Faculty Bibliography

PURPOSE/OBJECTIVE:Hyperdense adnexal lesions on conventional CT often necessitate follow-up imaging. Photon counting CT (PCCT) allows for the generation of virtual unenhanced (VUE) and iodine map images. The purpose was to investigate the utility of PCCT spectral reconstructions to distinguish enhancing from nonenhancing hyperdense adnexal lesions. METHODS:A retrospective Picture Archiving and Communication System (PACS) search identified adult women with adnexal lesions on contrast-enhanced PCCT and with pelvic MRI or ultrasound within 180 days characterizing the lesion, the reference standard. Patients with adnexal lesions > 1 cm and > 20 Hounsfield Units (HU) on 70 keV PCCT images were included. Two radiologists drew region-of-interest measurements independently on adnexal lesions on thin-client software. Attenuation on VUE and 70 keV images, iodine density (ID), and iodine density normalized to aortic enhancement (NID) were recorded from the same region-of-interest. Attenuation change (ΔHU) from VUE to 70 keV was computed. Wilcoxon rank-sum test was used to compare ID, NID, and ΔHU for enhancing versus nonenhancing lesions. Receiver-operating characteristic (ROC) curves were used to determine optimal thresholds for enhancement. Inter-reader agreement was assessed with intraclass correlation coefficients (ICC). RESULTS:38 women (median [Interquartile Range (IQR)] age: 44[37,48]) were included. 22 had nonenhancing and 16 had enhancing lesions. ΔHU for enhancing and nonenhancing lesions was 27[24,37]HU and 2[-1,5]HU, respectively (p<.001). ID of enhancing and nonenhancing lesions was 1.15[0.98,1.60] mg/ml and 0.05[-0.08,0.18] mg/ml, respectively (p<.001). NID of enhancing and nonenhancing lesions was 22[14,29]% and 1.0[-1.0,3.0]%, respectively (p<.001). The optimal ΔHU for detecting enhancement at 70 keV was 12.0HU with 100% sensitivity and 95% specificity (Area Under the Curve (AUROC) = 0.99[95% Confidence Interval (CI): 0.97,1.00]). 0.4 mg/mL ID and 8% NID both had 100% sensitivity and 95% specificity (AUROC = 0.99[95%CI: 0.97,1.00]; AUROC = 0.99[95% CI: 0.96,1.00]; respectively). ICC[95% CI] was 0.74[0.56,0.86]. CONCLUSION/CONCLUSIONS:Attenuation change utilizing VUE images and iodine quantification can differentiate enhancing from nonenhancing hyperdense adnexal lesions at PCCT with excellent diagnostic performance. Accurate assessment of hyperdense adnexal lesion enhancement on PCCT may negate the need for follow-up imaging.

With the rapid growth of the use of computed tomography, advances in artificial intelligence enable opportunistic screening, the systematic extraction of clinically meaningful biomarkers from imaging scans performed for other indications. Modeling studies demonstrate that opportunistic screening can be highly cost effective by enabling early intervention and preventing complications such as osteoporotic fractures. Musculoskeletal radiologists are uniquely positioned to contribute to this paradigm shift because routine examinations frequently include vertebrae, skeletal muscle, adipose tissue, and vasculature, all structures that provide quantitative data on bone mineral density, sarcopenia, adiposity, and cardiovascular risk. However, widespread implementation faces challenges, such as the need for prospective outcomes data, normative reference standards, workflow integration, and clear pathways for clinical follow-up. This review examines the rationale, technical foundations, key applications, and challenges for opportunistic screening in musculoskeletal radiology.

OBJECTIVE:To retrospectively compare the follow-up imaging recommendation rate in patients who underwent an abdominopelvic PCCT, dual-source dual-energy CT (DECT), or single-energy CT (SECT). METHODS:A retrospective PACS search identified all outpatient contrast-enhanced abdominal PCCT, DECT, and SECT from 4/11/2022-10/14/2024. PCCT and DECT examinations without virtual noncontrast and iodine map images in PACS were excluded. All radiology reports were reviewed for follow-up imaging recommendations and reason. Follow-up imaging recommendation rates were compared across all three scanner groups and pairwise between each scanner type. The projected cost savings related to avoided follow-up recommendations with PCCT compared with SECT was calculated using the average Medicare reimbursement for each potential follow-up examination. RESULTS:16,065 examinations (median(IQR) age: 66(54-76) years; 8,433 females (52%)) including 8,246 PCCT, 3,988 DECT, and 3,831 SECT were included. Follow-up imaging was recommended in 8.1% (671/8,246) of PCCT, 8.7% (347/3,988) of DECT, and 13% (517/3,831) of SECT (p < .001). MRI was recommended in 5.2% (430/8,246) of PCCT, 4.2% (166/3,988) of DECT, and 6.4% (245/3,831) of SECT (p < .001). CT was recommended in 2.0% (168/8,246) of PCCT, 3.9% (155/3,988) of DECT, and 5% (193/3,831) of SECT (p < .001). Ultrasound was recommended in 1.4% (114/8,246) of PCCT, 1.2% (48/3,988) of DECT, and 2.7% (104/3,831) of SECT (p < .001). The total estimated cost savings of avoided subsequent imaging examinations with abdominopelvic PCCT compared with SECT was $32,904 for MRI, $71,085 for CT, and $10,888 for ultrasound, with $114,877 overall projected savings. CONCLUSION/CONCLUSIONS:There were significantly reduced follow-up imaging recommendations after abdominopelvic PCCT and DECT than SECT, with projected cost savings.

Photon counting computed tomography offers spectral capabilities on every scan, significant radiation exposure reductions with improved image quality, and improved spatial resolution. Spectral reconstructions, such as iodine maps and virtual non-contrast images improve the diagnostic capabilities of CT. In the emergency department, photon counting CT has proven benefits in assessing acute conditions, characterizing incidental masses and renal stones. In this review, we highlight some of the benefits of photon counting CT as it pertains to emergency abdominal imaging.

Opportunistic screening leverages existing imaging examinations performed for unrelated routine clinical indications to systematically extract quantitative biomarkers. Artificial intelligence tools have made deployment at scale increasingly feasible. However, the pathway from a validated algorithm to a functioning clinical program remains poorly defined, and prospective implementation at scale is uncommon. Successful deployment requires coordinated engagement from radiologists, information technology and operational teams, and clinical care teams, each facing distinct decisions that determine whether a program functions reliably and delivers patient benefit. This article presents a practical framework for opportunistic screening implementation organized around these three stakeholder groups. We apply this framework to opportunistic CT osteoporosis screening, drawing on our experience developing such a program at a large academic medical center. The framework presented is intended to be broadly applicable across opportunistic screening applications as the field moves from algorithmic validation toward clinical translation.

As Crohn disease treatment rapidly evolves, imaging has a critical role in treatment response assessment and clinical decision making. Therapy is often "top down," with the most powerful and potent therapies selected first. Disease activity assessment remains multifactorial, integrating source data from biomarkers, symptoms, endoscopy, and imaging. The "treat-to-target" approach also integrates these markers to escalate, de-escalate, or switch therapies. Given the transmural nature of Crohn disease, endoscopic mucosal healing (ie, the current treatment target) may not be sufficient evidence of remission, and imaging assessment of transmural healing could prove a better predictor of treatment response and long-term patient outcomes. Quantitative imaging methods have been developed to standardize treatment response assessment, including emerging radiologic techniques such as contrast-enhanced US, T1 mapping at MRI, standardized stricture assessment, and velocity-encoded phase contrast imaging. Morphologic changes of resolving inflammation at imaging may lag behind clinical response, and complete normalization of inflamed bowel segments may occur infrequently. In these cases, evaluating changes in bowel motility may be may be more helpful for detection of early treatment response. The radiologist is critical in the assessment of Crohn disease, providing insight into disease management and endoscopically occult and subclinical inflammation. The goal of this article is to highlight the role of imaging in driving management of Crohn disease, including endoscopically occult and subclinical disease, transmural healing, and treatment decision making in patients undergoing biologic therapies. ^©RSNA, 2026 See the invited commentary by Srinivasan and Taylor in this issue.

Background MR enterography (MRE) is increasingly used to guide treatment and improve outcomes in Crohn disease (CD). An abbreviated MRE (A-MRE) protocol-omitting contrast and antiperistaltic agents-may reduce scanning time and cost and improve compliance. Purpose To compare intrareader concordance and interreader agreement in detecting disease activity and disease-related complications using contrast-enhanced MRE (CE-MRE) versus an A-MRE protocol in participants with CD. Materials and Methods In this secondary analysis of a prospective study, 10 abdominal radiologists independently reviewed MRE examinations from a prospective study of participants with CD before and after treatment with biologics, using both A-MRE and CE-MRE protocols, at least 1 month apart. Interreader agreement and intrareader concordance were assessed using Gwet first agreement coefficient (AC1) at both the segment and participant levels for the presence of active inflammation, associated indicative features, and complications. Diagnostic accuracy of the simplified MR index of activity (sMaRIA) was evaluated against ileocolonoscopy when available. Results This study included 60 participants (median age, 36 years [IQR, 28-44 years]; 40 female; 80 examinations). Interreader agreement for detecting intestinal active disease was high and comparable between A-MRE and CE-MRE at the participant level (AC1, 0.87 [95% CI: 0.79, 0.95] vs 0.91 [95% CI: 0.85, 0.97]). For strictures, similar interreader agreement was observed between protocols (AC1: A-MRE, 0.61 [95% CI: 0.47, 0.74] vs CE-MRE, 0.50 [95% CI: 0.35, 0.65]). For penetrating complications, the interreader agreement was also similar between protocols (A-MRE, 0.71 [95% CI: 0.56, 0.86] vs CE-MRE, 0.76 [95% CI: 0.63, 0.90]). The intrareader concordance between protocols for detecting active inflammation and CD complications was almost perfect for all readers (AC1 range, 0.86-1.00). In the terminal ileum, sMaRIA showed high sensitivity (A-MRE, 96.4%; CE-MRE, 98.4%) and specificity (A-MRE, 68.1%; CE-MRE, 71.4%) for detecting inflammation. Conclusion An A-MRE protocol demonstrated comparable interreader agreement to conventional CE-MRE and high intrareader concordance for detecting active CD and related complications in participants with CD. © The Author(s) 2026. Published by the Radiological Society of North America under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Ohliger in this issue.

Ultrasound is the standard first-line imaging modality for hepatocellular carcinoma (HCC) screening; however, in certain patient populations, sensitivity is limited, and thus alternative strategies are needed in these patients. This article will provide an overview of MR imaging and computed tomography (CT) for the screening of HCC, with an emphasis on abbreviated MR imaging protocols and recent advancements in CT technology (dual energy and photon-counting CT).