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PurposeTo investigate the value of T2-radiomics combined with anatomical MRI staging criteria from pre-treatment rectal MRI in predicting complete response to neoadjuvant chemoradiation therapy (CRT).MethodsThis retrospective study included patients with locally advanced rectal cancer who underwent rectal MRI before neoadjuvant CRT from October 2011 to January 2015 and then surgery. Surgical histopathologic analysis was used as the reference standard for pathologic complete response. Anatomical MRI staging criteria were extracted from our institutional standardized radiology report. In radiomics analysis, one radiologist manually segmented the primary tumor on T2-weighted images for all 102 patients (i.e., training set); two different radiologists independently segmented 66/102 patients (i.e., validation set). 108 radiomics features were extracted. Then, scanner-independent features were identified and least absolute shrinkage operator analysis was used to extract a radiomics score. Finally, a support vector machine model combining the radiomics score and anatomical MRI staging criteria was compared against both anatomical MRI-only and radiomics-only models using the deLong test.ResultsThe study included 102 patients (42 women; median age = 61 years).The radiomics score produced an area under the curve (AUC) of 0.75. Comparable results were found using the validation set (AUCs = 0.75 and 0.71 for each radiologist, respectively). The anatomical MRI-only model had an accuracy of 67% (sensitivity 42%, specificity 72%); when adding the radiomics score, the accuracy increased to 74% (sensitivity 58%, specificity 77%).ConclusionCombining T2-radiomics and anatomical MRI staging criteria from pre-treatment rectal MRI may help to stratify patients based on the prediction of treatment response to neoadjuvant therapy.

PurposeSome patients with novel coronavirus disease 2019 (COVID-2019) present with abdominal symptoms. Abdominal manifestations of COVID on imaging are not yet established. The goal of this study was to quantify the frequency of positive findings on abdominopelvic CT in COVID-positive patients, and to identify clinical factors associated with positive findings to assist with imaging triage.Materials and methodsThis retrospective study included adult COVID-positive patients with abdominopelvic CT performed within 14 days of their COVID PCR nasal swab assay from 3/1/2020 to 5/1/2020. Clinical CT reports were reviewed for the provided indication and any positive abdominopelvic findings. Demographic and laboratory data closest to the CT date were recorded. Multivariate logistic regression model with binary outcome of having no reported positive abdominopelvic findings was constructed.ResultsOf 141 COVID-positive patients having abdominopelvic CT (average age 64 years [± 16], 91 [64%] women), 80 (57%) had positive abdominopelvic findings. Abdominal pain was the most common indication, provided in 54% (43/80) and 74% (45/61) of patients with and without reported positive abdominopelvic findings, respectively (p = 0.015). 70% (98/141) of patients overall had reported findings in the lung bases. Findings either typical or intermediate for COVID were reported in 50% (40/80) and 64% (39/61) of patients with and without positive abdominopelvic findings, respectively (p = 0.099). Of 80 patients with positive abdominopelvic findings, 25 (31%) had an abnormality of gastrointestinal tract, and 14 (18%) had solid organ infarctions or vascular thromboses. In multivariate analysis, age (OR 0.85, p = 0.023), hemoglobin (OR 0.83, p = 0.029) and male gender (OR 2.58, p = 0.032) were independent predictors of positive abdominopelvic findings, adjusted for race and Charlson comorbidity index.ConclusionAbdominopelvic CT performed on COVID-positive patients yielded a positive finding in 57% of patients. Younger age, male gender, and lower hemoglobin were associated with higher odds of having reportable positive abdominopelvic CT findings.

Objective To interrogate the mesorectal fat using MRI radiomics feature analysis in order to predict clinical outcomes in patients with locally advanced rectal cancer. Methods This retrospective study included patients who underwent neoadjuvant chemoradiotherapy for locally advanced rectal cancer from 2009 to 2015. Three radiologists independently segmented mesorectal fat on baseline T2-weighted axial MRI. Radiomics features were extracted from segmented volumes and calculated using CERR software, with adaptive synthetic sampling being employed to combat large class imbalances. Outcome variables included pathologic complete response (pCR), local recurrence, distant recurrence, clinical T-category (cT), post-treatment T category (ypT), and post-treatment N category (ypN). A maximum of eight most important features were selected for model development using support vector machines and fivefold cross-validation to predict each outcome parameter via elastic net regularization. Diagnostic metrics of the final models were calculated, including sensitivity, specificity, PPV, NPV, accuracy, and AUC. Results The study included 236 patients (54 ± 12 years, 135 men). The AUC, sensitivity, specificity, PPV, NPV, and accuracy for each clinical outcome were as follows: for pCR, 0.89, 78.0%, 85.1%, 52.5%, 94.9%, 83.9%; for local recurrence, 0.79, 68.3%, 80.7%, 46.7%, 91.2%, 78.3%; for distant recurrence, 0.87, 80.0%, 88.4%, 58.3%, 95.6%, 87.0%; for cT, 0.80, 85.8%, 56.5%, 89.1%, 49.1%, 80.1%; for ypN, 0.74, 65.0%, 80.1%, 52.7%, 87.0%, 76.3%; and for ypT, 0.86, 81.3%, 84.2%, 96.4%, 46.4%, 81.8%. Conclusion Radiomics features of mesorectal fat can predict pathological complete response and local and distant recurrence, as well as post-treatment T and N categories. Key Points • Mesorectal fat contains important prognostic information in patients with locally advanced rectal cancer (LARC). • Radiomics features of mesorectal fat were significantly different between those who achieved complete vs incomplete pathologic response (accuracy 83.9%, 95% CI: 78.6–88.4%). • Radiomics features of mesorectal fat were significantly different between those who did vs did not develop local or distant recurrence (accuracy 78.3%, 95% CI: 72.0–83.7% and 87.0%, 95% CI: 81.6–91.2% respectively).

PurposeTo predict microsatellite instability (MSI) status of colon cancer on preoperative CT imaging using radiomic analysis.MethodsThis retrospective study involved radiomic analysis of preoperative CT imaging of patients who underwent resection of stage II–III colon cancer from 2004 to 2012. A radiologist blinded to MSI status manually segmented the tumor region on CT images. 254 Intensity-based radiomic features were extracted from the tumor region. Three prediction models were developed with (1) only clinical features, (2) only radiomic features, and (3) “combined” clinical and radiomic features. Patients were randomly separated into training (n = 139) and test (n = 59) sets. The model was constructed from training data only; the test set was reserved for validation only. Model performance was evaluated using AUC, sensitivity, specificity, PPV, and NPV.ResultsOf the total 198 patients, 134 (68%) patients had microsatellite stable tumors and 64 (32%) patients had MSI tumors. The combined model performed slightly better than the other models, predicting MSI with an AUC of 0.80 for the training set and 0.79 for the test set (specificity = 96.8% and 92.5%, respectively), whereas the model with only clinical features achieved an AUC of 0.74 and the model with only radiomic features achieved an AUC of 0.76. The model with clinical features alone had the lowest specificity (70%) compared with the model with radiomic features alone (95%) and the combined model (92.5%).ConclusionsPreoperative prediction of MSI status via radiomic analysis of preoperative CT adds specificity to clinical assessment and could contribute to personalized treatment selection.

Objectives To determine the short-term outcomes of discordant tumor assessments between DWI-MRI and endoscopy in patients with treated rectal cancer when tumor-bed diffusion restriction is present (“+DWI”). Methods In this HIPPA-compliant, IRB-approved retrospective study, rectal MRI and endoscopic reports were reviewed for patients with locally advanced primary rectal adenocarcinoma (LARC) treated with chemoradiotherapy or total neoadjuvant therapy and imaged between January 2016 and December 2019. Eligible patients had a +DWI and endoscopy within 2 weeks of each other. True positive MRI were those with tumor on endoscopy and/or biopsy (TP a ) or in whom endoscopy was negative for tumor, but subsequent 3-month follow-up endoscopy and DWI were both positive (TP b ). The positive predictive value of DWI-MRI was calculated on a per-scan and per-patient basis. DWI-negative MRI exams were not explored in this study. Results In total, 397 patients with nonmetastatic primary LARC were analyzed. After exclusions, 90 patients had 98 follow-up rectal MRI studies with +DWI. Seventy-six patients underwent 80 MRI scans and had concordant findings at endoscopy (TPa). Seventeen patients underwent 18 MRI scans and had discordant findings at endoscopy (FP); among these, 4 scans in 4 patients were initially false positive (FP) but follow-up MRI remained +DWI and the endoscopy turned concordantly positive (TP b ). PPV was 0.86 per scan and per patient. In 4/18 (22%) scans and 4/17 (24%) patients with discordances, MRI detected tumor regrowth before endoscopy. Conclusions Although most +DWI exams discordant with endoscopy are false positive, 22% will reveal that DWI-MRI detects tumor recurrence before endoscopy. Key Points • Most often, in post-treatment assessment for rectal cancer when DWI-MRI shows restriction in the tumor bed and endoscopy shows no tumor , +DWI MRI will be proven false positive. • Conversely, our study demonstrated that, allowing for sequential follow-up at a 3-month maximum interval, DWI-MRI may detect tumor presence in the treated tumor bed before endoscopy in 22% of discordant findings between DWI-MRI and endoscopy. • Our results showed that a majority of DWI-MRI-positive scans in treated rectal cancer concur with the presence of tumor on endoscopy performed within 2 weeks.

Purpose To determine whether the administration of a microenema immediately prior to rectal magnetic resonance imaging (MRI) decreases the level of gas-related artifacts on diffusion-weighted imaging (DWI) sequences. Methods This retrospective analysis included 492 (183 baseline and 309 post-total neoadjuvant treatment [TNT]) consecutive MRI scans for rectal cancer from January 2019 to January 2020. Scan-related factors were identified including microenema use (yes or no), field of view (FOV) in DWI ( b  = 800 or b  = 1500), and magnet strength (1.5 T or 3 T). Two readers scored DWI studies for gas-related artifacts and T2-weighted sequences for the amount of intraluminal gas on a 5-point scale. Fisher’s exact test and the Rao–Scott Chi-squared test were used to examine associations between microenema use and other factors. Generalized estimating equation and multivariable regression models were performed to examine the effect of microenema use in subgroups of scans for each reader. Cohen’s κ was used to assess inter-reader agreement. Results Gas-related artifact levels decreased in scans with microenema overall ( P  < 0.001) as well as when scans were stratified by FOV ( P  ≤ 0.003). For both readers, post-TNT scans with microenema showed lower artifact levels overall ( P  < 0.014 and P  < 0.001) and in post-TNT subgroups of axial DWI scans ( P  ≤ 0.006 and P  < 0.001) and scans acquired with a 3 T magnet ( P  ≤ 0.001 for both FOV). No evidence of decreased artifact level was found for baseline studies. Decreased gas was seen with microenema use ( P  < 0.001 for both readers). Inter-reader agreement on artifact-level and gas-level assessments ranged from slight to substantial ( κ  = 0.273–0.685). Conclusion Microenema use prior to rectal MRI reduces gas-related artifacts on DWI, including both large and small FOV sequences and particularly on post-TNT scans performed at 3 T, and offers a viable solution to improve DWI quality.

Purpose To determine the most accurate measurement technique to assess rectal tumor height on MRI using two different anatomic landmarks for the anal verge. Introduction Accurate measurements and standardized reporting of MRI for rectal cancer staging is essential. It is not known whether measurements starting from the internal anal sphincter (IAS) or external anal sphincter (EAS) more closely correlate with tumor height from the anal verge on endoscopy. Methods This retrospective study included baseline staging MRI examinations for 85 patients after exclusions. Two radiologists blinded to endoscopic results measured the distance of rectal tumors from the internal anal sphincter and external anal sphincter on sagittal T2 images. The reference standard was endoscopic measurement of tumor height; descriptive statistics were performed. Results For reader 1, the mean difference in measurement of tumor height between MRI and endoscopy was − 0.45 cm (SD ± 1.76 cm, range − 6.0 to 3.9 cm) for the IAS and 0.51 cm (SD ± 1.75 cm range − 4.7 to 4.8 cm) for the EAS. For reader 2, the mean difference in measurement of tumor height between MRI and endoscopy was − 0.57 (STD ± 1.81, range − 5.9 to 4.8 cm) for the IAS and 0.52 cm (STD ± 1.85, range − 4.3 to 5.6 cm) for the EAS. Interobserver ICC was excellent between reader 1 and reader 2 for measurements from both the IAS (0.955 95% CI 0.931–0.97) and EAS (0.952, 95% CI 0.928, 0.969). Conclusion Measurement of tumor height on MRI was highly reproducible between readers; beginning measurements from the EAS tends to slightly overestimate tumor height on average and from the IAS tends to slightly underestimate tumor height on average.

PurposeTo compare the sensitivity, specificity and intra-observer and inter-observer agreement of pelvic magnetic resonance imaging (MRI) b800 and b1500 s/mm2 sequences in the detection of residual adenocarcinoma after neoadjuvant chemoradiation (CRT) for locally advanced rectal cancer (LARC).IntroductionDetection of residual adenocarcinoma after neoadjuvant CRT for LARC has become increasingly important and relies on both MRI and endoscopic surveillance. Optimal MRI diffusion b values have yet to be established for this clinical purpose.MethodsFrom our MRI database between 2018 and 2019, we identified a cohort of 28 patients after exclusions who underwent MRI of the rectum before and after neoadjuvant chemoradiation with a protocol that included both b800 and b1500 s/mm2 diffusion sequences. Four radiologists experienced in rectal MRI interpreted the post-CRT MRI studies with either b800 DWI or b1500 DWI, and a minimum of 2 weeks later re-interpreted the same studies using the other b value sequence. Surgical pathology or endoscopic follow-up for 1 year without tumor re-growth was used as the reference standard. Descriptive statistics compared accuracy for each reader and for all readers combined between b values. Inter-observer agreement was assessed using kappa statistics. A p value of 0.05 or less was considered significant.ResultsWithin the cohort, 19/28 (67.9%) had residual tumor, while 9/28 (32.1%) had a complete response. Among four readers, one reader had increased sensitivity for detection of residual tumor at b1500 s/mm2 (0.737 vs. 0.526, p = 0.046). There was no significant difference between detection of residual tumor at b800 and at b1500 for the rest of the readers. With all readers combined, the pooled sensitivity was 0.724 at b1500 versus 0.605 at b800, but this was not significant (p = 0.119). There was no difference in agreement between readers at the two b value settings (67.8% at b800 vs. 72.0% at b1500), or for any combination of individual readers.ConclusionAside from one reader demonstrating increased sensitivity, no significant difference in accuracy parameters or inter-observer agreement was found between MR using b800 and b1500 for the detection of residual tumor after neoadjuvant CRT for LARC. However, there was a suggestion of a trend towards increased sensitivity with b1500, and further studies using larger cohorts may be needed to further investigate this topic.

A T1 sequence on routine baseline staging rectal magnetic resonance imaging (MRI) is thought to help detect bone lesions. Our primary aim was to evaluate the incidence of bone lesions encountered on baseline staging rectal MRI, particularly the prevalence of bone metastases. This retrospective study included patients with rectal adenocarcinoma who underwent baseline rectal MRI at our institution between January 2010 and December 2017. The MRI report was reviewed for presence of bone lesions. When found, lesion type, presence of axial T1 non-fat-suppressed sequence, primary tumor T-stage, and presence of other organ metastases were recorded. In the absence of bone biopsy, the reference standard was follow-up imaging via computed tomography (CT), MRI, and/or positron emission tomography/CT (PET/CT) ≥ 1 year after the baseline MRI. The Wilcoxon rank-sum test and Fisher's exact test were used to compare clinicopathologic data of patients with malignant or benign bone lesions. A total of 1197 patients were included. 62/1197 patients (mean age 56.8 years (SD: 13.8), with 39 men) had bone lesions on baseline imaging, with 6 being bone metastases (0.5%, 95% CI 0.2%–1.1%). Of the 6 patients with bone metastases, 5/6 had other metastases (i.e., liver, lung) at baseline. Bone metastases on baseline rectal MRI performed for rectal adenocarcinoma are extremely rare. Furthermore, bone metastases without other organ (i.e., liver, lung) involvement is extremely rare.

ObjectivesTo investigate what findings are new on contrast-enhanced abdominopelvic CT in patients infected with SARS-CoV-2.MethodsContrast-enhanced CT of the abdomen and pelvis of patients with COVID-19 at a tertiary oncologic center acquired over a 2-month period were reviewed independently by two readers and scored for new imaging abnormalities compared with a prior scan. CT scans were included if the study was performed between − 3 and 45 days from the time of COVID-19 diagnosis. Clinical information was gathered from the medical records.ResultsA total of 63 patients (34 male, 29 female; mean age 60.6 years, range 24.4–85.0 years) were included in this retrospective cross-sectional study. Aside from new ground glass opacities seen at the lung bases (29/63, 46.0%), the most common findings were new thickening of the stomach, small bowel or colon or fluid-filled colon (14/63, 22.2%), new small volume ascites (7/63, 14.3%), gallbladder distention in those without prior cholecystectomy (3/43, 7.0%), and single cases each of acute pancreatitis (1/63, 1.6%) as well as new portal vein thrombosis (1/63, 1.6%).ConclusionAside from lung base ground glass opacities, the most common new imaging abnormality on abdominopelvic CT in patients with COVID-19 finding in our cohort was abnormalities of the gastrointestinal tract, followed by small volume ascites, gallbladder distention, and isolated cases of pancreatitis and portal vein thrombosis. These findings overlap with those previously reported that did not have a prior scan for comparison, and provide supportive evidence that some of these findings may be related to SARS-CoV-2 infection.