Faculty Bibliography

The evaluation of patients with gastrointestinal (GI) bleeding is complicated due to the variety of tests available and the large number of potential causes of bleeding. MRI is less commonly used than computed tomography and endoscopy but it can diagnose disease that causes GI bleeding and serve as a complementary role to other tests. MRI is most often used in the form of magnetic resonance enterography (MRE) to assess patients with suspected bleeding from the small bowel. While CT enterography (CTE) and video capsule endoscopy (VCE) are the more commonly used tests in the setting of GI Bleeding, MRE has characteristics which may make it the more favorable modality for a given patient. Potential advantages of MRE, protocol considerations and the literature delineating its diagnostic performance for detecting pathology which can cause GI bleeding relative to CTE and VCE are reviewed here. MRI is uncommonly used to assess patients with upper GI bleeding, lower GI bleeding and patients with bleeding sites that remain undetected despite a formal evaluation of the GI tract, however it may add value in specific clinical scenarios. These uncommon scenarios and specific clinical examples are also presented to highlight the potential benefits of MRI.

OBJECTIVE:To assess photon counting CT iodine density as a marker of histopathologic treatment response after neoadjuvant chemotherapy in patients with pancreatic ductal adenocarcinoma. MATERIALS AND METHODS/METHODS:A retrospective PACS search identified 21 pancreatic ductal adenocarcinoma patients [14 men; mean (SD) age: 64 (10) y] who underwent neoadjuvant chemotherapy and pancreatic photon counting CT 2 months before resection from April 11, 2022 to February 2, 2024. The histopathologic treatment response grade was the reference standard. Freehand regions-of-interest measurements were drawn independently by 2 radiologists as large as possible within the mass on pancreatic parenchymal phase images. Attenuation, iodine density, and iodine density normalized to the aorta were recorded. Mann-Whitney U test was used to compare attenuation, iodine density, and normalized iodine density for responders (pathologic grade 1, 2) versus nonresponders (grade 3). Receiver operating characteristic curves were created, and optimal thresholds were determined with Youden's index. A P<0.05 indicated statistical significance. RESULTS:Thirteen of 21 (61.9%) patients showed pathologic treatment response. Iodine density for nonresponders and responders was mean (SD) 0.47 (0.23) mg/mL and 1.20 (0.75) mg/mL, respectively (P=0.005). Normalized iodine density for nonresponders and responders was 7.6 (5.5)% and 22.5 (16.0)%, (P=0.006). Attenuation for nonresponders and responders was 56.5 (10.9) HU and 70.6 (17.7) HU, (P=0.04). Upon receiver operating characteristic analysis, an iodine density threshold of 0.65 mg/mL had 77% sensitivity and 88% specificity (AUC=0.86), and a normalized iodine density threshold of 10.1% had 77% sensitivity and 88% specificity (AUC=0.86) for treatment response. A 61.8 HU threshold had 77% sensitivity and 75% specificity (AUC=0.78). CONCLUSIONS:Elevated iodine density correlates with pancreatic ductal adenocarcinoma histopathologic treatment response with high specificity. Photon counting CT iodine density may be used as a marker of histopathologic treatment response.

This document serves to update the 2018 ACR Appropriateness Criteria® colorectal screening guidance document. In light of new recommendations from the US Preventative Services Task Force (USPSTF), an updated literature review of the imaging procedures for the screening of colorectal cancer was performed. Average-risk, elevated-risk, and high-risk individuals as well as those individuals who had an incomplete colonoscopy or were unable to tolerate colonoscopy were included. CT colonography without contrast was found to be usually appropriate for individuals at average and elevated risk between 45 to 75 years of age at initial screening. Additionally, CT colonography without contrast was found to be usually appropriate in individuals at average risk, elevated risk, and at high risk after incomplete colonoscopy or unable to tolerate colonoscopy. Other imaging procedures such as barium fluoroscopy and CT of the abdomen and pelvis were usually not appropriate. CT colonography without contrast, barium fluoroscopy, and CT of the abdomen and pelvis were usually not appropriate in high-risk individuals who can undergo a complete colonoscopy. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

This document aims to provide recommendations on the role of imaging in the diagnosis of squamous cell anal cancer, focusing on its use in locoregional and systemic assessment during initial staging, posttreatment evaluation, and surveillance. For initial locoregional staging, MRI of the pelvis and FDG-PET/CT are usually appropriate to complement clinical and digital rectal examinations, because they offer additional information regarding locoregional tumor invasion and nodal metastases. For metastatic disease assessment, which is rare in the initial presentation and commonly associated with recurrence-with lymph nodes, liver, and lungs being the most common sites of disease-CT and FDG-PET/CT are usually appropriate for detecting distant nodal metastases and other sites of metastatic disease. MRI of the abdomen may be appropriate as a problem-solving tool, particularly in assessing small or indeterminate liver lesions. For patients who have completed locoregional treatment, most typically achieve clinical complete response; consequently, few require surgery unless there is persistent disease or recurrence. The role of posttreatment imaging assessment is still debatable; however, in cases in which surgery is indicated, MRI and FDG-PET/CT are usually appropriate for assessing local tumor invasion and nodal metastases. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

BACKGROUND:Abdominal computed tomography (CT) is commonly performed in adults. Abdominal aortic calcification (AAC) can be visualized and quantified using artificial intelligence (AI) on CTs performed for other clinical purposes (opportunistic CT). We sought to investigate the value of AI-enabled AAC quantification as a predictor of coronary artery disease and its association with cardiovascular events. METHODS:A fully automated AI algorithm to quantify AAC from the diaphragm to aortic bifurcation using the Agatston score was retrospectively applied to a cohort of patient that underwent both non-contrast abdominal CT for routine clinical care and cardiac CT for coronary artery calcification (CAC) assessment. Subjects were followed for a median of 36 months for major adverse cardiovascular events (MACE, composite of death, myocardial infarction [MI], ischemic stroke, coronary revascularization) and major coronary events (MCE, MI or coronary revascularization). RESULTS:Our cohort included 3599 patients (median age 60 years, 62% male, 74% white) with an evaluable abdominal and cardiac CT. There was a positive correlation between presence and severity of AAC and CAC (r=0.56, P<0.001). AAC showed excellent discriminatory power for detecting or ruling out any CAC (AUC for PREVENT risk score 0.701 [0.683 to 0.718]; AUC for PREVENT plus AAC 0.782 [0.767 to 0.797]; P<0.001). There were 324 MACE, of which 246 were MCE. Following adjustment for the 10-year cardiovascular disease PREVENT score, the presence of AAC was associated with a significant risk of MACE (adjHR 2.26, 95% CI 1.67-3.07, P<0.001) and MCE (adjHR 2.58, 95% CI 1.80-3.71, P<0.001). A doubling of the AAC score resulted in an 11% increase in the risk of MACE and a 13% increase in the risk of MCE. CONCLUSIONS:Using opportunistic abdominal CTs, assessment of AAC using a fully automated AI algorithm, predicted CAC and was independently associated with cardiovascular events. These data support the use of opportunistic imaging for cardiovascular risk assessment. Future studies should investigate whether opportunistic imaging can help guide appropriate cardiovascular prevention strategies.

Dual-energy computed tomography (DECT) has been available for clinical use since 2006. Since its clinical debut, multiple different dual energy systems have been developed including sequential acquisition, rapid-switching, dual-source, and twin-beam, in addition to spectral imaging techniques such as dual-layer and photon counting CT. While the specifics of these techniques vary, the underlying principles remain the same; by acquiring at least two data sets, material specific information in each image voxel can be determined. Most commonly used to evaluate for the presence or absence of iodine, DECT has found clinical applications in the assessment of gastrointestinal bleeding, bone marrow edema, the characterization of renal stones, and the accurate evaluation of vascular stenosis, among other uses. This review aims to familiarize the radiologist with the theoretical basis underlying DECT, describe the different types of DECT including the relative strengths and weaknesses of each, and highlight specific clinical applications for which DECT may be valuable.

BACKGROUND & AIMS/OBJECTIVE:Perianal fistulising Crohn's disease (pfCD) affects one-fifth of patients with Crohn's disease (CD), significantly affecting their quality of life. Magnetic resonance imaging is the gold standard for evaluating fistula healing in pfCD, but variability in radiological definitions hampers meaningful clinical interpretation and consistent trial design. This study aimed to establish an international consensus on the definition of radiological healing in pfCD. METHODS:The study was conducted in 2 phases. Phase 1 involved a systematic review to identify magnetic resonance imaging-based variables and indices used to define healing in pfCD, assessing methodological quality using the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) framework. Phase 2 utilized a 2-round online Delphi consensus process with 84 international experts, followed by a stakeholder meeting to achieve consensus (agreement threshold >80%). Results were reported as per Accurate Consensus Reporting Document (ACCORD) guidelines. RESULTS:A radiologically healed fistula can be defined by the absence of T2-weighted hyperintensity, a completely fibrotic fistula tract and, when contrast is used, the absence of contrast enhancement on post-contrast T1-weighted images (95% consensus). Radiological improvement of a fistula can be defined (80% consensus) by the presence of a least one essential criterion: an increasingly fibrotic fistula tract, an unequivocal reduction in one or more of the following: T2-weighted hyperintensity, fistula diameter, fistula length, abscess size, or contrast enhancement of the fistula tract. CONCLUSION/CONCLUSIONS:This international Delphi consensus standardizes radiological endpoints in pfCD, improving consistency in clinical and research settings. Future studies will validate this definition and assess how radiological changes predict long-term clinical outcomes and quality of life improvements.

PURPOSE/OBJECTIVE:Retrospectively compare image quality, radiologist diagnostic confidence, and time for images to reach PACS for contrast enhanced abdominopelvic CT examinations created on the scanner console by technologists versus those generated automatically by thin-client artificial intelligence (AI) mechanisms. METHODS:A retrospective PACS search identified adults who underwent an emergency department contrast-enhanced abdominopelvic CT in 07/2022 (Console Cohort) and 07/2023 (Server Cohort). Coronal and sagittal multiplanar reformatted images (MPR) were created by AI software in the Server cohort. Time to completion of MPR images was compared using 2-sample t-tests for all patients in both cohorts. Two radiologists qualitatively assessed image quality and diagnostic confidence on 5-point Likert scales for 50 consecutive examinations from each cohort. Additionally, they assessed for acute abdominopelvic findings. Continuous variables and qualitative scores were compared with the Mann-Whitney U test. A p < .05 indicated statistical significance. RESULTS:Mean[SD] time to exam completion in PACS was 8.7[11.1] minutes in the Console cohort (n = 728) and 4.6[6.6] minutes in the Server cohort (n = 892), p < .001. 50 examinations in the Console Cohort (28 women 22 men, 51[19] years) and Server cohort (27 women 23 men, 57[19] years) were included for radiologist review. Age, sex, CTDlvol, and DLP were not statistically different between the cohorts (all p > .05). There was no significant difference in image quality or diagnostic confidence for either reader when comparing the Console and Server cohorts (all p > .05). CONCLUSION/CONCLUSIONS:Examinations utilizing AI generated MPRs on a thin-client architecture were completed approximately 50% faster than those utilizing reconstructions generated at the console with no statistical difference in diagnostic confidence or image quality.