CT-based Bosniak classification of cystic renal lesions: is version 2019 an improvement on version 2005?

OBJECTIVE: To compare the diagnostic performance and inter-reader agreement of the CT-based v2019 versus v2005 Bosniak classification systems for risk stratification of cystic renal lesions (CRL). METHODS: This retrospective study included adult patients with CRL identified on CT scan between 2005 and 2018. The reference standard was histopathology or a minimum 4-year imaging follow-up. The studies were reviewed independently by five readers (three senior, two junior), blinded to pathology results and imaging follow-up, who assigned Bosniak categories based on the 2005 and 2019 versions. Diagnostic performance of v2005 and v2019 Bosniak classifications for distinguishing benign from malignant lesions was calculated by dichotomizing CRL into the potential for ablative therapy (III-IV) or conservative management (I-IIF). Inter-reader agreement was calculated using Light's Kappa. RESULTS: One hundred thirty-nine patients with 149 CRL (33 malignant) were included. v2005 and v2019 Bosniak classifications achieved similar diagnostic performance with a sensitivity of 91% vs 91% and a specificity of 89% vs 88%, respectively. Inter-reader agreement for overall Bosniak category assignment was substantial for v2005 (κ = 0.78) and v2019 (κ = 0.75) between senior readers but decreased for v2019 when the Bosniak classification was dichotomized to conservative management (I-IIF) or ablative therapy (III-IV) (0.80 vs 0.71, respectively). For v2019, wall thickness was the morphological feature with the poorest inter-reader agreement (κ = 0.43 and 0.18 for senior and junior readers, respectively). CONCLUSION: No significant improvement in diagnostic performance and inter-reader agreement was shown between v2005 and v2019. The observed decrease in inter-reader agreement in v2019 when dichotomized according to management strategy may reflect the more stringent morphological criteria. KEY POINTS: • Versions 2005 and 2019 Bosniak classifications achieved similar diagnostic performance, but the specificity of higher risk categories (III and IV) was not increased while one malignant lesion was downgraded to v2019 Bosniak category II (i.e., not subjected to further follow-up). • Inter-reader agreement was similar between v2005 and v2019 but moderately decreased for v2019 when the Bosniak classification was dichotomized according to the potential need for ablative therapies (I-II-IIF vs III-IV).

Malignancy risk stratification of cystic renal lesions based on a contrast-enhanced CT-based machine learning model and a clinical decision algorithm.

OBJECTIVE: To distinguish benign from malignant cystic renal lesions (CRL) using a contrast-enhanced CT-based radiomics model and a clinical decision algorithm. METHODS: This dual-center retrospective study included patients over 18 years old with CRL between 2005 and 2018. The reference standard was histopathology or 4-year imaging follow-up. Training and testing datasets were acquired from two institutions. Quantitative 3D radiomics analyses were performed on nephrographic phase CT images. Ten-fold cross-validated LASSO regression was applied to the training dataset to identify the most discriminative features. A logistic regression model was trained to classify malignancy and tested on the independent dataset. Reported metrics included areas under the receiver operating characteristic curves (AUC) and balanced accuracy. Decision curve analysis for stratifying patients for surgery was performed in the testing dataset. A decision algorithm was built by combining consensus radiological readings of Bosniak categories and radiomics-based risks. RESULTS: A total of 149 CRL (139 patients; 65 years [56-72]) were included in the training dataset-35 Bosniak(B)-IIF (8.6% malignancy), 23 B-III (43.5%), and 23 B-IV (87.0%)-and 50 CRL (46 patients; 61 years [51-68]) in the testing dataset-12 B-IIF (8.3%), 10 B-III (60.0%), and 9 B-IV (100%). The machine learning model achieved high diagnostic performance in predicting malignancy in the testing dataset (AUC = 0.96; balanced accuracy = 94%). There was a net benefit across threshold probabilities in using the clinical decision algorithm over management guidelines based on Bosniak categories. CONCLUSION: CT-based radiomics modeling accurately distinguished benign from malignant CRL, outperforming the Bosniak classification. The decision algorithm best stratified lesions for surgery and active surveillance. KEY POINTS: • The radiomics model achieved excellent diagnostic performance in identifying malignant cystic renal lesions in an independent testing dataset (AUC = 0.96). • The machine learning-enhanced decision algorithm outperformed the management guidelines based on the Bosniak classification for stratifying patients to surgical ablation or active surveillance.

Ultra-high-frequency ultrasound of superficial and musculoskeletal structures in the pediatric population.

Because of its relatively low cost, lack of ionizing radiation and great versatility, US is considered the imaging modality of choice to evaluate a large variety of pediatric conditions. Imaging of superficial structures and small anatomical parts can be at times limited with standard US. Recent advances in technology yielded ultra-high-frequency US systems that are capable of scanning with frequencies as high as 70 MHz and resolutions of 30 µm. This technology, approved by the United States Food and Drug Administration, has not been widely used in the clinical setting. It has the potential to become a powerful diagnostic tool in clinical practice, especially in the evaluation of infants, given their inherent body habitus. Our main objective is to discuss the use of ultra-high-frequency US at a tertiary care center. This pictorial essay presents a gamut of pediatric pathologies pertaining to imaging of the soft tissues and the superficial and musculoskeletal structures. Our aim in this pictorial essay is to highlight and illustrate the role of ultra-high-frequency US in improving the depiction of common and less common pathologies. We think it also helps to gain a new understanding of the normal anatomy in the pediatric population and to display specific features not shown by standard US and, in certain cases, ones that lead to a change in diagnosis.

Inter-reader agreement of the Society of Abdominal Radiology-American Gastroenterological Association (SAR-AGA) consensus reporting for key phenotypes at MR enterography in adults with Crohn disease: impact of radiologist experience.

PURPOSE: To assess inter-reader agreement of key features from the SAR-AGA recommendations for the interpretation and reporting of MRE in adult patients with CD, focusing on the impact of radiologist experience on inter-reader agreement of CD phenotypes. METHODS: Two experienced and two less-experienced radiologists retrospectively evaluated 99 MRE in CD patients (50 initial MRE, 49 follow-up MRE) performed from 1/1/2019 to 3/20/2020 for the presence of active bowel inflammation (stomach, proximal small bowel, ileum, colon), stricture, probable stricture, penetrating disease, and perianal disease. The MRE protocol did not include dedicated perianal sequences. Inter-rater agreement was determined for each imaging feature using prevalence-adjusted bias-adjusted kappa and compared by experience level. RESULTS: All readers had almost-perfect inter-reader agreement (κ > 0.90) for penetrating disease, abscess, and perianal abscess in all 99 CD patients. All readers had strong inter-reader agreement (κ: 0.80-0.90) in 99 CD patients for active ileum inflammation, proximal small bowel inflammation, and stricture. Less-experienced readers had significantly lower inter-reader agreement for active ileum inflammation on initial than follow-up MRE (κ 0.68 versus 0.96, p = 0.018) and for strictures on follow-up than initial MRE (κ 0.76 versus 1.0, p = 0.027). Experienced readers had significantly lower agreement for perianal fistula on follow-up than initial MRE (κ: 0.55 versus 0.92, p = 0.008). CONCLUSION: There was strong to almost-perfect inter-reader agreement for key CD phenotypes described in the SAR-AGA consensus recommendations including active ileum and proximal small bowel inflammation, stricture, penetrating disease, abscess, and perianal abscess. Areas of lower inter-reader agreement could be targeted for future education efforts to further standardize CD MRE reporting. Dedicated perianal sequences should be included on follow-up MRE.

18F-fluorocholine positron emission tomography-computed tomography (18F-FCH PET/CT) for staging of high-risk prostate cancer patients.

INTRODUCTION: We sought to evaluate the diagnostic performance of 18F-fluorocholine positron emission tomography-computed tomography (18F-FCH PET/CT) for initial staging of patients with high-risk prostate cancer. Secondary objectives were to compare the value of 18F-FCH PET/CT to conventional imaging modalities and to evaluate its clinical impact. METHODS: We conducted a retrospective study of 76 patients who underwent 18F-FCH PET/CT for initial staging of high-risk prostate cancer. Using pre-established validation criteria, sensitivity and specificity were determined for metastatic disease. Results were compared to findings on magnetic resonance imaging (MRI), computed tomography (CT), and bone scan (BS) when available. RESULTS: Twenty-two (29%) PET/CT scans were positive, 49 (64%) negative, and five (7%) equivocal for nodal or metastatic disease. Of the positive scans, 17 showed regional lymph node involvement, 12 distant nodes, five bone metastases, and three lung metastases. Overall per-patient sensitivity, specificity, positive and negative predictive values for metastatic disease were 65%, 100%, 100%, and 78%, respectively. Sensitivity, specificity, and positive and negative predictive values were 64%, 100%, 100%, and 80%, respectively, for nodal involvement and 86%, 100%, 100%, and 98%, respectively, for bone and other metastases. Conventional imaging was negative for the lesion(s) found on PET/CT in five patients. PET/CT changed the clinical management in nine patients (12%). CONCLUSIONS: Although 18F-FCH PET/CT offers some benefits over conventional imaging and demonstrates a high specificity, it remains limited by its sensitivity in the context of high-risk prostate cancer staging. PET with novel urea-based small molecule prostate-specific membrane antigen (PSMA) inhibitors may overcome some of these limitations. However, the interpretation of the study result is limited by the lack of available histological gold standard, the inclusion of several patients who received androgen-deprivation therapy (ADT) prior to PET/CT, our retrospective design, and a relatively small sample size.

Initial single-centre Canadian experience with 18F-fluoromethylcholine positron emission tomography-computed tomography (18F-FCH PET/CT) for biochemical recurrence in prostate cancer patients initially treated with curative intent.

INTRODUCTION: We sought to determine predictive factors (patient and prostate-specific antigen [PSA] characteristics) for 18F-fluoromethylcholine positron emission tomography-computed tomography (18F-FCH PET/CT) positivity in the context of biochemical recurrence after local treatment of prostate cancer (PCa) with curative intent. METHODS: This is a retrospective study including 60 18F-FCH PET/CT scans of patients with biochemical recurrence after initial radical prostatectomy (RP), external beam radiation therapy (EBRT), or focal high-intensity focused ultrasound (HIFU) with curative intent. The results were compared to findings on magnetic resonance imaging (MRI), computed tomography (CT), bone scan (BS), and histological analysis when available. Univariate analysis was performed to correlate results with patient characteristics. RESULTS: Thirty-eight (63.3%) scans were positive, 17 (28.3%) negative, and 5 (8.3%) equivocal. Of the positive scans, 16 demonstrated local recurrence, 12 regional/distant lymph nodes, five bone metastasis, and five local and distant recurrences. Among the 22 PET/CTs showing metastasis, conventional imaging was performed in 16 patients (72.7%). Of these, it demonstrated the lesion(s) found on PET/CT in eight patients (50.0%), was negative in seven (43.8%), and equivocal in one (6.3%). The trigger PSA (p=0.04), prostate-specific antigen velocity (PSAV) (p=0.03), and prostate-specific antigen doubling time (PSADT) (p=0.046) were significantly different when comparing positive and negative scans. Patients with positive scans were more likely to have received EBRT initially (odds ratio [OR] 11.0, 95% confidence interval [CI] 2.2-55.3). A trigger PSA of 2.6 ng/mL had a sensitivity of 84% and specificity of 65% for a positive scan. PET/CT changed the clinical management plan in 17 patients (28.3%). CONCLUSIONS: 18F-FCH PET/CT demonstrates a high detection rate for local and distant recurrences after localized PCa treatment. A trigger PSA above 2.6 ng/mL seems optimal for appropriate patient selection.