. CT Knee Without and With IV Contrast IV contrast is not helpful for CT assessment of periprosthetic fracture. CT Knee Without IV Contrast Radiographically occult fractures may be detected on CT when metal artifact reduction techniques are used [20]. FDG-PET/CT Whole Body There is insufficient evidence to support the use of FDG-PET/CT for the assessment of periprosthetic fractures. Fluoride PET/CT Whole Body There is insufficient evidence to support the use of fluoride PET/CT for the assessment of periprosthetic fractures.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. Fluoroscopy Knee There is insufficient evidence to support the use of fluoroscopy for the assessment of periprosthetic fractures. MRI Knee Without and With IV Contrast IV contrast is not helpful for CT or MRI assessment of periprosthetic fracture. MRI Knee Without IV Contrast Radiographically occult fractures may be detected on MRI [22] when metal artifact reduction techniques are used. US Knee There is insufficient evidence to support the use of US for the assessment of periprosthetic fractures. WBC Scan and Sulfur Colloid Scan Knee There is insufficient evidence to support the use of In-111 WBC and Tc-99m sulfur colloid studies for the assessment of periprosthetic fractures. Variant 5: Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs. Malposition of femoral and tibial components may affect patellar alignment [139]. Excessive combined internal rotation of tibial and femoral components has been shown to be associated with patellar complications [139]. Moreover, Berger and Rubash [140] found that the amount of excessive combined internal rotation is directly proportional to the severity of patellofemoral complications. Abdelnasser et al [141] noted an internal rotation of the tibial component in TKA can lead to postoperative extension deficit. 3-Phase Bone Scan Knee There is insufficient evidence to support the use of bone scans for the assessment of rotational alignment of a TKA. CT Arthrography Knee Intraarticular contrast is not helpful in the CT assessment of rotational alignment. CT Knee With IV Contrast IV contrast is not helpful in the CT assessment of rotational alignment. Imaging After Total Knee Arthroplasty CT Knee Without and With IV Contrast IV contrast is not helpful in the CT assessment of rotational alignment.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. FDG-PET/CT Whole Body Stumpe et al [79] found diffuse synovial and focal extrasynovial FDG uptake in patients with component malrotation; however, FDG-PET/CT studies are not routinely used for the assessment of rotational alignment of a TKA. Fluoride PET/CT Whole Body There is insufficient evidence to support the use of fluoride PET/CT for the assessment of rotational alignment of a TKA. Fluoroscopy Knee There is insufficient evidence to support the use of fluoroscopy for the assessment of rotational alignment of a TKA. MRI Knee Without and With IV Contrast IV contrast is not useful for MRI assessment of rotational alignment. MRI Knee Without IV Contrast When adequate metal reduction techniques are used, MRI can be used to assess TKA component rotation [146]. Anatomic landmarks and axes required for measurement of rotational alignment parameters can be identified [147,148]. In a study of 50 patients with painful TKA and 16 controls, Murakami et al [148] found high interobserver agreement in all the relevant rotational alignment measurements and found statistically significant relative internal rotation of the femoral component in patients with a painful TKA. MRI literature is evolving, and the available evidence suggests MRI may be useful in the assessment of component rotation with adequate metal reduction techniques. US Knee There is insufficient evidence to support the use of US for the assessment of rotational alignment of a TKA. WBC Scan and Sulfur Colloid Scan Knee There is insufficient evidence to support the use of In-111 WBC and Tc-99m sulfur colloid studies for the assessment of rotational alignment of a TKA. Variant 6: Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy (quadriceps or patellar tendon tears, postoperative arthrofibrosis, patellar clunk syndrome, or impingement of nerves or other soft tissues). Additional imaging following radiographs.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. The incidence of quadriceps or patellar tendon tears after TKA is low, at 0.17% to 2.5% [149]. Sharkey et al [12] reported that the incidence of postoperative arthrofibrosis is also relatively low, accounting for 4.5% of failures in this series and 6.9% of failures where noted in the Lombardi et al [111] series. Of note, patients with keloids have increased odds risk of arthrofibrosis following primary TKA [150]. Additional periprosthetic soft-tissue causes of postoperative knee pain are also uncommon and include impingement of nerves or other soft tissues. Imaging After Total Knee Arthroplasty 3-Phase Bone Scan Knee There is insufficient evidence to support the use of 3-phase bone scan for the assessment of periprosthetic soft- tissue abnormalities. CT Arthrography Knee CT is not useful for assessment of periprosthetic soft-tissue abnormalities. Intraarticular contrast is not significantly helpful in the CT assessment of quadriceps or patellar tendon tears, postoperative arthrofibrosis, patellar clunk syndrome, or impingement of nerves or other soft tissues. CT Knee With IV Contrast CT is not useful for assessment of periprosthetic soft-tissue abnormalities. IV contrast is not significantly helpful in the CT assessment of quadriceps or patellar tendon tears, postoperative arthrofibrosis, patellar clunk syndrome, or impingement of nerves or other soft tissues. CT Knee Without and With IV Contrast CT is not useful for assessment of periprosthetic soft-tissue abnormalities. IV contrast is not significantly helpful in the CT assessment of quadriceps or patellar tendon tears, postoperative arthrofibrosis, patellar clunk syndrome, or impingement of nerves or other soft tissues. CT Knee Without IV Contrast There is insufficient evidence to support the use of CT without IV contrast for the assessment of periprosthetic soft- tissue abnormalities.


Imaging After Total Knee Arthroplasty

Imaging After Total Knee Arthroplasty. FDG-PET/CT Whole Body There is insufficient evidence to support the use of FDG-PET/CT for the assessment of periprosthetic soft-tissue abnormalities. Fluoride PET/CT Whole Body There is insufficient evidence to support the use of fluoride PET/CT for the assessment of periprosthetic soft-tissue abnormalities. Fluoroscopy Knee There is insufficient evidence to support the use of fluoroscopy for the assessment of periprosthetic soft-tissue abnormalities. MRI Knee Without IV Contrast MRI that uses robust metal reduction techniques can be used for evaluation of quadriceps or patellar tendinopathy in patients with TKA [152] and for evaluation of arthrofibrosis [93]. MRI can also demonstrate suprapatellar arthrofibrosis that can be associated with post TKA patellar clunk syndrome [147]. The presence of MRI measurable abundant thick fibrotic tissue in patients with a clinical diagnosis of knee fibrosis is of benefit to knee surgeons faced with patients with stiff TKA and can facilitate the decision to debride the knee, restore range of motion, and revise the implant [153]. MRI is beneficial for the workup of periarticular soft-tissue masses, including neoplastic masses and inflammatory pseudotumors [154]. US Knee US can be used for evaluation of quadriceps or patellar tendinopathy [155-157], postsurgical arthrofibrosis [158], and periarticular soft-tissue masses in patients with TKA. One review discusses the use of dynamic US to look for causes of snapping knee, including patellar clunk, snapping popliteus, and snapping related to component/liner malposition [159]. A case report discussed the utility of using dynamic US for the workup of patellar clunk syndrome [160]. WBC Scan and Sulfur Colloid Scan Knee There is insufficient evidence to support the use of In-111 WBC and Tc-99m sulfur colloid studies for the assessment of periprosthetic soft-tissue abnormalities.


Head Trauma Child PCAs

Head Trauma Child PCAs.  Introduction/Background Head trauma is a common indication for cranial imaging in children. Although traumatic brain injury is a leading cause of death and disability in children [1], the vast majority of head injuries are uncomplicated, transient, and do not require intervention [2]. The necessity of identifying clinically relevant, potentially treatable injury must be weighed against the risks of performing unwarranted imaging studies, possible unnecessary sedation, and inappropriate resource utilization. The precise criteria for minor head injury are not consistent in the literature, but this usually refers to a patient with normal or near-normal postevent mental status and is often defined by a Glasgow Coma Scale (GCS) of 14 or 15 [3]. The probability of significant anatomic injury in minor head trauma is low. Approximately 3% to 5% of children with minor head trauma have identifiable abnormalities by imaging but typically less than 1% requires neurosurgical intervention [4-7]. 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 Head Trauma-Child injury but resulted in a relatively high rate of CTs [13]. Additional smaller validation trials in the United States and abroad have also determined the PECARN criteria for very low risk criteria to be 100% sensitive [14-17].


Head Trauma Child PCAs

Head Trauma Child PCAs. Although precise comparison among the clinical decision rules is limited by differences in methodology and outcomes, the PECARN criteria remain the most widely validated, particularly for very young children, because of the high sensitivity and strong validation; the PECARN guidelines have been incorporated into the clinical variants for acute minor pediatric head trauma imaging. The PECARN criteria are summarized in Appendix 1. MRI The identification of small bleeds, particularly in the posterior fossa or brainstem, is further increased with hemesensitive techniques such as susceptibility-weighted imaging [2,24-26]. Diffusion-weighted imaging can be helpful in identifying nonhemorrhagic injuries and associated ischemia as well [27]. Standard MRI sequences have a low sensitivity for skull fractures. In recent years, limited rapid brain MRI techniques have been investigated as a means to evaluate pediatric head trauma without the need for sedation. Preliminary data suggest variations of this method may be helpful in following known intracranial hemorrhage documented by CT, but the sensitivity of rapid MRI in lieu of CT remains uncertain [28-31]. Additionally, there is no single uniform definition for rapid brain MRI techniques, and protocols vary among institutions. This is a rapidly evolving area of investigation but, at this time, there is no distinct procedural assignment for fast brain MRI in the ACR lexicon. Ultrasound A few recent studies in children have suggested ultrasound (US) can detect calvarial fractures with a sensitivity close to that of CT [32]. However, even in infants with open fontanelles, in which US imaging of the brain is possible, US lacks sensitivity for small subdural hematomas, particularly in the posterior fossa, as well as other small extra-axial hemorrhages.


Head Trauma Child PCAs

Head Trauma Child PCAs. Because intracranial injury can occur with or without fractures and US does not have a high sensitivity for hemorrhages, it does not currently have a significant role in head trauma imaging and as such is not considered in these variant procedures. Discussion of Procedures by Variant Variant 1: Child. Minor acute blunt head trauma. Very low risk for clinically important brain injury per PECARN criteria. Excluding suspected abusive head trauma. Initial imaging. Radiography Skull Not all skull fractures are evident by radiographs, and up to 50% of intracranial injuries in children occur in the absence of fracture [2,33]. Therefore, radiographs are not sufficient to evaluate for traumatic injury [9]. Head Trauma-Child CTA Head There is no relevant literature or expert consensus supporting the use of CT angiography (CTA) in the initial evaluation of children with minor trauma and very low risk for intracranial injury. MRI Head There is no relevant literature or expert consensus supporting the use of MRI in the initial evaluation of children with minor trauma and very low risk for intracranial injury. MRA Head There is no relevant literature or expert consensus supporting the use of MR angiography (MRA) in the initial evaluation of children with minor trauma and very low risk for intracranial injury. Arteriography Cerebral There is no relevant literature or expert consensus supporting the use of conventional cerebral angiography in the initial evaluation of children with minor trauma and very low risk for intracranial injury. Variant 2: Child. Minor acute blunt head trauma. Intermediate risk for clinically important brain injury per PECARN criteria. Excluding suspected abusive head trauma. Initial imaging. Radiography Skull Not all skull fractures are evident by radiographs, and up to 50% of intracranial injuries in children occur in the absence of fracture [2,33]. Therefore, radiographs are not sufficient to evaluate for traumatic injury [9].


Head Trauma Child PCAs

Head Trauma Child PCAs. CT may be considered in lieu of careful clinical observation in instances of parental preference, multiple risk factors, worsening clinical symptoms or signs during observation, and in young infants in which observational assessment is more challenging. Head Trauma-Child CTA Head There is no relevant literature or expert consensus supporting the use of CTA in the initial evaluation of children with minor head injury and intermediate risk for intracranial injury. MRI Head MRI is sensitive for acute intracranial hemorrhage and other intracranial traumatic injury. However, MRI in the acute setting is frequently impractical. The examination requires preimaging safety screening, is significantly longer than CT, and younger children often need sedation to compete the examination, further delaying time to imaging. IV contrast is typically of little use in evaluation of acute trauma. MRA Head There is no relevant literature or expert consensus supporting the use of MRA in the initial evaluation of children with minor head injury and intermediate risk for intracranial injury. Arteriography Cerebral There is no relevant literature or expert consensus supporting the use of conventional cerebral angiography in the initial evaluation of children with minor head injury and intermediate risk for intracranial injury. Variant 3: Child. Minor acute blunt head trauma. High risk for clinically important brain injury per PECARN criteria. Excluding suspected abusive head trauma. Initial imaging. Radiography Skull Not all skull fractures are evident by radiographs, and up to 50% of intracranial injuries in children occur in the absence of fracture [2,33]. Therefore, radiographs are not sufficient to evaluate for traumatic injury [9]. High-risk factors for intracranial injury from minor head trauma in children <2 years of age by PECARN criteria include those with a GCS of 14, other signs of altered mental status, or signs of any palpable skull fracture.


Head Trauma Child PCAs

Head Trauma Child PCAs. The risk of clinically significant intracranial injury in these patients is estimated at approximately 4.4% [5]. Although still relatively uncommon, the risk of interveneable injury is substantial enough that imaging is strongly recommended. CT has the advantage of rapid acquisition and excellent sensitivity for acute intracranial hemorrhage and fractures. CTA Head Most vascular injuries in children are cervical, and there remains a relative paucity of evidence-based literature regarding the prevalence and nature of isolated intracranial vascular injury in pediatric head trauma. Intracranial vascular injuries have been reported in children with minor head trauma but are likely uncommon [19,34,35]. Vascular imaging is usually not a standard component of initial first-line imaging evaluation in patients with minor head trauma. However, if there are clinical symptoms or signs on other imaging raising suspicion for vascular injury, such as basilar fracture through a vascular canal, CTA may be considered for rapid assessment in the acute setting. MRI Head MRI is sensitive for acute intracranial hemorrhage and other intracranial traumatic injuries. However, MRI in the emergent setting is frequently impractical. The examination is typically significantly longer than CT, requires safety screening, results take longer to obtain, and younger children often need sedation to complete the examination, further delaying assessment. IV contrast is typically of little use in evaluation of acute trauma. MRA Head There remains a relative paucity of evidence-based literature regarding the prevalence and nature of vascular injury in minor pediatric head trauma. Vascular injuries have been reported in children with minor head trauma but are likely uncommon [19,34,35]. Vascular imaging is generally not a standard component of initial first-line imaging evaluation in patients with minor head trauma. If there are clinical or other imaging signs suggestive of vascular injury, MRA could be considered.


Head Trauma Child PCAs

Head Trauma Child PCAs. MRA can be performed without IV contrast using time-of-flight sequences, although IV contrast may be helpful for clarification in some instances, particularly when imaging is limited by tortuosity or flow artifact. Head Trauma-Child Variant 4: Child. Moderate or severe acute blunt head trauma (GCS less than or equal to 13). Excluding suspected abusive head trauma. Initial imaging. Radiography Skull Not all skull fractures are evident by radiographs, and up to 50% of intracranial injuries in children occur in the absence of fracture [2,33]. Therefore, radiographs are not sufficient to evaluate for traumatic injury [9]. CT Head Moderate and severe head injury is typically associated with post-traumatic mental status changes. Despite the lower incidence and fewer numbers of studies addressing more significant injury in children, there is little debate regarding the need for imaging because of the greater incidence of intracranial injury in patients with decreased GCS [36]. CT has the advantage of rapid acquisition and excellent sensitivity for traumatic injuries, such as herniation or hemorrhage, which benefit from prompt intervention. CTA Head Imaging for vascular injury is primarily guided by clinical suspicion or imaging findings, such as fracture through the skull base or vascular channels. Most literature regarding vascular injury in the pediatric population is confined to small series, and the true incidence and natural history of these injuries in children remains uncertain [19]. However, vascular imaging should be considered in patients with evidence of arterial stroke by examination or by imaging as well as those with fractures extending through the skull base or vascular channels, which are typically encountered in higher impact traumas [37,38]. CTA provides high spatial resolution and rapid assessment for vascular injuries.


Head Trauma Child PCAs

Head Trauma Child PCAs. MRI Head Patients with more significant trauma and lower GCS are more likely to have sustained shear injury or ischemia, and MRI may have a higher yield for prognosis in this instance [25,39]. However, because of the time required to arrange and perform the examination and possible need for sedation, MRI can be difficult to accomplish emergently and should not delay evaluation. IV contrast is typically of little use in evaluation of acute trauma. MRA Head MRA can evaluate the intracranial vasculature and can be performed in conjunction with MRI when vascular injury is clinically suspected. However, as with standard MRI, this examination may be difficult to perform emergently. MRA can be performed without contrast using time-of-flight sequences, although IV contrast may be helpful for clarification in some instances, particularly when imaging is limited by tortuosity or flow artifact. Arteriography Cerebral Conventional cerebral angiography remains the definitive diagnostic test for vascular injury and can demonstrate subtle abnormalities that may be occult on either CTA or MRA. However, because of the invasive procedure and need for sedation, conventional angiography should be reserved for problem solving in cases with uncertain noninvasive imaging and high clinical suspicion of vascular injury. Variant 5: Child. Subacute blunt head trauma with cognitive or neurologic signs. The exact definition of subacute injury varies, but subacute head injury is typically defined as occurring between 8 days and 1 month after the initial traumatic event [40,41]. Injury may be caused by secondary processes, such as herniation from worsening parenchymal edema, ischemia, hydrocephalus, and progressive or delayed hemorrhage. During the subacute phase, up to 30% of contusions may cause worsening mass effect with edema from toxic metabolites released into the surrounding tissue and cerebral autoregulation dysfunction [42].


Head Trauma Child PCAs

Head Trauma Child PCAs. Radiography Skull There is no relevant literature or expert consensus regarding the use of skull radiographs in children with subacute head trauma and cognitive or neurologic signs. CT Head Patients with a significant change in neurologic status are at a high risk for progressive intracranial injury, may require neurosurgical intervention, and may benefit from imaging [43]. CT can provide rapid, accurate assessment for progressive hemorrhage, herniation, and hydrocephalus. In one study of 116 children with CT positive for Head Trauma-Child traumatic head injury, 9 patients experienced neurologic deterioration, 6 of whom required neurosurgery [44]. However, all patients undergoing intervention were identified clinically, without imaging, reflecting the importance of clinical examination in this population. CTA Head Imaging for vascular injury is primarily guided by clinical suspicion. Most literature regarding vascular injury in the pediatric population is confined to small series, and the true incidence and natural history of these injuries in children remains uncertain [19]. However, vascular imaging should be considered in patients with evidence of arterial stroke by examination or by imaging as well as those with fractures extending through the skull base vascular channels [37]. CTA provides high spatial resolution and rapid assessment for vascular injury. MRI Head MRI may be helpful in evaluating persistent, unexplained, or new neurological deficits in the subacute setting. MRI has a high sensitivity for blood products, including small brainstem and infratentorial hemorrhages as well as subacute hemorrhage, which becomes less dense on CT over time. The superior detection of nonhemorrhagic contusions and ischemia may be particularly helpful in the absence of findings on prior CT [38]. However, a standard MRI requires the patient be stable enough to tolerate a lengthier examination.


Head Trauma Child PCAs

Head Trauma Child PCAs. In recent years, limited rapid MRI techniques have been investigated as a means to evaluate pediatric head trauma without the need for sedation. Preliminary data suggest variations of this method may be helpful in following known intracranial hemorrhage documented by CT, but the sensitivity of rapid MRI in lieu of CT remains uncertain [28-31]. Contrast-enhanced sequences are generally not indicated unless there is a concern for infection, such as from penetrating injury or fractures involving the sinuses. MRA Head MRA can evaluate the intracranial vasculature and can be performed in conjunction with MRI when vascular injury is clinically suspected. However, as with standard MRI, it may be difficult to perform emergently. MRA can be performed without IV contrast using time-of-flight sequences, although IV contrast may be helpful for clarification in some instances, particularly when imaging is limited by tortuosity or flow artifact. Arteriography Cerebral Conventional cerebral angiography remains the definitive diagnostic test for vascular injury and can demonstrate subtle abnormalities that may be occult on either CTA or MRA. However, because of the invasive procedure and need for sedation, conventional angiography should be reserved for problem solving in cases with uncertain noninvasive imaging and high clinical suspicion of injury. Variant 6: Child. Chronic blunt head trauma with new or progressive cognitive or neurologic deficits. Excluding suspected abusive head trauma and post-traumatic seizure. Postconcussion symptoms are common after head injury. In mild traumatic cases, imaging in the chronic setting is usually negative, and in cases in which more severe trauma or prior intracranial injury has occurred, imaging in the chronic period rarely reveals additional actionable changes [45-47]. CT Head There are little data regarding the use of CT in children in the chronic post-traumatic setting.


Head Trauma Child PCAs

Head Trauma Child PCAs. A few studies addressing CT is this setting support a low diagnostic yield for imaging in the post-traumatic setting [46,47]. One study of 52 children with chronic head injury demonstrated CTs performed on only 8 patients [46]. One patient was found to have a fracture. No intracranial injury was detected. CT has limited sensitivity for nonacute intracranial hemorrhage and small contusions. CT likely has little role in evaluating most children with chronic head injury but may be a consideration when results are needed quickly. Head Trauma-Child CTA Head Although late post-traumatic vascular complications, such as pseudoaneurysm, can occur, there is no substantial literature or expert consensus supporting the use of CTA in children in chronic traumatic injury. Imaging for vascular injury is primarily guided by clinical suspicion or imaging findings, such as fracture through the skull base or vascular channels. In these instances, CTA provides high spatial resolution and rapid assessment for vascular injury. MRA Head Although late post-traumatic vascular complications, such as pseudoaneurysm, can occur, there is no substantial literature or expert consensus supporting the use of MRA in children in chronic traumatic injury. Imaging for vascular injury is primarily guided by clinical suspicion or imaging findings, such as fracture through the skull base or vascular channels. MRA can be performed without IV contrast using time-of-flight sequences, although contrast may be helpful for clarification in some instances, particularly when imaging is limited by tortuosity or flow artifact. Arteriography Cerebral There is no relevant literature or expert consensus regarding the use of conventional cerebral angiography in evaluating children with chronic head trauma. FDG-PET/CT Brain There is no relevant literature or expert consensus regarding the use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT of the brain in evaluating children with chronic head trauma.


Head Trauma Child PCAs

Head Trauma Child PCAs. MR Spectroscopy Head There have been few studies investigating spectroscopic changes in the brain of children with prior head trauma. Some preliminary data suggest there may be reduced N-acetyl aspartate metabolites in the corpus callosum in these children [50]. However, these studies are limited by patient selection and very small sample size, and the clinical relevance of these findings in children is unclear. MRI Head without IV Contrast with DTI There have been a few studies suggesting that post-traumatic microstructural changes in the white matter can be identified with diffusion-tensor imaging (DTI). However, these studies are usually in older adolescents and young adults, and the data remain limited by small sample sizes in select populations. There are little data regarding the routine use of this technique in children. MRI Functional (fMRI) Head without IV Contrast Some preliminary work suggests that changes in connectivity in pediatric patients may correlate with postconcussion symptoms [51,52]. However, studies are limited by small, select sample sizes, and there remains no strong literature to support the routine use of functional MRI (fMRI) in evaluation of post-traumatic head injury. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www. acr.org/ac. Appropriateness Category Names and Definitions Relative Radiation Level Information Potential adverse health effects associated with radiation exposure are an important factor to consider when selecting the appropriate imaging procedure. Because there is a wide range of radiation exposures associated with different diagnostic procedures, a relative radiation level (RRL) indication has been included for each imaging


Nonischemic Myocardial Disease with Clinical Manifestations Ischemic Cardiomyopathy Already Excluded .  Introduction/Background Nonischemic cardiomyopathies (NICMs) encompass a broad spectrum of disorders of the myocardium associated with mechanical or electrical dysfunction leading to inappropriate ventricular hypertrophy or dilation, without evidence of ischemia [1]. Generally, valvular, hypertensive, and congenital diseases are treated separately from the NICM discussed here. The myocardial involvement can be either primary (genetic, acquired, or mixed) or secondary to a systemic disease process [2]. NICM can also be classified into distinct morphological and functional types, each of which can be subclassified as familial or nonfamilial types [3]. In this document, we have adapted this classification with five variants of nonischemic myocardial diseases: 1) hypertrophic cardiomyopathy (HCM); 2) restrictive cardiomyopathy or infiltrative diseases; 3) dilated cardiomyopathy (DCM) or unclassified cardiomyopathy; 4) arrhythmogenic cardiomyopathy (arrhythmia of ventricular origin); and 5) inflammatory cardiomyopathy [2]. With increasing availability and use of genetics, it is now known that cardiomyopathies do not fit into specific morphological and functional phenotypes as discussed above, and there is tremendous genetic heterogeneity. The recently proposed MOGE(S) nosology system provides a more comprehensive classification of cardiomyopathies, describing the morphofunctional phenotype (M), organ (O), genetic inheritance pattern (G), etiological annotation (E), and functional status (S) [4]. NICM has an approximate prevalence of 0.02% with an annual death rate of 25,000 in the United States [2]. In adults, the prevalence of HCM is 1:250 to 500, DCM is 1:250 to 500, and arrhythmogenic right ventricular cardiomyopathy (ARVD) is 1:2,000 to 5,000 [5], whereas these are uncommon in children. Clinical presentation is variable, including heart failure (HF), arrhythmia, sudden death, and acute chest pain.


Nonischemic Myocardial Disease with Clinical Manifestations Ischemic Cardiomyopathy Already Excluded . Common presentations include dyspnea, edema, ascites, chest discomfort palpitations, and syncope. In patients with clinical HF, a primary cardiomyopathy is diagnosed in 2% to 15% of patients, whereas in some large-scale trials, patients with nonischemic HF accounted for 18% to 53% of the study population [6]. Acute presentation with chest pain, elevated cardiac enzymes, and abnormal electrocardiogram (ECG) may be seen inflammatory cardiomyopathies. Unlike ischemic cardiomyopathy, the pathophysiology of NICM is usually unclear and multifactorial, the functional consequences are global, the prognosis is better, and the therapeutic response is different [2]. The primary role of imaging in NICM is to characterize the disease and establish the specific etiology, which is essential for determining optimal management. Although patients with NICM require general treatment for HF or arrhythmia, therapy is often tailored, depending on the etiology. For example, iron-overload cardiomyopathy is aMayo Clinic, Rochester, Minnesota. bPanel Chair, Cleveland Clinic Florida, Weston, Florida. cPanel Vice-Chair, Cleveland Clinic, Cleveland, Ohio. dMiami Cardiac and Vascular Institute and Baptist Health of South Florida, Miami, Florida. eUniversity of Utah, Department of Radiology and Imaging Sciences, Salt Lake City, Utah. fUniversity of Wisconsin, Madison, Wisconsin. gUniversity of Iowa Hospitals and Clinics, Iowa City, Iowa. hToronto General Hospital, University of Toronto, Toronto, Ontario, Canada. iThe Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada. jQueen's University, Kingston, Ontario, Canada; Cardiology expert. kNorthwestern University Feinberg School of Medicine, Chicago, Illinois; Society for Cardiovascular Magnetic Resonance. lUniversity of Alabama at Birmingham, Birmingham, Alabama. mUniversity of Virginia Health System, Charlottesville, Virginia; Society of Cardiovascular Computed Tomography.