Characterization of renal masses with MRI-based radiomics: assessment of inter-package and inter-observer reproducibility in a prospective pilot study.

OBJECTIVES: To evaluate radiomics features' reproducibility using inter-package/inter-observer measurement analysis in renal masses (RMs) based on MRI and to employ machine learning (ML) models for RM characterization. METHODS: 32 Patients (23M/9F; age 61.8 ± 10.6 years) with RMs (25 renal cell carcinomas (RCC)/7 benign masses; mean size, 3.43 ± 1.73 cm) undergoing resection were prospectively recruited. All patients underwent 1.5 T MRI with T2-weighted (T2-WI), diffusion-weighted (DWI)/apparent diffusion coefficient (ADC), and pre-/post-contrast-enhanced T1-weighted imaging (T1-WI). RMs were manually segmented using volume of interest (VOI) on T2-WI, DWI/ADC, and T1-WI pre-/post-contrast imaging (1-min, 3-min post-injection) by two independent observers using two radiomics software packages for inter-package and inter-observer assessments of shape/histogram/texture features common to both packages (104 features; n = 26 patients). Intra-class correlation coefficients (ICCs) were calculated to assess inter-observer and inter-package reproducibility of radiomics measurements [good (ICC ≥ 0.8)/moderate (ICC = 0.5-0.8)/poor (ICC < 0.5)]. ML models were employed using reproducible features (between observers and packages, ICC > 0.8) to distinguish RCC from benign RM. RESULTS: Inter-package comparisons demonstrated that radiomics features from T1-WI-post-contrast had the highest proportion of good/moderate ICCs (54.8-58.6% for T1-WI-1 min), while most features extracted from T2-WI, T1-WI-pre-contrast, and ADC exhibited poor ICCs. Inter-observer comparisons found that radiomics measurements from T1-WI pre/post-contrast and T2-WI had the greatest proportion of features with good/moderate ICCs (95.3-99.1% T1-WI-post-contrast 1-min), while ADC measurements yielded mostly poor ICCs. ML models generated an AUC of 0.71 [95% confidence interval = 0.67-0.75] for diagnosis of RCC vs. benign RM. CONCLUSION: Radiomics features extracted from T1-WI-post-contrast demonstrated greater inter-package and inter-observer reproducibility compared to ADC, with fair accuracy for distinguishing RCC from benign RM. CLINICAL RELEVANCE: Knowledge of reproducibility of MRI radiomics features obtained on renal masses will aid in future study design and may enhance the diagnostic utility of radiomics models for renal mass characterization.

Prediction of locally advanced rectal cancer response to neoadjuvant chemoradiation therapy using volumetric multiparametric MRI-based radiomics.

PURPOSE: To assess the role of pretreatment multiparametric (mp)MRI-based radiomic features in predicting pathologic complete response (pCR) of locally advanced rectal cancer (LARC) to neoadjuvant chemoradiation therapy (nCRT). METHODS: This was a retrospective dual-center study including 98 patients (M/F 77/21, mean age 60 years) with LARC who underwent pretreatment mpMRI followed by nCRT and total mesorectal excision or watch and wait. Fifty-eight patients from institution 1 constituted the training set and 40 from institution 2 the validation set. Manual segmentation using volumes of interest was performed on T1WI pre-/post-contrast, T2WI and diffusion-weighted imaging (DWI) sequences. Demographic information and serum carcinoembryonic antigen (CEA) levels were collected. Shape, 1st and 2nd order radiomic features were extracted and entered in models based on principal component analysis used to predict pCR. The best model was obtained using a k-fold cross-validation method on the training set, and AUC, sensitivity and specificity for prediction of pCR were calculated on the validation set. RESULTS: Stage distribution was T3 (n = 79) or T4 (n = 19). Overall, 16 (16.3%) patients achieved pCR. Demographics, MRI TNM stage, and CEA were not predictive of pCR (p range 0.59-0.96), while several radiomic models achieved high diagnostic performance for prediction of pCR (in the validation set), with AUCs ranging from 0.7 to 0.9, with the best model based on high b-value DWI demonstrating AUC of 0.9 [95% confidence intervals: 0.67, 1], sensitivity of 100% [100%, 100%], and specificity of 81% [66%, 96%]. CONCLUSION: Radiomic models obtained from pre-treatment MRI show good to excellent performance for the prediction of pCR in patients with LARC, superior to clinical parameters and CEA. A larger study is needed for confirmation of these results.

Eliciting Patient Preferences for Hepatocellular Carcinoma Screening: A Choice-Based Conjoint Analysis.

BACKGROUND: Abbreviated MRI (AMRI), proposed as an alternative imaging modality for hepatocellular carcinoma screening, provides higher sensitivity than ultrasound. It is, however, unknown how patients weigh the higher sensitivity of AMRI against its higher cost and potentially less desirable testing experience. PURPOSE: To assess patient preferences for hepatocellular carcinoma screening test attributes including sensitivity, false-positive rate, test-related anxiety, cost, and need for intravenous catheterization and contrast use, measured by choice-based conjoint analysis. MATERIALS AND METHODS: This was an ancillary study to two prospective dual-center studies designed to compare the hepatocellular carcinoma detection rates by ultrasound versus AMRI. Of the 135 eligible participants, 106 (median age 63, range 25-85; 56% male) completed the choice-based conjoint analysis survey and were included in this substudy. Participants' preference for individual screening test attributes was assessed using a 12-item, web-based choice-based conjoint analysis survey administered in person at the screening visit. Conjoint analyses software and hierarchical Bayes random-effects logit model were used to calculate the relative importance of each attribute. RESULTS: The most important attribute driving patient preferences was higher test sensitivity (importance score 39.8%), followed by lower cost (importance score 22.8%) and lower false-positive rate (importance score 19.4%). The overall estimated participants' preference for ultrasound and AMRI were similar when assuming the same specificity for both modalities. CONCLUSION: Higher screening test sensitivity and lower cost were the leading patient preference drivers. This study has important implications for understanding patient preferences for specific screening test characteristics as potential determinants of adherence.

Dynamic contrast-enhanced MRI perfusion quantification in hepatocellular carcinoma: comparison of gadoxetate disodium and gadobenate dimeglumine.

OBJECTIVES: (1) To assess the quality of the arterial input function (AIF) during dynamic contrast-enhanced (DCE) MRI of the liver and (2) to quantify perfusion parameters of hepatocellular carcinoma (HCC) and liver parenchyma during the first 3 min post-contrast injection with DCE-MRI using gadoxetate disodium compared to gadobenate dimeglumine (Gd-BOPTA) in different patient populations. METHODS: In this prospective study, we evaluated 66 patients with 83 HCCs who underwent DCE-MRI, using gadoxetate disodium (group 1, n = 28) or Gd-BOPTA (group 2, n = 38). AIF qualitative and quantitative features were assessed. Perfusion parameters (based on the initial 3 min post-contrast) were extracted in tumours and liver parenchyma, including model-free parameters (time-to-peak enhancement (TTP), time-to-washout) and modelled parameters (arterial flow (Fa), portal venous flow (Fp), total flow (Ft), arterial fraction, mean transit time (MTT), distribution volume (DV)). In addition, lesion-to-liver contrast ratios (LLCRs) were measured. Fisher's exact tests and Mann-Whitney U tests were used to compare the two groups. RESULTS: AIF quality, modelled and model-free perfusion parameters in HCC were similar between the 2 groups (p = 0.054-0.932). Liver parenchymal flow was lower and liver enhancement occurred later in group 1 vs group 2 (Fp, p = 0.002; Ft, p = 0.001; TTP, MTT, all p < 0.001), while there were no significant differences in tumour LLCR (max. positive LLCR, p = 0.230; max. negative LLCR, p = 0.317). CONCLUSION: Gadoxetate disodium provides comparable AIF quality and HCC perfusion parameters compared to Gd-BOPTA during dynamic phases. Despite delayed and decreased liver enhancement with gadoxetate disodium, LLCRs were equivalent between contrast agents, indicating similar tumour conspicuity. KEY POINTS: • Arterial input function quality, modelled, and model-free dynamic parameters measured in hepatocellular carcinoma are similar in patients receiving gadoxetate disodium or gadobenate dimeglumine during the first 3 min post injection. • Gadoxetate disodium and gadobenate dimeglumine show similar lesion-to-liver contrast ratios during dynamic phases in patients with HCC. • There is lower portal and lower total hepatic flow and longer hepatic mean transit time and time-to-peak with gadoxetate disodium compared to gadobenate dimeglumine.

Luminal Narrowing Alone Allows an Accurate Diagnosis of Crohn's Disease Small Bowel Strictures at Cross-Sectional Imaging.

BACKGROUND AND AIMS: Current consensus recommendations define small bowel strictures [SBS] in Crohn's disease [CD] on imaging as luminal narrowing with unequivocal upstream bowel dilation. The aim of this study was to [1] evaluate the performance of cross-sectional imaging for SBS diagnosis in CD using luminal narrowing with upstream SB dilation and luminal narrowing with or without upstream dilation, and [2] compare the diagnostic performance of computed tomography [CT] and magnetic resonance enterography [MRE] for SBS diagnosis. METHODS: In total, 111 CD patients [81 with pathologically confirmed SBS, 30 controls] who underwent CT and/or MRE were assessed. Two radiologists [R1, R2] blinded to pathology findings independently assessed the presence of luminal narrowing and upstream SB dilation. Statistical analysis was performed for [1] luminal narrowing with or without SB upstream dilation ['possible SBS'], and [2] luminal narrowing with upstream SB dilation ≥3 cm ['definite SBS']. RESULTS: Sensitivity for detecting SBS was significantly higher using 'possible SBS' [R1, 82.1%; R2, 77.9%] compared to 'definite SBS' [R1, 62.1%; R2, 65.3%; p < 0.0001] with equivalent specificity [R1, 96.7%; R2, 93.3%; p > 0.9]. Using the criterion 'possible SBS', sensitivity/specificity were equivalent between CT [R1, 87.3%/93.3%; R2, 83.6%/86.7%] and MRE [R1, 75.0%/100%; R2: 70.0%/100%]. Using the criterion 'definite SBS', CT showed significantly higher sensitivity [78.2%] compared to MRE [40.0%] for R1 but not R2 with similar specificities [CT, 86.7-93.3%; MRE, 100%]. CONCLUSION: SBS can be diagnosed using luminal narrowing alone without the need for upstream dilation. CT and MRE show similar diagnostic performance for SBS diagnosis using luminal narrowing with or without upstream dilation.

Transanal total mesorectal excision (taTME) for rectal cancer: beyond the learning curve.

BACKGROUND: Transanal total mesorectal excision (taTME) is a surgical approach for low rectal cancer with a learning curve estimated at 40-50 cases. The experience among taTME surgeons beyond their learning curve is limited. METHODS: A retrospective analysis of all taTME cases performed for rectal cancer at two tertiary care hospitals from 2014 to 2019 was conducted. Transanal surgeons had previously performed > 50 taTME cases. Demographic, perioperative, and short-term outcomes were analyzed. RESULTS: Among 54 taTME patients, 74.1% were male and 27.8% had a BMI ≥ 30. Tumors were stage I (8), II (13), III (29), and IV (4). Complex cases included 4 local recurrences, 4 prior liver resections, and 2 with prior prostate cancer. Thirty tumors were located ≤ 6 cm from the anal verge. On staging MRI, 12 had a positive predicted circumferential radial margin (+CRM), and 4 had internal anal sphincter involvement (+IAS). Forty-seven patients received neoadjuvant therapy. A 2-team approach was used in 51 patients with laparoscopic (83.3%) or robotic (16.7%) abdominal assistance with a 9.2% conversion rate. Low anterior resection with sphincter salvage was achieved in 87% with 8 patients requiring intersphincteric resection. Anastomoses were hand-sewn in 57.4% and all patients were diverted. Median LOS was 5 days with a 42.6% 30-day morbidity rate and 3 postoperative mortalities (ARDS, pulmonary embolism and pseudomembranous colitis). Complete and near complete TME grade was achieved in 94.4% with a 3.7% rate of +CRM. At a median follow-up of 28 months, local and distant recurrence rates were 3.9% and 17.6%, respectively, with no cancer-related mortality. CONCLUSION: Indications for taTME at experienced centers have expanded to include complex reoperative cases, local recurrences, metastatic cancer, and tumors with threatened CRM or IAS with evidence of post-treatment tumor regression. In the latter cases, taTME achieves good short-term outcomes and may facilitate R0 resection.