Markus M. Obmann

Objectives: To evaluate the impact of contrast phase, age, and sex on CT-derived body composition metrics—specifically attenuation and volume of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), liver, and skeletal muscle. The potential of the proportion of muscle voxels below 0 Hounsfield units (HU) as a surrogate for fatty infiltration was also explored. Materials and Methods: A retrospective analysis of 866 multiphasic abdominal CT scans (non-enhanced [NE], arterial [ART], portal venous [PV]) from 2012 to 2022 was performed. Segmentation of SAT, VAT, liver, and skeletal muscle was conducted using the AI-based TotalSegmentator. Wilcoxon signed-rank tests and Bland–Altman analysis (mean bias and 95% limits of agreement) were applied to assess contrast-related effects; Spearman’s correlation coefficient was used to assess demographic associations. Results: Significant variation in attenuation and volume of SAT, VAT, and muscle was observed across contrast phases (p < 0.001). SAT attenuation was higher in NE and PV than in ART, while VAT attenuation was highest in PV. SAT volume increased and VAT volume decreased in contrast-enhanced phases. Attenuation and volume showed strong inter-phase correlation (ρ > 0.9). VAT attenuation was significantly higher in females, whereas VAT volume was significantly greater in males. VAT volume negatively correlated with liver attenuation (ρ = −0.33). Muscle voxels <0 HU were significantly reduced in contrast-enhanced scans. Conclusions: Contrast phase, age, and sex significantly influence CT-based body composition parameters. These confounding factors should be considered when using quantitative imaging biomarkers in clinical and research settings.

Purpose: To investigate whether an AI-based approach combining deep learning myocardial segmentation with attenuation-normalized myocardial mapping (colormaps) improves detection of myocardial ischemia and infarction on emergency ECG-gated CT angiography. Materials and Methods: In this retrospective study, 119 patients with acute chest pain who underwent ECG-gated CT angiography to exclude pulmonary embolism or acute aortic syndrome and invasive coronary angiography within 48 h were included. A deep learning model (nnU-Net) was used for automatic left-ventricular myocardial segmentation, serving as the basis for voxel-wise attenuation normalization to generate AI-based myocardial attenuation maps. Six readers with varying experience levels evaluated all cases for myocardial hypoattenuation in a multi-reader, multi-case design, with and without AI-generated attenuation maps. Results: AI-based myocardial attenuation mapping increased mean sensitivity for detection of myocardial ischemia or infarction by 12% [IQR 2–20%] compared with standard CT interpretation alone. Sensitivity improved by 15% [IQR 10–22%] in STEMI (ST-Elevation Myocardial Infarction) and 11% [IQR −1–18%] in NSTEMI (Non-STEMI) cases. The AI-assisted approach resulted in the correct reclassification of 11% of patients and improved inter-reader agreement, particularly among less experienced readers, demonstrating reduced reader dependency. Conclusions: AI-based myocardial segmentation and attenuation mapping enhance the detection of myocardial ischemia and infarction on emergency CT angiography and improve inter-reader agreement. This AI-assisted image processing approach provides clinically meaningful decision support in acute chest pain imaging workflows.

Objectives: To determine whether a dual-energy CT (DECT) protocol—including arterial and portal-venous phases, virtual non-contrast (VNC) images, and iodine maps—provides non-inferior diagnostic performance to a conventional triphasic CT protocol for gastrointestinal (GI) bleeding. Materials and methods: In this retrospective single-center diagnostic accuracy study, we included all patients who underwent triphasic abdominal CT for GI bleeding between September 2015 and June 2024. For each case, conventional and DECT datasets were generated. Three fellowship-trained abdominal radiologists and two residents independently assessed all cases for active GI bleeding. A consensus review served as the reference standard. Sensitivity and specificity were compared using the Wald method for paired confidence intervals (non-inferiority margin 3%). Diagnostic confidence and reading time were analyzed using the Wilcoxon signed-rank test. Inter-reader agreement was assessed with Fleiss’ kappa. Results: One hundred patients (mean age, 70 ± 14 years; 34 women) were evaluated, including 50 with GI bleeding (21 upper, 29 lower) and 50 controls. With conventional triphasic CT, sensitivity and specificity were 91.6% and 94.4%, respectively. With DECT, they were 94.4% and 96.0%, demonstrating non-inferiority within a 3% margin. Diagnostic confidence increased from 4 (IQR, 4–5) to 5 (IQR, 4–5) ( p < 0.01). Mean reading time decreased from 96.3 s to 93.6 s ( p < 0.01), also meeting non-inferiority. Inter-reader agreement was almost perfect (κ = 0.82). Total DLP was reduced by 20% when true non-contrast images were omitted. Conclusion: DECT-derived VNC and iodine maps provide non-inferior diagnostic performance to conventional CT for GI bleeding and can replace true non-contrast imaging. Key Points: Question Eliminating true non-contrast scans from CT protocols for gastrointestinal bleeding could reduce radiation dose, but its impact on diagnostic performance remains unclear. Findings Dual-energy CT with virtual non-contrast images and iodine maps achieved non-inferior sensitivity, specificity, reading time, and diagnostic confidence compared to conventional triphasic CT. Clinical relevance Dual-energy CT with virtual non-contrast images and iodine maps can reliably replace true non-contrast scans in GI bleeding protocols, maintaining diagnostic performance while reducing radiation exposure—offering a safer and more efficient diagnostic alternative for patients. Graphical

Objectives: To evaluate the clinical value of low-field MRI compared to routine radiography in patients with painful total hip arthroplasty (THA) and to clarify its diagnostic advantages. Methods: Forty-eight patients (68 ± 14 years, 25 female) with THA and equivocal hip pain who underwent both low-field MRI and standard radiographs were retrospectively included. Magnetic resonance (MR) images were acquired on a 0.55 T system between May 2021 and April 2022. Two fellowship-trained musculoskeletal radiologists reviewed radiographs and MR images. MRI findings not apparent on radiographs were graded on a 5-point patient management relevance scale (0 = none, 1 = unlikely, 2 = unclear, 3 = probably, and 4 = definitely). Results: Twenty-nine (60%) patients demonstrated additional relevant pathologies on low-field MRI. Fourteen findings were rated as “probably” and 15 as “definitely” relevant for further patient management. Definitely relevant findings identified only on MRI were periprosthetic lysis (n = 6), occult periprosthetic (n = 3) and pelvic ring fractures (n = 2), suspected periprosthetic joint infection due to periprosthetic fluid collections (n = 2), and tendon/muscle ruptures with secondary hematoma (n = 2). Lower grade findings included iliopsoas tendon lesions (splitting, low-grade partial tearing, and bursitis) in 13 patients, and extensive fatty muscle atrophy of the gluteal muscles (Goutallier 3 or 4) in 26 patients. Conclusion: More than half of the patients with equivocal hip pain following arthroplasty would have benefited from complementary low-field MRI at their initial presentation. Advances in knowledge: Half of the patients with an explanatory radiograph presented new, treatment-relevant MRI findings. Low-field MRI may be a reasonable addition to existing diagnostic algorithms.

Objectives: This study evaluates the advantages in diagnostic accuracy, confidence, and reading time of additional dual-energy CT-derived reconstructions for assessing acute bowel ischemia. Methods and materials: This retrospective study includes 25 patients with surgically proven acute bowel ischemia and 25 gender- and age-matched controls who underwent biphasic abdominal dual-energy CT. Two fellowship-trained abdominal radiologists and two residents evaluated all cases with and without additional dual-energy CT-derived iodine maps and virtual non-contrast images. Diagnostic confidence was rated on a 10-point Likert scale. Reading time was recorded. The inter-reader agreement was assessed using Fleiss’ kappa. Sensitivity and specificity were compared using McNemar’s test, reader confidence, and reading times with the Wilcoxon signed-rank test. Results: For conventional images alone, the inter-reader agreement was moderate (κ = 0.58), with a sensitivity of 77% (95% CI: 67.5–84.8%) and specificity of 90% (95% CI: 82.4–95.1%). Adding dual-energy CT images, inter-reader agreement increased to substantial (κ = 0.69), sensitivity increased significantly to 89% (95% CI: 81.2–94.4%, p = 0.02), while specificity increased non-significantly to 93% (95% CI: 86.1–97.1%, p = 0.51). Diagnostic confidence increased significantly from 8 (IQR: 6–8) to 9 (IQR: 8–9) (p < 0.01). Equivalent diagnostic accuracy and confidence increases were observed for fellowship-trained and resident radiologists. A non-significant increase in mean reading time per case from 196 s to 201 s was observed (p = 0.30). Conclusion: Additional dual-energy CT reconstructions increase diagnostic accuracy and confidence without increasing reading time when evaluating suspected acute bowel ischemia. Both experienced and resident readers benefit from dual-energy CT images. Key Points: Question There are too few clinical studies assessing the diagnostic accuracy of dual-energy CT (DECT) to recommend its use for evaluating suspected acute bowel ischemia. Findings Adding DECT-derived iodine maps and virtual-non-contrast images increase reader sensitivity and confidence while maintaining high specificity when evaluating for acute mesenteric ischemia. Clinical relevance Dual-energy CT should be used to investigate suspected acute bowel ischemia. Both diagnostic accuracy and confidence can be increased independent of reader experience without significantly increasing reading time.