Faculty Bibliography

Photon-counting CT (PCCT) offers new opportunities for abdominal imaging by enabling higher spatial resolution, improved image quality, and reduced radiation exposure compared with conventional energy-integrating detector CT systems. However, standardized PCCT protocols for abdominal imaging are lacking, which limits clinical adoption, comparability across institutions, and multicenter research studies. The Society of Abdominal Radiology (SAR) Photon-Counting Detector CT Emerging Technology Commission created a survey to achieve consensus on common adult abdominal PCCT protocols for the FDA-approved PCCT, including portal venous phase CT, multiphase aortic CTA, and multiphase pancreas CT protocols. The survey included the following items for each protocol: scan mode, tube potential, image quality level, primary viewing virtual monoenergetic imaging (VMI) level, reconstruction kernel, additional VMI or other spectral reconstructions sent to PACS, and details of archiving the special spectral image dataset. Consensus statements were generated based on the survey and voted upon by nine radiologists from nine institutions using the consensus-minus-one method. Consensus was reached for 20 protocol features, including that 70-keV VMI is recommended for primary interpretation of portal venous and multiphase pancreas PCCT and that, for multiphase aortic CTA, low virtual monoenergetic levels should be viewed. This multiinstitutional consensus endorsed by SAR establishes standardized abdominal PCCT protocols.

BACKGROUND/UNASSIGNED:In patients with inflammatory bowel disease (IBD) who need intestinal resection, prior data suggest that earlier surgical intervention may be associated with improved outcomes. However, surgery is often deferred for additional trials of advanced therapies, which potentially shifts patients from a fit to a frail preoperative state. OBJECTIVES/UNASSIGNED:This study aimed to evaluate clinical changes that occur in the year prior to intestinal resection in patients with IBD. DESIGN/UNASSIGNED:Retrospective cohort study. METHODS/UNASSIGNED:This was a multi-hospital retrospective study of patients ⩾18 years old who underwent initial IBD-related intestinal resection between January 1, 2018 and May 31, 2023. Clinical characteristics and radiographical skeletal muscle mass were compared using the Wilcoxon Signed-Rank test for continuous variables and McNemar's test for categorical variables. RESULTS/UNASSIGNED: = 0.06). CONCLUSION/UNASSIGNED:In the 6-12 months prior to an IBD-related intestinal resection, as compared to the month prior, individuals were less likely to be malnourished, have an infection, or need hospitalization for IBD. This suggests that minimizing delays to surgery may lead to improved outcomes.

More than half of patients with Crohn disease will develop strictures. Strictures are areas of bowel luminal narrowing composed of a combination of inflammatory cells, muscular hypertrophy, and fibrosis. Most patients with strictures eventually require endoscopic or surgical intervention. This article reviews small bowel Crohn disease stricture histopathology, current imaging definitions and challenges, and stricture management. Current imaging-based stricture definitions use different criteria and do not recognize strictures without upstream dilation nor failed endoscopic passage. This consensus was endorsed by the Society of Abdominal Radiology and developed by the Society of Abdominal Radiology Inflammatory Bowel Disease Disease Focused Panel as well as gastroenterology and pathology experts in Crohn disease strictures. Updated imaging stricture definitions and recommendations are presented. Most importantly, the panel now defines a Crohn disease small bowel stricture using a threshold small bowel dilation of 2.5 cm (rather than 3.0 cm) and incorporates failed endoscopic passage, even when there is no associated bowel dilation at CT or MR enterography. With these updated imaging stricture definitions, it is hoped that patients with Crohn disease may benefit from more timely stricture identification and management.

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.

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: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.

OBJECTIVE:To determine the optimal virtual monoenergy for viewing the bowel at photon-counting CT enterography using quantitative assessment of mural attenuation, contrast-to-noise ratio, signal-to-noise ratio and noise. METHODS:This study was institutional review board approved and Health Insurance Portability and Accountability Act compliant. Consecutive adults (≥ 18 years) who underwent photon-counting CT enterography from 5/1/2022-5/31/2022 with available Spectral Postprocessing (SPP) images for retrospective virtual monoenergy creation were identified. Nine virtual monoenergetic series (40-120 keV, 10 keV increments) were created. Two region-of-interest measurements were placed in the stomach wall, jejunum wall, ileum wall, and each psoas muscle by two radiologists on 0.6 mm images in PACS. Region-of-interests were copied to other virtual monoenergies to ensure identical placement and size. Attenuation (HU) and noise (HU standard deviation) were recorded from each region-of-interest. Signal-to-noise ratio and contrast-to-noise ratio were computed for stomach, jejunum, ileum, and all bowel combined. Pairwise comparisons for attenuation, noise, signal-to-noise ratio and contrast-to-noise ratio for each virtual monoenergy were performed with ANOVA. A p <.05 indicated statistical significance. RESULTS:50 patients (32 female; mean[SD] age: 57 years) were included. Attenuation and noise for all bowel regions were highest at 40 keV with statistically significant pairwise comparisons from 40 to 70 keV (all p <.05), but similar for 70-120 keV (all p >.05). Signal-to-noise ratio was similar from 40 to 70 keV (all p >.05) for all bowel regions. Contrast-to-noise ratio decreased with increasing keV. Contrast-to-noise ratio was similar for all bowel at 40 keV and 50 keV (p =.06), for stomach from 40 to 70 keV (all p >.05), for jejunum from 40 to 50 keV (p =.21), and for ileum from 40 to 60 keV (all p >.05). CONCLUSION/CONCLUSIONS:50 keV virtual monoenergetic images from photon-counting CT enterography optimizes contrast-to-noise ratio while mitigating noise and should routinely be utilized for bowel assessment at photon-counting CT enterography. As most photon-counting CT users primarily interpret virtual monoenergetic images in clinical practice, knowledge of the optimal virtual monoenergy can inform protocol development.

As photon-counting CT (PCCT) gains wider clinical acceptance and is implemented in more practice settings, guidance for implementing this cutting-edge imaging modality in its currently clinically available form (NAEOTOM Alpha; Siemens Healthineers) is needed. Understanding the core physics of PCCT, particularly the nuances in detector technology, is paramount for achieving optimal imaging system setup and proficient image acquisition. Through a comprehensive overview of PCCT physics and real-life case examples to highlight the technologic differences from conventional energy-integrating detector CT systems, the radiologist will be able to effectively implement PCCT in clinical practice. The key steps taken when starting a successful PCCT imaging practice across radiology subspecialties includes (a) imaging system setup; (b) protocol development, emphasizing the critical role of tailored protocols in achieving diagnostic precision and radiation dose optimization and introducing new terminology; (c) the imaging process, highlighting the importance of optimizing scan modes to suit clinical requirements; and (d) postimaging considerations, including the interpretation of system outputs and the judicious selection of images for routine transmission to the picture archiving and communication system. This article serves as a reference for radiologists, technologists, medical physicists, and informatics teams seeking to harness the full potential of PCCT. By optimizing workflow and facilitating adept image interpretation, this guidance aims to augment diagnostic capabilities and elevate the standard of patient care in the era of PCCT.

PURPOSE/OBJECTIVE:As the pancreas is a low contrast visibility organ, pancreatic ductal adenocarcinoma detection is challenging due to subtle attenuation differences between tumor and pancreatic parenchyma. Photon counting CT (PCCT) has superior iodine contrast-to-noise ratio than conventional CT and also affords the creation of low keV virtual monoenergetic images, both of which increase adenocarcinoma conspicuity. The purpose therefore was to identify the optimal virtual monoenergy for visualizing PDAC during the pancreatic parenchymal phase of enhancement at PCCT using both quantitative and qualitative analyses. METHODS:Consecutive patients with pancreatic parenchymal phase PCCT source data were retrospectively identified by PACS search. For the quantitative analysis, region of interest (ROI) measurements were drawn in the pancreatic head, body, tail, pancreatic adenocarcinoma (if present), and psoas muscles on 40-120 keV virtual monoenergetic images in 10 keV increments. Based on the quantitative analysis results and vendor recommendations, four virtual monoenergies(40 keV, 55 keV, 70 keV, and 85 keV) were selected for additional qualitative analysis. Three radiologists blinded to four virtual monoenergies assessed overall image quality, image noise, pancreatic enhancement, and pancreatic mass conspicuity on 5-point Likert scales. RESULTS:54 patients (28/54 male, mean[SD] age: 62 [13] years) were included. Quantitatively, 40 keV had the highest pancreatic parenchymal CNR and attenuation difference between the adenocarcinoma and parenchyma, but also the highest noise (HUsd). Qualitatively, 70 keV had the best overall image quality (Mean [SE]: 3.7[0.1]) and lower noise than 40 and 55 keV (3.6[0.08] vs. 1.8[0.07] and 2.7[0.05], respectively, p < .001). 40 keV had the greatest pancreatic enhancement (mean[SE] 4.6[0.11]). Adenocarcinoma conspicuity ratings were greatest at 40 keV and 55 keV, and not significantly different from each other (mean[SE] 4.4[0.13] and 4.3[0.14], respectively, Tukey adj-p =.20). 55 keV had greater overall image quality and lower noise than 40 keV (mean[SE] 3.4[0.08] vs. 2.5[0.08], Tukey adj-p < .001 and 2.7[0.05] vs. 1.8[0.07], Tukey adj-p < .001 respectively). CONCLUSION/CONCLUSIONS:55 keV pancreatic parenchymal phase virtual monoenergetic images afford optimal pancreatic assessment at PCCT for the visualization of pancreatic adenocarcinoma. Routinely viewing 55 keV virtual monoenergetic images at PCCT may improve PDAC detection.