Faculty Bibliography

As therapeutic options to treat rectal cancers have advanced over the last several decades, MRI has become the standard of care for baseline local tumor and nodal staging of rectal cancers. An understanding of the technique, anatomy, tumor appearance, and elements of staging on MRI is essential to provide prognostic information and to guide neoadjuvant chemoradiation and surgical treatment. We provide a framework for imaging the rectum on MRI followed by a practical case-based approach to interpretation of pre-treatment MRI of the rectum in evaluation of rectal cancers, with examples and illustrations of the range of local tumor (T) stage and nodal (N) disease involvement. This approach can be paired with standardized reporting templates to support clear, accurate and clinically relevant imaging assessment of rectal cancers.

OBJECTIVES/OBJECTIVE: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:). 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:). 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/CONCLUSIONS:• 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 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.

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:sequences in the detection of residual adenocarcinoma after neoadjuvant chemoradiation (CRT) for locally advanced rectal cancer (LARC). INTRODUCTION:Detection 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. METHODS: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. RESULTS:(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. CONCLUSION:Aside 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.

PURPOSE:To identify the imaging manifestations of splenic involvement in babesiosis, a potentially fatal tick-borne zoonosis with multi-organ involvement. METHODS:In our single center HIPAA compliant IRB-approved study, we performed a retrospective search of the electronic medical record at our institution to identify all patients with known or suspected acute babesiosis from 2000 to 2017. We then reviewed all abdominal imaging of patients with confirmed disease to identify incidence and characteristics of splenic involvement. Splenomegaly was determined using a height- and gender-adjusted reference. RESULTS:After exclusions, 63 patients with a confirmed diagnosis of babesiosis and contemporaneous imaging of the spleen were included in the final cohort. Within this cohort, 56 (89%) had splenomegaly at a minimum and 13 had splenic infarcts. Splenic rupture was present in eight patients with three having a pseudoaneurysm. In 14 patients with follow-up imaging, the spleen subsequently diminished in size. One additional patient with ruptured spleen underwent emergency splenectomy prior to imaging. CONCLUSION:Although the literature suggests splenic involvement is a rare finding, acute parasitemia with babesiosis commonly affects the spleen. Recognition of this association can aid radiologists diagnosing splenic involvement in babesiosis and can lead to appropriate intervention in the minority with splenic hemorrhage.

PURPOSE:To 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). METHODS:This 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. RESULTS:The 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%). CONCLUSION:Combining 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.

To present a novel use of a portable computed tomography (CT) for evaluation of COVID-19 patients presenting to an urgent care center (UCC). Infection control is imperative for hospitals treating patients with COVID-19, even more so in cancer centers, where the majority of the patient population is susceptible to adverse outcomes from the infection. Over the past several weeks, our department has worked to repurpose a portable CT scanner from our surgical colleagues that operates with fixed-parameters to perform non-contrast, helical, thin-slice chest imaging to address the known pulmonary complications of COVID-19. Despite the technical limitations of the portable CT unit that was repurposed for the UCC, diagnostic-quality images in an acute care setting were successfully obtained. Repurposing of a portable CT scanner for use in COVID-19 patients offers a feasible option to obtain diagnostic quality images while minimizing the risk of exposing other patients and hospital staff to an infected patient.

BACKGROUND:Colitis-associated cancers (CAC) are a catastrophic complication of inflammatory bowel disease; at diagnosis, CAC is frequently at an advanced stage. Although the genomic alterations (GA) in CAC are different from sporadic colorectal cancer (CRC), the same systemic therapies are used. We compared clinically relevant outcomes using standard care systemic chemotherapy of stage IV CAC versus a matched patient control cohort of stage IV CRC patients. PATIENTS AND METHODS:A retrospective matched cohort design was used. Eighteen cases of stage IV CAC (7 ulcerative colitis, 11 Crohn disease) and 18 CRC were identified. GA analysis was available for all patients. Outcome endpoints included response rate and response duration, progression-free survival, and OS. RESULTS:Although the response rates were similar (CAC 35.7% vs. CRC 57.1%, P = .45), the median duration of response for CAC was significantly shorter (1.4 months, vs. CRC 11.8 months, P = .006). There was no difference in dose density of first-line therapy between cohorts, suggesting that shorter response duration was due to more rapid development of chemotherapy resistance. Median OS was significantly shorter for CAC patients (13 vs. 27.6 months, P = .034). As expected, there was a difference in the spectrum of GA between CAC and CRC cohorts. However, GA associated with poor prognosis (eg, B-Raf) were no more frequent in the CAC cohort. CONCLUSION:Clinically meaningful outcomes of duration of response and OS are worse for CAC versus sporadic CRC patients treated with FOLFOX or FOLFIRI as first therapy for metastatic disease.