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BACKGROUND: Solid small renal masses (SRMs, ≤4 cm) represent benign and malignant tumors. Among SRMs, clear cell renal cell carcinoma (ccRCC) is frequently aggressive. Compared to invasive percutaneous biopsies, a proposed clear cell likelihood score (ccLS) aims to diagnose ccRCC non-invasively using multiparametric MRI (mpMRI), but lacks external validation. PURPOSE: To evaluate the performance of and interobserver agreement for ccLS to diagnose ccRCC among solid SRMs. MATERIALS AND METHODS: This retrospective, multicenter, cross-sectional study included patients with consecutive solid (≥25% approximate volume enhancement) SRMs undergoing mpMRI between December 2012 and December 2019 at five academic medical centers with histological confirmation of diagnosis. Masses with macroscopic fat were excluded. After a 1.5-hour training session, two abdominal radiologists per center independently rendered a ccLS for 50 masses. The diagnostic performance for ccRCC was calculated using random-effects logistic regression modeling. The distribution of ccRCC by ccLS was tabulated. Interobserver agreement for ccLS was evaluated with Fleiss Kappa. RESULTS: 241 patients (mean±SD age, 60 ± 13 years, 174 men) with 250 solid SRMs were evaluated. The mean ±SD size was 25±8 mm (range 10–39 mm). 48% (119/250) of SRMs were ccRCC. The sensitivity, specificity, and positive predictive value for the diagnosis of ccRCC (95% CI) when ccLS≥4 were 75% (68%, 81%), 78% (72%, 84%), and 76% (69%, 81%), respectively. The negative predictive value of ccLS≤2 was 88% (81%, 93%). The percentages of ccRCC according to the ccLS were 6% (range, 0%–18%), 38% (range, 0%–100%), 32% (range, 18%–53%), 72% (range, 20%–100%), and 81% (range, 50%–100%) for ccLS 1–5, respectively. The mean interobserver agreement was moderate (Kappa=0.58 [95% CI: 0.42, 0.75]). CONCLUSION: The clear cell likelihood score applied to multiparametric MRI had moderate interobserver agreement and differentiated clear cell renal cell carcinoma from other solid renal masses with a negative predictive value of 88%. SUMMARY: Clear cell likelihood scores provide a framework for standardized multiparametric MRI assessment of solid small renal masses with moderate diagnostic accuracy for clear cell renal cell carcinoma.

Purpose The aim was to quantify inter- and intra-observer variability in manually delineated lesion contours and the resulting impact on radionuclide therapy dosimetry. Methods Ten patients with hepatocellular carcinoma lesions treated with 90Y radioembolization (RE) and imaged with post-therapy 90Y PET/CT were selected for retrospective analysis. Three radiologists contoured 20 lesions manually on baseline multiphase contrast-enhanced MRIs and two of the radiologists re-contoured at two additional sessions. Contours were transferred to co-registered PET/CT-based 90Y dose-maps. Volume-dependent recovery-coefficients (RCs) were applied for partial volume correction when reporting mean absorbed dose. To understand how uncertainty varies with tumor size, we fit power models regressing relative uncertainty in volume and in mean absorbed dose on contour volume. Finally, we determined effects of uncertainty on tumor control probability (TCP), as calculated using logistic models developed in a previous report for lesions treated with RE. Results The average lesion volume ranged from 1.8 mL to 194.5 mL and the mean absorbed dose ranged from 23.4 to 1,629.0 Gy. The mean inter-observer Dice coefficient for lesion contours was significantly less than the mean intra-observer Dice coefficient (0.79 vs. 0.85, p < 0.001). Uncertainty in volume, as measured by the Coefficient of Variation (CV) ranged from 4.2% to 34.7% with a mean of 17.2%. For lesions > 8 mL, the CV in mean absorbed dose had an average value of 7.2% (range 1.5% to 12.6%) while for smaller lesions it was 21.7% (range 8.4 to 55.2%). The fitted uncertainty curves as a function of volume, v (in mL), were: %CV (volume) = 23.0* v-0.17 and %CV (mean dose) = 32.4* v-0.44. With this model for uncertainty, the mean change in TCP was 16.2% (maximum 48.5%). Conclusion Though we find relatively high inter- and intra-observer reliability overall, uncertainty in tumor contouring propagates into non-negligible uncertainty in dose metrics and outcome prediction for individual cases that should be considered in dosimetry-guided treatment.

BACKGROUND: The Bosniak classification system for cystic renal masses was updated in 2019 in part to improve agreement compared with the 2005 version. PURPOSE: To compare and investigate interrater agreement of Bosniak version 2019 and Bosniak version 2005 at CT and MRI. MATERIALS AND METHODS: In this retrospective single-center study, a blinded eight-reader assessment was performed in which 195 renal masses prospectively considered Bosniak IIF–IV (95 at CT, 100 at MRI, from 2006 to 2019 with version 2005) were re-evaluated with Bosniak versions 2019 and 2005. Radiologists (four faculty members, four residents) who were blinded to the initial clinical reading and histopathologic findings assessed all feature components and reported the overall Bosniak class for each system independently. Agreement was assessed with Gwet agreement coefficients. Uni- and multivariable linear regression models were developed to identify predictors of dispersion in the final Bosniak class assignment that could inform system refinement. RESULTS: A total of 185 patients were included (mean age, 63 years ± 13 [standard deviation]; 118 men). Overall interrater agreement was similar between Bosniak version 2019 and version 2005 (Gwet agreement coefficient: 0.51 [95% CI: 0.45, 0.57] vs 0.46 [95% CI: 0.42, 0.51]). This was true for experts (0.54 vs 0.49) and novices (0.50 vs 0.47) and at CT (0.56 vs 0.51) and MRI (0.52 vs 0.43). Nine percent of masses prospectively considered cystic using Bosniak version 2005 criteria were considered solid using version 2019 criteria. In general, masses were more commonly classified in lower categories when radiologists used Bosniak version 2019 criteria compared with version 2005 criteria. The sole predictor of dispersion in Bosniak version 2019 class assignment was dispersion in septa or wall quality (ie, smooth vs irregular thickening vs nodule; 72% [MRI] and 60% [CT] overall model variance explained; multivariable P < .001). CONCLUSION: Overall interrater agreement was similar between Bosniak version 2019 and version 2005; disagreements in septa or wall quality were common and strongly predictive of variation in Bosniak class assignment. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Eberhardt in this issue.

Rationale and Objectives To evaluate whether a computed tomography (CT)-based computerized decision-support system for muscle-invasive bladder cancer treatment response assessment (CDSS-T) can improve identification of patients who have responded completely to neoadjuvant chemotherapy. Materials and Methods Following Institutional Review Board approval, pre-chemotherapy and post-chemotherapy CT scans of 123 subjects with 157 muscle-invasive bladder cancer foci were collected retrospectively. CT data were analyzed with a CDSS-T that uses a combination of deep-learning convolutional neural network and radiomic features to distinguish muscle-invasive bladder cancers that have fully responded to neoadjuvant treatment from those that have not. Leave-one-case-out cross-validation was used to minimize overfitting. Five attending abdominal radiologists, four diagnostic radiology residents, two attending oncologists, and one attending urologist estimated the likelihood of pathologic T0 disease (complete response) by viewing paired pre/post-treatment CT scans placed side-by-side on an internally-developed graphical user interface. The observers provided an estimate without use of CDSS-T and then were permitted to revise their estimate after a CDSS-T-derived likelihood score was displayed. Observer estimates were analyzed with multi-reader, multi-case receiver operating characteristic methodology. The area under the curve (AUC) and the statistical significance of the difference were estimated. Results The mean AUCs for assessment of pathologic T0 disease were 0.80 for CDSS-T alone, 0.74 for physicians not using CDSS-T, and 0.77 for physicians using CDSS-T. The increase in the physicians' performance was statistically significant (P Conclusion CDSS-T improves physician performance for identifying complete response of muscle-invasive bladder cancer to neoadjuvant chemotherapy.

Purpose The purpose of this study was to evaluate the frequency, indications, and findings of abdominal CTs ordered in the initial evaluation of patients who had a positive COVID-19 test performed in our institution. Methods Retrospective chart review was performed on all patients who had a positive test for COVID-19 performed at a single quaternary care center from 1/20/2020 through 5/8/2020. In a subset of patients undergoing abdominal CT as part of the initial evaluation, the demographics, suspected COVID-19 status at the time of scan, presenting complaints, and abdominal CT findings were recorded. Cardiothoracic radiologists reviewed and scored the visualized lung bases for the likelihood of COVID-19. Results Only 43 (4.1%) of 1057 COVID-19 patients presented with abdominal complaints sufficient to warrant an abdominal CT. Of these 43 patients, the vast majority (39, 91%) were known or suspected to have COVID-19 at the time of the scan. Most (27/43, 63%) scans showed no acute abdominal abnormality, and those that were positive did not share a discernable pattern of abnormalities. Lung base abnormalities were common, and there was moderate inter-reviewer reliability. Conclusion A minority of COVID-19 patients present with abdominal complaints sufficient to warrant a dedicated CT of the abdomen, and most of these studies will be negative or have abdominal findings not associated with COVID-19. Appropriate lung base findings are a more consistent indication of COVID-19 infection than abdominal findings.

We evaluated the intraobserver variability of physicians aided by a computerized decision-support system for treatment response assessment (CDSS-T) to identify patients who show complete response to neoadjuvant chemotherapy for bladder cancer, and the effects of the intraobserver variability on physicians' assessment accuracy. A CDSS-T tool was developed that uses a combination of deep learning neural network and radiomic features from computed tomography (CT) scans to detect bladder cancers that have fully responded to neoadjuvant treatment. Pre- and postchemotherapy CT scans of 157 bladder cancers from 123 patients were collected. In a multireader, multicase observer study, physician-observers estimated the likelihood of pathologic T0 disease by viewing paired pre/posttreatment CT scans placed side by side on an in-house-developed graphical user interface. Five abdominal radiologists, 4 diagnostic radiology residents, 2 oncologists, and 1 urologist participated as observers. They first provided an estimate without CDSS-T and then with CDSS-T. A subset of cases was evaluated twice to study the intraobserver variability and its effects on observer consistency. The mean areas under the curves for assessment of pathologic T0 disease were 0.85 for CDSS-T alone, 0.76 for physicians without CDSS-T and improved to 0.80 for physicians with CDSS-T (P = .001) in the original evaluation, and 0.78 for physicians without CDSS-T and improved to 0.81 for physicians with CDSS-T (P = .010) in the repeated evaluation. The intraobserver variability was significantly reduced with CDSS-T (P &lt, 0001). The CDSS-T can significantly reduce physicians' variability and improve their accuracy for identifying complete response of muscle-invasive bladder cancer to neoadjuvant chemotherapy.

Lymph node involvement in bladder cancer is common and has prognostic implications. Early and accurate identification of metastatic lymph nodes is, therefore, important in ensuring appropriate patient triage and management. The purpose of this review is to provide a pictorial and educational overview of the staging and imaging appearance of metastatic lymph nodes in bladder cancer. Additionally, a secondary aim of this manuscript is to provide a review of the diagnostic accuracy of common imaging modalities available for detecting metastatic lymph nodes in affected patients.

Crohn disease is a chronic inflammatory condition that can lead to intestinal strictures. The presence of fibrosis within strictures alters optimal management but is not reliably detected by current imaging methods.To correlate the MRI features of surgically resected small-bowel strictures in pediatric Crohn disease with histological inflammation and fibrosis scoring.We included children with Crohn disease who had symptomatic small-bowel strictures requiring surgical resection and had preoperative MR enterography (MRE) within 3 months of surgery (n = 20). Two blinded radiologists reviewed MRE examinations to document stricture-related findings. A pediatric pathologist scored stricture histological specimens for fibrosis (0-4) and inflammation (0-4). MRE findings were correlated with histological data using Spearman correlation (ρ) and exact logistic regression analysis.There was significant positive correlation between histological bowel wall fibrosis and inflammation in resected strictures (ρ = 0.55; P = 0.01). Confluent transmural histological fibrosis was associated with pre-stricture upstream small-bowel dilatation3 cm at univariate (odds ratio [OR] = 51.7; 95% confidence interval [CI]: 7.6- 999.9; P = 0.0002) and multivariate (OR = 43.4; 95% CI: 6.1- 999.9; P = 0.0006, adjusted for age) analysis. The degree of bowel wall T2-weighted signal intensity failed to correlate with histological bowel wall fibrosis or inflammation (P-values0.05). There were significant negative correlations between histological fibrosis score and patient age at resection (ρ = -0.48, P = 0.03), and time from diagnosis to surgery (ρ = -0.73, P = 0.0002).Histological fibrosis and inflammation co-exist in symptomatic pediatric Crohn disease small-bowel strictures and are positively correlated. Pre-stenotic upstream small-bowel dilatation greater than 3 cm is significantly associated with confluent transmural fibrosis.

Acute renal conditions account for a notable volume of Emergency Department visits and often lead to imaging. Urolithiasis is the most commonly encountered etiology but a wide range of conditions including infection, inflammation, and hemorrhage can also cause acute pain. Ultrasound and computed tomography (CT) are the most commonly utilized imaging modalities for the kidneys while the role of dual-energy CT is expanding as a problem-solving tool. Management of acute renal conditions ranges from emergent intervention to medical management and may be determined by the imaging findings. Therefore, accurate and timely diagnoses are critical to expedite appropriate clinical management.