The Role of Imaging for Gastrointestinal Bleeding: Consensus Recommendations From the American College of Gastroenterology and Society of Abdominal Radiology.

Gastrointestinal (GI) bleeding is the most common GI diagnosis leading to hospitalization within the United States. Prompt diagnosis and treatment of GI bleeding is critical to improving patient outcomes and reducing high healthcare utilization and costs. Radiologic techniques including computed tomography angiography, catheter angiography, computed tomography enterography, magnetic resonance enterography, nuclear medicine red blood cell scan, and technetium-99m pertechnetate scintigraphy (Meckel scan) are frequently used to evaluate patients with GI bleeding and are complementary to GI endoscopy. However, multiple management guidelines exist which differ in the recommended utilization of these radiologic examinations. This variability can lead to confusion as to how these tests should be used in the evaluation of GI bleeding. In this document, a panel of experts from the American College of Gastroenterology and Society of Abdominal Radiology provide a review of the radiologic examinations used to evaluate for GI bleeding including nomenclature, technique, performance, advantages, and limitations. A comparison of advantages and limitations relative to endoscopic examinations is also included. Finally, consensus statements and recommendations on technical parameters and utilization of radiologic techniques for GI bleeding are provided.

The Role of Imaging for GI Bleeding: ACG and SAR Consensus Recommendations.

Gastrointestinal (GI) bleeding is the most common GI diagnosis leading to hospitalization within the United States. Prompt diagnosis and treatment of GI bleeding is critical to improving patient outcomes and reducing high health care utilization and costs. Radiologic techniques including CT angiography, catheter angiography, CT enterography, MR enterography, nuclear medicine red blood cell scan, and technetium-99m pertechnetate scintigraphy (Meckel scan) are frequently used to evaluate patients with GI bleeding and are complementary to GI endoscopy. However, multiple management guidelines exist, which differ in the recommended utilization of these radiologic examinations. This variability can lead to confusion as to how these tests should be used in the evaluation of GI bleeding. In this document, a panel of experts from the American College of Gastroenterology and Society of Abdominal Radiology provide a review of the radiologic examinations used to evaluate for GI bleeding including nomenclature, technique, performance, advantages, and limitations. A comparison of advantages and limitations relative to endoscopic examinations is also included. Finally, consensus statements and recommendations on technical parameters and utilization of radiologic techniques for GI bleeding are provided. © Radiological Society of North America and the American College of Gastroenterology, 2024. Supplemental material is available for this article. This article is being published concurrently in American Journal of Gastroenterology and Radiology. The articles are identical except for minor stylistic and spelling differences in keeping with each journal's style. Citations from either journal can be used when citing this article. See also the editorial by Lockhart in this issue.

Beta-Catenin-Mutated Hepatocellular Adenomas at Hepatobiliary Phase MRI: A Systematic Review and Meta-Analysis.

BACKGROUND: Beta-catenin-mutated hepatocellular adenomas (ß-HCAs) can appear iso- to hyperintense at the hepatobiliary phase (HBP) at magnetic resonance imaging (MRI). Given the relatively lower prevalence of ß-HCAs, prior studies had limited power to show statistically significant differences in the HBP signal intensity between different subtypes. PURPOSE: To assess the diagnostic performance of HBP MRI to discriminate ß-HCA from other subtypes. STUDY TYPE: Systemic review and meta-analysis. POPULATION: Ten original studies were included, yielding 266 patients with 397 HCAs (9%, 36/397 ß-HCAs and 91%, 361/397 non-ß-HCAs). FIELD STRENGTH/SEQUENCE: 1.5 T and 3.0 T, HBP. ASSESSMENT: PubMed, Web of Science, and Embase databases were searched from January 1, 2000, to August 31, 2023, for all articles reporting HBP signal intensity in patients with histopathologically proven HCA subtypes. QUADAS-2 was used to assess risk of bias and concerns regarding applicability. STATISTICAL TESTS: Univariate random-effects model was used to calculate pooled estimates. Heterogeneity estimates were assessed with I2 heterogeneity index. Meta-regression (mixed-effect model) was used to test for differences in the prevalence of HBP signal between HCA groups. The threshold for statistical significance was set at P < 0.05. RESULTS: HBP iso- to hyperintensity was associated with ß-HCAs (pooled prevalence was 72.3% in ß-HCAs and 6.3% in non-ß-HCAs). Pooled sensitivity and specificity were 72.3% (95% confidence interval 54.1-85.3) and 93.7% (93.8-97.7), respectively. Specificity had substantial heterogeneity with I2 of 83% due to one study, but not for sensitivity (I2 = 0). After excluding this study, pooled sensitivity and specificity were 77.4% (59.6-88.8) and 94.1% (88.9-96.9), with no substantial heterogeneity. One study had high risk of bias for patient selection and two studies were rated unclear for two domains. DATA CONCLUSION: Iso- to hyperintensity at HBP MRI may help to distinguish ß-HCA subtype from other HCAs with high specificity. However, there was heterogeneity in the pooled estimates. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY: Stage 2.

Diagnostic performance of CT/MRI LI-RADS v2018 in non-cirrhotic steatotic liver disease.

OBJECTIVE: To assess the performance of computed tomography (CT)/magnetic resonance imaging (MRI) Liver Imaging Reporting and Data System (LI-RADS) among patients with non-cirrhotic steatotic liver disease (SLD). MATERIALS AND METHODS: This IRB-approved, retrospective study included 119 observations from 77 adult patients (36 women, 41 men; median 64 years) who underwent liver CT or MRI from 2010 to 2023. All patients had histopathologic evidence of SLD without cirrhosis. Three board-certified abdominal radiologists blinded to tissue diagnosis and imaging follow-up assessed observations with LI-RADS. The positive predictive value (PPV), sensitivity, specificity, accuracy, and inter-reader agreement were calculated. RESULTS: Seventy-five observations (63%) were benign and 44 (37%) were malignant. PPV for hepatocellular carcinoma (HCC) was 0-0% for LR-1, 0-0% for LR-2, 0-7% for LR-3, 11-20% for LR-4, 75-88% for LR-5, 0-8% for LR-M, and 50-75% for LR-TIV. For LR-5 in identifying HCC, sensitivity was 79-83%, specificity was 91-97%, and accuracy was 89-92%. For composite categories of LR-5, LR-M, or LR-TIV in identifying malignancy, sensitivity was 86-89%, specificity was 85-96%, and accuracy was 86-93%. The most common false positives for LR-5 were hepatocellular adenomas. Only 59-65% of HCCs showed non-peripheral washout at CT versus 67-83% at MRI, though nearly all had an enhancing capsule. PPV and accuracy of LR-5 for HCC did not differ by modality. Inter-reader agreement for major features ranged from 0.667 to 0.830 and was 0.766 for the final category. CONCLUSION: Despite challenges such as the lower prevalence of non-peripheral washout at CT and overlapping imaging features between HCC and hepatocellular adenomas, LI-RADS may serve as an effective tool in assessing focal liver lesions in SLD. CLINICAL RELEVANCE STATEMENT: LI-RADS in non-cirrhotic steatotic liver disease can effectively diagnose hepatocellular carcinoma and malignancy at computed tomography and magnetic resonance imaging, thereby guiding clinical management decisions and expediting patient care pathways. KEY POINTS: Performance of LI-RADS is unknown in non-cirrhotic patients with steatotic liver disease. LI-RADS 5 category showed a high pooled specificity of 91-97% for hepatocellular carcinoma. LI-RADS can non-invasively risk stratify focal liver observations in non-cirrhotic patients with steatotic liver disease.

MRI with DWI improves detection of liver metastasis and selection of surgical candidates with pancreatic cancer: a systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review and meta-analysis to evaluate if magnetic resonance imaging (MRI) with diffusion weighted imaging (DWI) adds value compared to contrast-enhanced computed tomography (CECT) alone in the preoperative evaluation of pancreatic cancer. METHODS: MEDLINE, EMBASE, and Cochrane databases were searched for relevant published studies through October 2022. Studies met eligibility criteria if they evaluated the per-patient diagnostic performance of MRI with DWI in the preoperative evaluation of newly diagnosed pancreatic cancer compared to CECT. Our primary outcome was the number needed to treat (NNT) to prevent one futile surgery using MRI with DWI, defined as those in which CECT was negative and MRI with DWI was positive for liver metastasis (i.e., surgical intervention in metastatic disease missed by CECT). The secondary outcomes were to determine the diagnostic performance and the NNT of MRI with DWI to change management in pancreatic cancer. RESULTS: Nine studies met the inclusion criteria with a total of 1121 patients, of whom 172 had liver metastasis (15.3%). The proportion of futile surgeries reduced by MRI with DWI was 6.0% (95% CI, 3.0-11.6%), yielding an NNT of 16.6. The proportion of cases that MRI with DWI changed management was 18.1% (95% CI, 9.9-30.7), corresponding to an NNT of 5.5. The per-patient sensitivity and specificity of MRI were 92.4% (95% CI, 87.4-95.6%) and 97.3% (95% CI, 96.0-98.1). CONCLUSION: MRI with DWI may prevent futile surgeries in pancreatic cancer by improving the detection of occult liver metastasis on preoperative CECT with an NNT of 16.6. CLINICAL RELEVANCE STATEMENT: MRI with DWI complements the standard preoperative CECT evaluation for liver metastasis in pancreatic cancer, improving the selection of surgical candidates and preventing unnecessary surgeries. KEY POINTS: • The NNT of MRI with DWI to prevent potential futile surgeries due to occult liver metastasis on CECT, defined as those in which CECT was negative and MRI with DWI was positive for liver metastasis, in patients with pancreatic cancer was 16.6. • The higher performance of MRI with DWI to detect liver metastasis occult on CECT can be attributed to an increased detection of subcentimeter liver metastasis.

Computed tomography versus ultrasound for the diagnosis of acute cholecystitis: a systematic review and meta-analysis.

OBJECTIVES: Some patients undergo both computed tomography (CT) and ultrasound (US) sequentially as part of the same evaluation for acute cholecystitis (AC). Our goal was to perform a systematic review and meta-analysis comparing the diagnostic performance of US and CT in the diagnosis of AC. MATERIALS AND METHODS: Databases were searched for relevant published studies through November 2023. The primary objective was to compare the head-to-head performance of US and CT using surgical intervention or clinical follow-up as the reference standard. For the secondary analysis, all individual US and CT studies were analyzed. The pooled sensitivities, specificities, and areas under the curve (AUCs) were determined along with 95% confidence intervals (CIs). The prevalence of imaging findings was also evaluated. RESULTS: Sixty-four studies met the inclusion criteria. In the primary analysis of head-to-head studies (n = 5), CT had a pooled sensitivity of 83.9% (95% CI, 78.4-88.2%) versus 79.0% (95% CI, 68.8-86.6%) of US (p = 0.44). The pooled specificity of CT was 94% (95% CI, 82.0-98.0%) versus 93.6% (95% CI, 79.4-98.2%) of US (p = 0.85). The concordance of positive or negative test between both modalities was 82.3% (95% CI, 72.1-89.4%). US and CT led to a positive change in management in only 4 to 8% of cases, respectively, when ordered sequentially after the other test. CONCLUSION: The diagnostic performance of CT is comparable to US for the diagnosis of acute cholecystitis, with a high rate of concordance between the two modalities. CLINICAL RELEVANCE STATEMENT: A subsequent US after a positive or negative CT for suspected acute cholecystitis may be unnecessary in most cases. KEY POINTS: When there is clinical suspicion of acute cholecystitis, patients will often undergo both CT and US. CT has similar sensitivity and specificity compared to US for the diagnosis of acute cholecystitis. The concordance rate between CT and US for the diagnosis of acute cholecystitis is 82.3%.

Accuracy of volumetric bone mineral density measurement in weight bearing, cone beam computed tomography.

BACKGROUND: Weight bearing computed tomography (WBCT) utilizes cone beam CT technology to provide assessments of lower limb joint structures while they are functionally loaded. Grey-scale values indicative of X-ray attenuation that are output from cone beam CT are challenging to calibrate, and their use for bone mineral density (BMD) measurement remains debatable. To determine whether WBCT can be reliably used for cortical and trabecular BMD assessment, we sought to establish the accuracy of BMD measurements at the knee using modern WBCT by comparing them to measurements from conventional CT. METHODS: A hydroxyapatite phantom with three inserts of varying densities was used to systematically quantify signal uniformity and BMD accuracy across the acquisition volume. We evaluated BMD in vivo (n = 5, female) using synchronous and asynchronous calibration techniques in WBCT and CT. To account for variation in attenuation along the height (z-axis) of acquisition volumes, we tested a height-dependent calibration approach for both WBCT and CT images. RESULTS: Phantom BMD measurement error in WBCT was as high as 15.3% and consistently larger than CT (up to 5.6%). Phantom BMD measures made under synchronous conditions in WBCT improved measurement accuracy by up to 3% but introduced more variability in measured BMD. We found strong correlations (R = 0.96) as well as wide limits of agreement (-324 mgHA/cm3 to 183 mgHA/cm3) from Bland-Altman analysis between WBCT and CT measures in vivo that were not improved by height-dependent calibration. CONCLUSION: Whilst BMD accuracy from WBCT was found to be dependent on apparent density, accuracy was independent of the calibration technique (synchronous or asynchronous) and the location of the measurement site within the field of view. Overall, we found strong correlations between BMD measures from WBCT and CT and in vivo measures to be more accurate in trabecular bone regions. Importantly, WBCT can be used to distinguish between anatomically relevant differences in BMD, however future work is necessary to determine the repeatability and sensitivity of BMD measures in WBCT.

Analysis of Hand Joint Space Morphology in Women and Men with Hereditary Hemochromatosis.

Hereditary hemochromatosis (HH) causes unbalanced iron deposition in many organs including the joints leading to severe cartilage loss and bone damage in the metacarpophalangeal joints (MCPJ). High-resolution peripheral quantitative computed tomography (HR-pQCT) and its joint space width (JSW) quantification algorithm quantifies in vivo 3D joint morphology. We therefore aimed to (i) determine feasibility and performance of the JSW algorithm in HH, (ii) quantify joint space morphology, and (iii) investigate the relationship between morphological and clinical parameters in HH. Here, we performed an exploratory study on 24 HH patients and sex- and age-matched controls using HR-pQCT imaging of MCPJ. Mineralized bone structure was automatically segmented from the grayscale image data and periosteal surface bone masks and joint space masks were generated. Mean, minimal, and maximal joint space width (JSW; JSW.MIN; JSW.MAX), JSW heterogeneity (JSW.SD), JSW asymmetry (JSW.AS), and joint space volume (JSV) were computed. Demographics and, for HH patients, disease-specific parameters were recorded. Segmentation of JS was very good with 79.7% of MCPJs successfully segmented at first attempt and 20.3% requiring semi-manual correction. HH men showed larger JSV at all MCPs (+ 25.4% < JSV < + 41.8%, p < 0.05), larger JSW.MAX at MCP 3-4 (+ 14%, 0.006 < p < 0.062), and wider JSW (+ 13%, p = 0.043) at MCP 4 relative to HH women. Compared to controls, both HH men and HH women showed larger JSW.AS and smaller JSW.MIN at all MCP levels, reaching significance for HH men at MCP 2 and 3 (JSW.AS: + 323% < JSW.AS < + 359%, 0.020 < p < 0.043; JSW.MIN: - 216% < JSW.MIN < - 225%, p < 0.043), and for women at MCP 3 (JSW.AS: + 180%, p = 0.025; JSW.MIN: - 41.8%, p = 0.022). Time since HH diagnosis was correlated positively with MCP 4 JSW.AS and JSW.SD (0.463 < ρ < 0.499, p < 0.040), and the number of phlebotomies since diagnosis was correlated with JSW.SD at all MCPs (0.432 < ρ < 0.535, p < 0.050). HR-pQCT-based JSW quantification in MCPJ of HH patients is feasible, performs well even in narrow JS, and allows to define the microstructural joint burden of HH.

Proportion of malignancy in Bosniak classification of cystic renal masses version 2019 (v2019) classes: systematic review and meta-analysis.

OBJECTIVES: Determine the proportion of malignancy within Bosniak v2019 classes. METHODS: MEDLINE and EMBASE were searched. Eligible studies contained patients with cystic renal masses undergoing CT or MRI renal protocol examinations with pathology confirmation, applying Bosniak v2019. Proportion of malignancy was estimated within Bosniak v2019 class. Risk of bias was assessed using QUADAS-2. RESULTS: We included 471 patients with 480 cystic renal masses. No class I malignant masses were observed. Pooled proportion of malignancy were class II, 12% (6/51, 95% CI 5-24%); class IIF, 46% (37/85, 95% CI 28-66%); class III, 79% (138/173, 95% CI 68-88%); and class IV, 84% (114/135, 95% CI 77-90%). Proportion of malignancy differed between Bosniak v2019 II-IV classes (p = 0.004). Four studies reported the proportion of malignancy by wall/septa feature. The pooled proportion of malignancy with 95% CI were class III thick smooth wall/septa, 77% (41/56, 95% CI 53-91%); class III obtuse protrusion ≤ 3 mm (irregularity), 83% (97/117, 95% CI 75-89%); and class IV nodule with acute angulation, 86% (50/58, 95% CI 75-93%) or obtuse angulation ≥ 4 mm, 83%, (64/77, 95% CI 73-90%). Subgroup analysis by wall/septa feature was limited by sample size; however, no differences were found comparing class III masses with irregularity to class IV masses (p = 0.74) or between class IV masses by acute versus obtuse angles (p = 0.62). CONCLUSION: Preliminary data suggest Bosniak v2019 class IIF masses have higher proportion of malignancy compared to the original classification, controlling for pathologic reference standard. There are no differences in proportion of malignancy comparing class III masses with irregularities to class IV masses with acute or obtuse nodules. KEY POINTS: • The proportion of malignancy in Bosniak v2019 class IIF cystic masses is 46% (37 malignant/85 total IIF masses, 95% confidence intervals (CI) 28-66%). • The proportion of malignancy in Bosniak v2019 class III cystic masses is 79% (138/173, 95% CI 68-88%) and in Bosniak v2019 class IV cystic masses is 84% (114/135, 95% CI 77-90%). • Class III cystic masses with irregularities had similar proportion of malignancy (83%, 97/117, 95% CI 75-89%) compared to Bosniak class IV masses (84%, 114/135, 95% CI 77-90%) overall (p = 0.74) with no difference within class IV masses by acute versus obtuse angulation (p = 0.62).

Split scar sign to predict complete response in rectal cancer after neoadjuvant chemoradiotherapy: systematic review and meta-analysis.

OBJECTIVES: Magnetic resonance imaging (MRI) is the modality of choice for rectal cancer initial staging and restaging after neoadjuvant chemoradiation. Our objective was to perform a meta-analysis of the diagnostic performance of the split scar sign (SSS) on rectal MRI in predicting complete response after neoadjuvant therapy. METHODS: MEDLINE, EMBASE, and Cochrane databases were searched for relevant published studies through June 2023. Primary studies met eligibility criteria if they evaluated the diagnostic performance of the SSS to predict complete response on pathology or clinical follow-up in patients undergoing neoadjuvant chemoradiation. A meta-analysis with a random-effects model was used to estimate pooled sensitivity and specificity, area under the curve (AUC), and diagnostic odds ratio (DOR) of the SSS. RESULTS: A total of 4 studies comprising 377 patients met the inclusion criteria. The prevalence of complete response in the studies was 21.7-52.5%. The pooled sensitivity and specificity of the SSS to predict complete response were 62.0% (95% CI, 43.5-78.5%) and 91.9% (95% CI, 78.9-97.2%), respectively. The estimated AUC for SSS was 0.83 (95% CI, 0.56-0.94) with a DOR of 18.8 (95% CI, 3.65-96.5). CONCLUSION: The presence of SSS on rectal MRI demonstrated high specificity for complete response in patients with rectal cancer after neoadjuvant chemoradiation. This imaging pattern can be a valuable tool to identify potential candidates for organ-sparing treatment and surveillance. CLINICAL RELEVANCE STATEMENT: SSS presents high specificity for complete response post-neoadjuvant. This MRI finding enhances rectal cancer treatment assessment and aids clinicians and patients in choosing watch-and-wait over immediate surgery, which can potentially reduce costs and associated morbidity. KEY POINTS: •Fifteen to 50% of rectal cancer patients achieve complete response after neoadjuvant chemoradiation and may be eligible for a watch-and-wait strategy. •The split scar sign has high specificity for a complete response. •This imaging finding is valuable to select candidates for organ-sparing management.

Outcomes of Bosniak Classification Version 2019 Class IIF Cystic Renal Masses at Imaging Surveillance.

BACKGROUND. Bosniak classification system version 2019 (v2019) recommends that class IIF masses undergo follow-up imaging at 6 months, 12 months, and then annually for 5 years. The frequency and timing of upgrade on follow-up imaging are incompletely understood. OBJECTIVE. The purpose of this article is to describe the temporal evolution of Bosniak v2019 class IIF cystic renal masses, with attention to outcomes at 6-month follow-up, the time to class upgrade, and malignant histologic diagnoses. METHODS. This retrospective study included 219 patients (91 women, 128 men; median age, 72 years) with 246 localized class IIF masses from January 2005 to June 2022. Patients underwent both a baseline and at least one follow-up renal-mass protocol contrast-enhanced CT or MRI examination. Two radiologists evaluated masses at all follow-up time points to categorize masses as downgraded (class I or II), stable (localized class IIF), or upgraded (class III or IV, solid, or category T3a, N1, or M1 or higher disease); a third radiologist resolved discrepancies. Incidence rate of upgrade was determined. Histopathologic outcomes were assessed for resected masses. RESULTS. Median follow-up was 28.4 months (IQR, 13.7-59.4 months). At 6-month follow-up, five (2%) masses were downgraded, 241 (98%) were stable, and none were upgraded. On the basis of final follow-up, 14 (6%) masses were downgraded, 223 (91%) were stable, and nine (4%) were upgraded. All upgrade events entailed a class increase to III (n = 7) or IV (n = 2); no mass became solid or developed T3, N1, or M1 disease. Among the nine upgraded masses, median time to upgrade was 53.5 months (IQR, 23.2-63.7 months). Incidence rate of upgrade was 3.006 per 100,000 person-days (95% CI, 1.466-5.516). Ten masses were resected; histopathology was benign in six and malignant in four. Of the four malignant masses, one was upgraded to class III after 15 months of preoperative follow-up imaging, and three remained class IIF on preoperative follow-up imaging. No resected malignant mass developed postoperative recurrence. CONCLUSION. Bosniak v2019 class IIF masses are unlikely to represent aggressive malignancy; only 4% were upgraded over time and never on initial 6-month follow-up. CLINICAL IMPACT. The currently recommended initial 6-month follow-up imaging examination for class IIF masses is of questionable clinical utility.

External Validation of a Five-Tiered CT Algorithm for the Diagnosis of Clear Cell Renal Cell Carcinoma: A Retrospective Five-Reader Study.

BACKGROUND. In 2022, a five-tiered CT algorithm was proposed for predicting whether a small (cT1a) solid renal mass represents clear cell renal cell carcinoma (ccRCC). OBJECTIVE. The purpose of this external validation study was to evaluate the proposed CT algorithm for diagnosis of ccRCC among small solid renal masses. METHODS. This retrospective study included 93 patients (median age, 62 years; 42 women, 51 men) with 97 small solid renal masses that were seen on corticomedullary phase contrast-enhanced CT performed between January 2012 and July 2022 and subsequently underwent surgical resection. Five readers (three attending radiologists, two clinical fellows) independently evaluated masses for the mass-to-cortex corticomedullary attenuation ratio and heterogeneity score; these scores were used to derive the CT score by use of the previously proposed CT algorithm. The CT score's sensitivity, specificity, and PPV for ccRCC were calculated at threshold of 4 or greater, and the NPV for ccRCC was calculated at a threshold of 3 or greater (consistent with thresholds in studies of the MRI-based clear cell likelihood score and the CT algorithm's initial study). The CT score's sensitivity and specificity for papillary RCC were calculated at a threshold of 2 or less. Interreader agreement was assessed using the Gwet agreement coefficient (AC1). RESULTS. Overall, 61 of 97 masses (63%) were malignant and 43 of 97 (44%) were ccRCC. Across readers, CT score had sensitivity ranging from 47% to 95% (pooled sensitivity, 74% [95% CI, 68-80%]), specificity ranging from 19% to 83% (pooled specificity, 59% [95% CI, 52-67%]), PPV ranging from 48% to 76% (pooled PPV, 59% [95% CI, 49-71%]), and NPV ranging from 83% to 100% (pooled NPV, 90% [95% CI, 84-95%]), for ccRCC. A CT score of 2 or less had sensitivity ranging from 44% to 100% and specificity ranging from 77% to 98% for papillary RCC (representing nine of 97 masses). Interreader agreement was substantial for attenuation score (AC1 = 0.70), poor for heterogeneity score (AC1 = 0.17), fair for five-tiered CT score (AC1 = 0.32), and fair for dichotomous CT score at a threshold of 4 or greater (AC1 = 0.24 [95% CI, 0.14-0.33]). CONCLUSION. The five-tiered CT algorithm for evaluation of small solid renal masses was tested in an external sample and showed high NPV for ccRCC. CLINICAL IMPACT. The CT algorithm may be used for risk stratification and patient selection for active surveillance by identifying patients unlikely to have ccRCC.

Hepatocellular Adenoma Subtypes Based on 2017 Classification System: Exploratory Study of Gadoxetate Disodium-Enhanced MRI Features With Proposal of a Diagnostic Algorithm.

BACKGROUND. The classification of hepatocellular adenomas (HCAs) was updated in 2017 on the basis of genetic and molecular analysis. OBJECTIVE. The purpose of this article was to evaluate features on gadoxetate disodium-enhanced MRI of HCA subtypes on the basis of the 2017 classification and to propose a diagnostic algorithm for determining subtype using these features. METHODS. This retrospective study included 56 patients (49 women, seven men; mean age, 37 ± 13 [SD] years) with histologically confirmed HCA evaluated by gadoxetate disodium-enhanced MRI from January 2010 to January 2021. Subtypes were reclassified using 2017 criteria: hepatocyte nuclear factor-1α mutated HCA (HHCA), inflammatory HCA (IHCA), ß-catenin exon 3 activated HCA (ß-HCA), mixed inflammatory and ß-HCA (ß-IHCA), sonic hedgehog HCA (shHCA), and unclassified HCA (UHCA). Qualitative MRI features were assessed. Liver-to-lesion contrast enhancement ratios (LLCERs) were measured. Subtypes were compared, and a diagnostic algorithm was proposed. RESULTS. The analysis included 65 HCAs: 16 HHCAs, 31 IHCAs, six ß-HCA, four ß-IHCA, five shHCA, and three UHCAs. HHCAs showed homogeneous diffuse intralesional steatosis in 94%, whereas all other HCAs showed this finding in 0% (p < .001). IHCAs showed the "atoll" sign in 58%, whereas all other HCAs showed this finding in 12% (p < .001). IHCAs showed moderate T2 hyperintensity in 52%, whereas all other HCAs showed this finding in 12% (p < .001). The ß-HCAs and ß-IHCAs occurred in men in 63%, whereas all other HCAs occurred in men in 4% (p < .001). The ß-HCAs and ß-IHCAs had a mean size of 10.1 ± 6.8 cm, whereas all other HCAs had a mean size of 5.1 ± 2.9 cm (p = .03). The ß-HCAs and ß-IHCAs showed fluid components in 60%, whereas all other HCAs showed this finding in 5% (p < .001). Hepatobiliary phase iso- or hyperintensity was observed in 80% of ß-HCAs and ß-IHCAs versus 5% of all other HCAs (p < .001). Hepatobiliary phase LLCER was positive in nine HCAs (eight ß-HCAs and ß-IHCAs; one IHCA). The shHCA and UHCA did not show distinguishing features. The proposed diagnostic algorithm had accuracy of 98% for HHCAs, 83% for IHCAs, and 95% for ß-HCAs or ß-IHCAs. CONCLUSION. Findings on gadoxetate disodium-enhanced MRI, including hepatobiliary phase characteristics, were associated with HCA subtypes using the 2017 classification. CLINICAL IMPACT. The algorithm identified common HCA subtypes with high accuracy, including those with ß-catenin exon 3 mutations.

Hepatocellular Adenomas: Molecular Basis and Multimodality Imaging Update.

Hepatocellular adenomas (HCAs) are a family of liver tumors that are associated with variable prognoses. Since the initial description of these tumors, the classification of HCAs has expanded and now includes eight distinct genotypic subtypes based on molecular analysis findings. These genotypic subtypes have unique derangements in their cellular biologic makeup that determine their clinical course and may allow noninvasive identification of certain subtypes. Multiphasic MRI performed with hepatobiliary contrast agents remains the best method to noninvasively detect, characterize, and monitor HCAs. HCAs are generally hypointense during the hepatobiliary phase; the ß-catenin-mutated exon 3 subtype and up to a third of inflammatory HCAs are the exception to this characterization. It is important to understand the appearances of HCAs beyond their depictions at MRI, as these tumors are typically identified with other imaging modalities first. The two most feared related complications are bleeding and malignant transformation to hepatocellular carcinoma, although the risk of these complications depends on tumor size, subtype, and clinical factors. Elective surgical resection is recommended for HCAs that are persistently larger than 5 cm, adenomas of any size in men, and all ß-catenin-mutated exon 3 HCAs. Thermal ablation and transarterial embolization are potential alternatives to surgical resection. In the acute setting of a ruptured HCA, patients typically undergo transarterial embolization with or without delayed surgical resection. This update on HCAs includes a review of radiologic-pathologic correlations by subtype and imaging modality, related complications, and management recommendations. © RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Nyquist sampling theorem and Bosniak classification, version 2019: effect of thin axial sections on categorization and agreement.

OBJECTIVE: To determine if CT axial images reconstructed at current standard of care (SOC; 2.5-3 mm) or thin (≤ 1 mm) sections affect categorization and inter-rater agreement of cystic renal masses assessed with Bosniak classification, version 2019. METHODS: In this retrospective single-center study, 3 abdominal radiologists reviewed 131 consecutive cystic renal masses from 100 patients performed with CT renal mass protocol from 2015 to 2021. Images were reviewed in two sessions: first with SOC and then the addition of thin sections. Individual and overall categorizations are reported, latter of which is based on majority opinion with 3-way discrepancies resolved by a fourth reader. Major categorization changes were defined as differences between classes I-II, IIF, or III-IV. RESULTS: Thin sections led to a statistically significant major category change with class II for all readers individually (p = 0.004-0.041; McNemar test), upgrading 10-17% of class II masses, most commonly to class IIF followed by III. Modal reason for upgrades was due to identification of additional septa followed by larger measurement of enhancing features. Masses categorized as class I, III, or IV on SOC sections were unaffected, as were identification of protrusions. Inter-rater agreements using weighted Cohen's kappa were 0.679 for SOC and 0.691 for thin sections (both substantial). CONCLUSION: Thin axial sections upgraded up to one in six class II masses to IIF or III through identification of additional septa or larger feature. Other classes, including III-IV, were unaffected. Inter-rater agreements were substantial regardless of section thickness. KEY POINTS: • Thin axial sections (≤ 1 mm) compared to standard of care sections (2.5-3 mm) led to identification of additional septa but did not affect identification of protrusions. • Thin axial sections (≤ 1 mm) compared to standard of care sections (2.5-3 mm) can upgrade a small proportion of cystic renal masses from class II to IIF or III when applying Bosniak classification, version 2019. • Inter-rater agreements were substantial regardless of section thickness.

Outcomes of LI-RADS US-2 Subthreshold Observations Detected on Surveillance Ultrasound.

BACKGROUND. Ultrasound LI-RADS version 2017 recommends that patients with US-2 subthreshold observations undergo repeat surveillance ultrasound in 3-6 months and return to routine surveillance if the observation shows no growth for 2 years. However, outcomes of US-2 observations are unknown. OBJECTIVE. The purpose of this article was to determine imaging outcomes of US-2 observations detected on surveillance ultrasound examinations. METHODS. This retrospective study included 175 patients (median age, 59 years; 70 women, 105 men) at high risk for hepatocellular carcinoma (HCC) with US-2 observations (i.e., subcentimeter observations) on surveillance ultrasound. Observations were classified on follow-up ultrasound performed 2 or more years later as showing no correlate, stable (if remaining subcentimeter), or progressed (if measuring ≥ 10 mm, meeting US-3 criteria). Observations were classified on follow-up multiphasic CT or MRI (stratified as < 2-year vs ≥ 2-year follow-up) as showing no correlate or, if showing a correlate, using CT/MRI LI-RADS version 2018. RESULTS. A total of 111 patients had follow-up ultrasound after 2 or more years and 106 had follow-up CT or MRI (79 before 2 years, 27 after 2 years). On the basis of final follow-up examinations, 173 of 175 observations were stable on follow-up ultrasound 2 or more years later (n = 68); showed no correlate on follow-up ultrasound, CT, or MRI (n = 88); or were classified as LR-1 or LR-2 on CT or MRI (n = 17). The remaining 2 of 175 observations were LR-3 on CT or MRI. No observations progressed to US-3 on follow-up ultrasound or were classified as LR-4 or greater on CT or MRI. A correlate was observed in 25 of the 106 follow-up CT or MRI examinations (LR-1 or LR-2 in 23; LR-3 in two). Eight patients developed HCC at a median of 2.0 years after initial US-2 observation detection; all HCCs were in separate locations from the baseline observations and were preceded by a surveillance ultrasound that could not reidentify the baseline observation. In three patients who underwent liver transplant, the explant showed no dysplastic nodule or HCC. CONCLUSION. US-2 subthreshold observations are unlikely to progress or become HCC and commonly have no correlate on follow-up imaging. CLINICAL IMPACT. Because of the low progression rate of US-2 subthreshold observations, it is unclear if an extended period of intensive surveillance, as recommended by multiple professional societies, is warranted.

Growth Kinetics and Progression Rate of Bosniak Classification Version 2019 Class III and IV Cystic Renal Masses on Imaging Surveillance.

BACKGROUND. Active surveillance is increasingly used as first-line management for localized renal masses. Triggers for intervention primarily reflect growth kinetics, which have been poorly investigated for cystic masses defined by the Bosniak classification version 2019 (v2019). OBJECTIVE. The purpose of this study was to determine growth kinetics and incidence rates of progression of class III and IV cystic renal masses, as defined by the Bosniak classification v2019. METHODS. This retrospective study included 105 patients (68 men, 37 women; median age, 67 years) with 112 Bosniak v2019 class III or IV cystic renal masses on baseline renal mass protocol CT or MRI examinations performed from January 2005 to September 2021. Mass dimensions were measured. Progression was defined as any of the following: linear growth rate (LGR) of 5 mm/y or greater (representing the clinical guideline threshold for intervention), volume doubling time less than 1 year, T category increase, or N1 or M1 disease. Class III and IV masses were compared. Time to progression was estimated using Kaplan-Meier curve analysis. RESULTS. At baseline, 58 masses were class III and 54 were class IV. Median follow-up was 403 days. Median LGR for class III masses was 0.0 mm/y (interquartile range [IQR], -1.3 to 1.8 mm/y) and for class IV masses was 2.3 mm/y (IQR, 0.0-5.7 mm/y) (p < .001). LGR was at least 5 mm/y in four (7%) class III masses and 15 (28%) class IV masses (p = .005). Two patients, both with class IV masses, developed distant metastases. Incidence rate of progression for class III masses was 11.0 (95% CI, 4.5-22.8) and for class IV masses 73.6 (95% CI, 47.8-108.7) per 100,000 person-days of follow-up. Median time to progression was undefined for class III masses given the small number of progression events and 710 days for class IV masses. Hazard ratio of progression for class IV relative to class III masses was 5.1 (95% CI, 2.5-10.8; p < .001). CONCLUSION. During active surveillance of cystic masses evaluated using the Bosniak classification v2019, class IV masses grew faster and were more likely to progress than class III masses. CLINICAL IMPACT. In comparison with current active surveillance guidelines that treat class III and IV masses similarly, future iterations may incorporate relatively more intensive surveillance for class IV masses.

CT Angiography of Venoarterial Extracorporeal Membrane Oxygenation.

Imaging plays a central role in the workup of thromboembolic events and bleeding complications in patients treated with venoarterial extracorporeal membrane oxygenation (ECMO) (VA-ECMO), and radiologists should be familiar with the expected hemodynamic changes and flow-related artifacts associated with the VA-ECMO system. VA-ECMO is a form of temporary mechanical circulatory support for critically ill patients with acute, refractory cardiac or cardiopulmonary failure. As the use of VA-ECMO continues to increase, it is important to be aware of associated hemodynamic changes and challenges at imaging. Patients treated with VA-ECMO are at high risk for thromboembolic events and bleeding complications and, thus, often require evaluation with CT angiography (CTA). VA-ECMO can be implemented by using central or peripheral cannulation. The peripheral femorofemoral VA-ECMO circuit in particular alters the sequence and direction of contrast medium enhancement substantially, resulting in flow-related artifacts that can mimic or obscure disease at CTA. Nonopacification can be mistaken for spurious thrombus or simulate complete vascular occlusion, while mixing artifacts can mimic dissections. Misinterpretation of flow-related CTA artifacts can lead to inappropriate surgical or medical intervention. A methodical and multiphasic approach should be taken to CTA imaging strategies and interpretation for patients treated with VA-ECMO. There is no universal CTA protocol for patients on VA-ECMO. Each protocol must be designed for the study indication, with consideration of the configuration of the ECMO cannulas, contrast material injection site, region of interest, native cardiac output, and ECMO flow rate. The authors provide examples of common and unusual VA-ECMO-related artifacts, with a focus on strategies for optimizing CTA image acquisition. Online supplemental material is available for this article. ©RSNA, 2021.

Thoracic Endovascular Aortic Repair for Chronic Type B Aortic Dissection: Pre- and Postprocedural Imaging.

Aortic dissection is a chronic disease that requires lifelong clinical and imaging surveillance, long after the acute event. Imaging has an important role in prognosis, timing of repair, device sizing, and monitoring for complications, especially in the endovascular therapy era. Important anatomic features at preprocedural imaging include the location of the primary intimal tear and aortic zonal and branch vessel involvement, which influence the treatment strategy. Challenges of repair in the chronic phase include a small true lumen in conjunction with a stiff intimal flap, complex anatomy, and retrograde perfusion from distal reentry tears. The role of thoracic endovascular aortic repair (TEVAR) remains controversial for treatment of chronic aortic dissection. Standard TEVAR is aimed at excluding the primary intimal tear to decrease false lumen perfusion, induce false lumen thrombosis, promote aortic remodeling, and prevent aortic growth. In addition to covering the primary intimal tear with an endograft, several adjunctive techniques have been developed to mitigate retrograde false lumen perfusion. These techniques are broadly categorized into false lumen obliteration and landing zone optimization strategies, such as the provisional extension to induce complete attachment (PETTICOAT), false lumen embolization, cheese-wire fenestration, and knickerbocker techniques. Familiarity with these techniques is important to recognize expected changes and complications at postintervention imaging. The authors detail imaging options, provide examples of simple and complex endovascular repairs of aortic dissections, and highlight complications that can be associated with various techniques. Online supplemental material is available for this article. ©RSNA, 2022.

Reproducibility and repeatability of a semi-automated pipeline to quantify trapeziometacarpal joint angles using dynamic computed tomography.

BACKGROUND: The trapeziometacarpal (TMC) joint is a mechanically complex joint and is commonly affected by musculoskeletal diseases such as osteoarthritis. Quantifying in vivo TMC joint biomechanics, such as joint angles, with traditional reflective marker-based methods can be difficult due to the joint's location in the hand. Dynamic computed tomography (CT) can facilitate the quantification of TMC joint motion by continuously capturing three-dimensional volumes over time. However, post-processing of dynamic CT datasets can be time intensive and automated methods are needed to reduce processing times to allow for application to larger clinical studies. The purpose of this work is to introduce a fast, semi-automated pipeline to quantify joint angles from dynamic CT scans of the TMC joint and evaluate the associated error in joint angle and translation computation by means of a reproducibility and repeatability study. METHODS: Ten cadaveric hands were scanned with dynamic CT using a passive motion device to move thumbs in a radial abduction-adduction motion. Static CT scans and high-resolution peripheral quantitative CT scans were also acquired to generate high-resolution bone meshes. Abduction-adduction, flexion-extension, and axial rotation angles were computed using a joint coordinate system. Reproducibility and repeatability were assessed using intraclass correlation coefficients, Bland-Altman analysis, and root mean square errors. Target registration errors were computed to evaluate errors associated with image registration. RESULTS: We found good repeatability for flexion-extension, abduction-adduction, and axial rotation angles. Reproducibility was moderate for all three angles. Joint translations exhibited greater repeatability than reproducibility. Specimens with greater joint degeneration had lower repeatability and reproducibility. We found that the difference in resulting joint angles and translations were likely due to differences in segment coordinate system definition between multiple raters, rather than due to registration errors. CONCLUSIONS: The proposed semi-automatic processing pipeline was fast, repeatable, and moderately reproducible when quantifying TMC joint angles and translations. This work provides a range of errors for TMC joint angles from dynamic CT scans using manually selected anatomical landmarks.