Carotid atherosclerosis is a major contributor to ischemic stroke. While luminal stenosis has historically guided treatment decisions, growing evidence indicates that plaque composition, vascular inflammation and perivascular adipose tissue (PVAT) may be more closely linked to clinical outcomes and plaque vulnerability. This study aimed to characterize carotid PVAT using photon-counting computed tomography (PCCT) and to evaluate its spatial behavior and variability in a cohort of asymptomatic patients. We retrospectively analyzed PCCT angiography data from 20 asymptomatic patients. A custom-developed Python algorithm was used to segment concentric perivascular layers from 1 mm to 5 mm around the carotid artery. For each layer, we quantified attenuation values in Hounsfield Units (HU) and voxel counts. Statistical comparisons were performed across layers and between sides. Mean PVAT attenuation decreased progressively with increasing distance from the carotid wall. Significant differences were observed between inner and outer layers, particularly between the 1 mm and 3–5 mm annuli. Circle-by-circle analysis revealed substantial inter-individual variability in HU trends. Voxel count increased with annular thickness, but variability (SD and CV) also rose in outer layers. No significant differences were found between left and right carotid arteries in either attenuation or voxel distribution. Photon-counting CT enables detailed, layer-specific assessment of carotid PVAT. The observed attenuation patterns and inter-individual variability suggest that PVAT profiling may provide valuable insights into local vascular inflammation and plaque vulnerability. These findings support the potential of PCCT as a noninvasive tool for vascular risk stratification beyond luminal stenosis. Question Can photon-counting CT enable a reliable, layer-by-layer quantitative characterization of carotid perivascular adipose tissue in asymptomatic patients beyond luminal stenosis assessment? Findings Photon-counting CT demonstrated a progressive decrease in PVAT attenuation with increasing distance from the carotid wall and marked inter-individual variability across concentric layers. Clinical relevance Layer-specific PVAT profiling with photon-counting CT may provide a noninvasive imaging marker of local vascular inflammation, supporting improved carotid risk stratification beyond stenosis severity, even in asymptomatic individuals.

The purpose of this study was to evaluate whether a misalignment correction algorithm reduces artifacts from breathing in patients undergoing computed tomography angiography (CTA) early after coronary artery bypass graft (CABG) surgery. In this retrospective study, consecutive patients undergoing CTA early after CABG surgery between November 2023 and March 2025 were screened. Patients exhibiting relevant breathing artifacts on standard reconstructions were included for the evaluation. CTA was acquired in the ECG-gated sequential mode on a dual-source CT. For each patient, standard reconstructions were compared with those using a misalignment correction algorithm designed to resolve discontinuities between adjacent image stacks (ZeeFree). Two blinded readers assessed artifacts across six anatomical regions (bypass grafts, coronary arteries, thoracic aorta, pulmonary trunk, lung/trachea, and sternum) using a 4-point visual analogue scale. Among 680 patients scanned at a median of 4 days (IQR 2–8 days) after CABG surgery, 75 patients (11

Metallic implants can cause relevant artifacts in computed tomography (CT) imaging, affecting the quality and diagnostic utility of scans. Previous advancements in metal artifact reduction techniques have shown promise but still exhibit limitations in artifact reduction, particularly close to metal implants. To evaluate a novel, advanced iterative metal artifact reduction (iMAR) algorithm for photon-counting detector CT in an experimental study focused on visualizing the vicinity of a fixation nail implant. Three bovine femur bones with titanium-based trochanteric fixation nail implants were scanned on a clinical photon-counting detector CT scanner. Images were reconstructed (1) without iMAR, (2) with the current iMAR algorithm, and (3) with a new prototype iMAR algorithm. The new iMAR prototype algorithm advances state-of-the-art iMAR for photon-counting detector CT by utilizing intrinsically available spectral information. Attenuation and artifact severity (SD of attenuation) were quantified by placing regions-of-interest on each reconstruction across 3 different axial slices: One in the bone marrow immediately adjacent to the metal implant and one in the water adjacent to the femur with the implant. Qualitative image quality, newly introduced artifacts, and diagnostic confidence were rated by 3 radiologists using 5-point Likert scales. Differences between reconstructions were tested using the Friedman test with Wilcoxon post hoc tests; interreader agreement was assessed using Krippendorff alpha. Artifact severity in the bone adjacent to the implant significantly decreased from 226 HU (no iMAR) to 174 HU (current iMAR) and to 159 HU with the new iMAR ( P < 0.001). Adjacent to the femur, artifact severity decreased from 63 HU to 48 HU and to 29 HU, respectively ( P < 0.05). Qualitative scores differed significantly between reconstructions ( P < 0.05), with highest ratings for new iMAR across all categories. Current iMAR introduced new artifacts near the implant, which did not occur with new iMAR ( P < 0.05). Experimental evidence from a bovine femur implant model suggests that a new, advanced iterative metal artifact reduction algorithm leveraging intrinsic spectral information from photon-counting detector CT effectively reduces metal artifacts and further improves the visualization of the metal-bone interface. Thus, this technique has the potential to enhance the assessment of implant-related complications such as aseptic loosening.

This article, on the 60th anniversary of the journal Investigative Radiology , a journal dedicated to cutting-edge imaging technology, discusses key historical milestones in CT and MRI technology, as well as the ongoing advancement of contrast agent development for cardiovascular imaging over the past decades. It specifically highlights recent developments and the current state-of-the-art technology, including photon-counting detector CT and artificial intelligence, which will further push the boundaries of cardiovascular imaging. What were once ideas and visions have become today's clinical reality for the benefit of patients, and imaging technology will continue to evolve and transform modern medicine.

The expansion of cross-sectional imaging has led to a rise in the incidentally detected renal masses, including renal cell carcinomas (RCC). Though most incidentally detected renal masses are cysts, a clinical challenge is distinguishing cystic (often proteinaceous or hemorrhagic) from solid lesions, particularly when only a single phase examination is available. Spectral CT has the potential to offer advantages across different clinical applications in RCC. It has direct protocol implications, reducing the number of phases needed in CT urography or renal CT protocols, thereby lowering radiation dose while maintaining accuracy and cost-effectiveness. In addition, energy- and material-specific information can be extracted from a single data set, including quantitative data often regarded as surrogates of functional information (e.g., perfusion) that could be used to characterize renal lesions. Spectral CT imaging enables accurate distinction between cystic and solid renal masses. It could be a useful adjunct tool that improves characterization and monitoring, but it doesn't yet replace biopsy or histology, especially for subtype and grading, and may play an important role in post-treatment follow-up, assessment of therapy response, and differentiation of metastasis. Finally, PCCT offers the added advantages of improved spatial resolution and reduced contrast dose, image noise, and artifacts. PCCT may also enable new applications, such as K-edge imaging. The purpose of this article is to provide the reader with a summary of the technique's physics and its potential advantages, including both current and emerging applications in RCC.

OBJECTIVES:Quantification of liver fat on computed tomography (CT) is often confounded by hepatic iron deposition and the use of iodinated contrast agents. This phantom study aimed to evaluate the feasibility and accuracy of quantifying liver fat content (LFC) in the presence of iron using spectral localizer radiographs acquired with photon-counting detector CT (PCD-CT). MATERIALS AND METHODS:Sixteen liver phantoms were constructed using mixtures of liver tissue, fat, and iron to simulate 4 levels of LFC (0%, 10%, 30%, and 50%) and 4 levels of liver iron concentration (LIC: 0, 1.5, 3, and 6 mg/mL). Five additional reference phantoms (containing fat only, water only, or water-iron solutions) were included. All phantoms were scanned on a clinical PCD-CT system using 3 tube current settings (10, 50, 300 mA) to acquire spectral localizer radiography data. Material decomposition of high- and low-energy bin data yielded water and hydroxyapatite (HA) maps. HA values were analyzed as a function of LFC and LIC, and water values were correlated with corresponding HA values. RESULTS:Increasing LFC resulted in a linear decrease in HA values, consistent across all LIC levels (slopes=-0.0016 to -0.0023; mean=-0.0019; r=0.997 to 1.0). Conversely, increasing LIC caused a linear increase in HA values, independent of LFC (slopes=0.0147 to 0.017; mean=0.0156; r=0.978 to 1.0). When combined with water values in a 2-dimensional material space, these stable linear relationships enabled estimation of LFC irrespective of LIC. Findings were reproducible across all tube current settings. CONCLUSION:Spectral localizer radiographs from PCD-CT allow quantification of liver fat content even in the presence of iron deposition. If validated in vivo, this technique may enable low-threshold opportunistic screening for hepatic steatosis and iron overload from precontrast localizer scans.

OBJECTIVE:Bright-blood late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) is standard for myocardial scar detection, yet subendocardial infarcts may be difficult to identify due to limited scar-blood contrast. Grayscale inversion is a simple, vendor-independent post-processing technique that may enhance visual contrast. We assessed whether grayscale inversion improves diagnostic accuracy or reader confidence, and whether its effect varies by reader experience or scanner vendor. METHOD:In this single-center, multivendor study, 120 patients (90 with and 30 without ischemic scar) underwent 2D bright-blood LGE on GE, Philips, and Siemens 1.5 T scanners. Three short-axis slices per patient were evaluated in standard bright-blood and grayscale-inverted visualizations by nine readers (three per EACVI experience level). Readers assessed scar presence, transmurality, and diagnostic confidence (4-point scale). Consensus of two Level-3 experts served as reference. RESULTS:Across 34,560 segment-level assessments, diagnostic accuracy was high (91.5%, 95% CI 91.0-91.9%) and similar for standard vs. inverted images (90.7% vs. 91.9%, p = 0.27), with no differences across experience levels or in low-transmurality lesions. In contrast, reader confidence increased significantly with grayscale-inversion (3.25 ± 0.81 vs. 2.78 ± 0.88, p < 0.0001), with the greatest relative improvement among Level-1 readers (2.63 ± 0.89 → 3.00 ± 0.83, p < 0.001). Interobserver agreement and transmurality reproducibility remained unchanged. Results were consistent across vendors. CONCLUSION:Grayscale-inverted bright-blood LGE significantly increases reader confidence without compromising diagnostic accuracy or interobserver agreement. This simple, vendor-neutral technique may support training and improve interpretive certainty in routine clinical LGE assessment.

Background and purpose: Photon-counting detector computed tomography (PCD-CT) offers several image reconstruction options, e.g. virtual monoenergetic images (VMIs) and relative electron density (RED) images. This study investigated these PCD-CT reconstructions for dose calculation in head-and-neck cancer (HNC) patients. Materials and methods: 10 HNC patients referred to radiotherapy were scanned with PCD-CT. The same contouring and therapy strategy was followed as in the patients' clinical treatment, optimized on an energy-integrated-detector CT (EID-CT). 18 volumetric arc therapy treatment plans (6 MV photons) were optimized on RED images and recalculated on 70 keV VMI (VMI70), using the same amount of monitor units. While RED images did not require scanner-specific calibration, the conversion from CT number to RED for VMI70 was calibrated using a phantom with tissue-equivalent inserts with known RED. To assess the clinical impact of using RED maps with vendor-provided calibration, one plan per patient was recalculated using bulk material overrides. Plan quality was evaluated by evaluating dose-volume metrics, such as the dose to 98% of planning target volume, and compared between RED, VMI70, and EID-CT. Results: All plans optimized on RED images fulfilled the clinical goals. Dose-volume metrics differed by <3% between RED and VMI70 and <5% between RED and EID-CT. RED differed by differed by <4% from bulk density override (<1% when the target did not overlap with air volumes). Conclusions: Treatment planning can be accurately performed on PCD-CT images of HNC cases, using either VMI (after CT-number-to-RED conversion) or RED images (without scanner-specific calibration).

OBJECTIVE:To evaluate the feasibility of an optimized high-resolution three-dimensional (3D) double-echo steady-state (DESS) magnetic resonance imaging (MRI) sequence, combined with a dedicated 15-channel mandibular coil, on 3T MRI for visualization of the mandibular nerve and its six peripheral branches in healthy volunteers. STUDY DESIGN:Images from 21 participants were assessed by three readers with varying levels of experience and medical specialties. Overall image quality, artifact presence, and nerve continuity across the proximal and distal segments of the masseteric, buccal, auriculotemporal, lingual, inferior alveolar, and mylohyoid nerves were evaluated using 5-point visual rating scales (5 = best, 1 = worst). Descriptive statistics and inter-reader agreement using Krippendorff's alpha (α) were calculated. RESULTS:Image quality was consistently rated as excellent with minimal artifacts (median 5, IQR 5-5) and high inter-reader agreement (α = 0.87-0.92). Continuous visualization of proximal and distal segments was achieved for most branches, particularly the inferior alveolar and lingual nerves (median 5, IQR 5-5). Visualization of thinner branches, including the masseteric, mylohyoid, and buccal nerves, was more challenging (median 4-4.5). Overall inter-reader agreement for nerve continuity assessment ranged from good to perfect (α = 0.79-1.0). CONCLUSIONS:An optimized high-resolution 3D-DESS sequence, combined with a dedicated mandibular coil, enables reliable and reproducible visualization of the mandibular nerve and its peripheral branches.

BACKGROUND:Metallic implants can cause relevant artifacts in computed tomography (CT) imaging, affecting the quality and diagnostic utility of scans. Previous advancements in metal artifact reduction techniques have shown promise but still exhibit limitations in artifact reduction, particularly close to metal implants. PURPOSE:To evaluate a novel, advanced iterative metal artifact reduction (iMAR) algorithm for photon-counting detector CT in an experimental study focused on visualizing the vicinity of a fixation nail implant. METHODS:Three bovine femur bones with titanium-based trochanteric fixation nail implants were scanned on a clinical photon-counting detector CT scanner. Images were reconstructed (1) without iMAR, (2) with the current iMAR algorithm, and (3) with a new prototype iMAR algorithm. The new iMAR prototype algorithm advances state-of-the-art iMAR for photon-counting detector CT by utilizing intrinsically available spectral information. Attenuation and artifact severity (SD of attenuation) were quantified by placing regions-of-interest on each reconstruction across 3 different axial slices: One in the bone marrow immediately adjacent to the metal implant and one in the water adjacent to the femur with the implant. Qualitative image quality, newly introduced artifacts, and diagnostic confidence were rated by 3 radiologists using 5-point Likert scales. Differences between reconstructions were tested using the Friedman test with Wilcoxon post hoc tests; interreader agreement was assessed using Krippendorff alpha. RESULTS:Artifact severity in the bone adjacent to the implant significantly decreased from 226 HU (no iMAR) to 174 HU (current iMAR) and to 159 HU with the new iMAR (P < 0.001). Adjacent to the femur, artifact severity decreased from 63 HU to 48 HU and to 29 HU, respectively (P < 0.05). Qualitative scores differed significantly between reconstructions (P < 0.05), with highest ratings for new iMAR across all categories. Current iMAR introduced new artifacts near the implant, which did not occur with new iMAR (P < 0.05). CONCLUSION:Experimental evidence from a bovine femur implant model suggests that a new, advanced iterative metal artifact reduction algorithm leveraging intrinsic spectral information from photon-counting detector CT effectively reduces metal artifacts and further improves the visualization of the metal-bone interface. Thus, this technique has the potential to enhance the assessment of implant-related complications such as aseptic loosening.

OBJECTIVES:Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome and myocardial infarction. Accurate diagnosis is crucial for appropriate management. This study aimed to compare late enhancement (LE) imaging using photon-counting detector (PCD)-CT with cardiac MRI in patients with SCAD in the acute phase and during follow-up and to introduce a novel approach for visualizing myocardial extracellular volume (ECV) distribution in the myocardium. MATERIALS AND METHODS:This single-center prospective study enrolled patients with SCAD diagnosed with invasive coronary angiography. LE iodine imaging with spectral dual-source PCD-CT and cardiac MRI was performed early after symptom onset and at short-term follow-up. CT included coronary angiography and LE imaging (5 minutes after contrast). LE CT was assessed using the combination of conventional LE images, overlay images, polar maps, and with newly developed atlas maps. Atlas maps represent 2-dimensional maps with prefiltering applied to enable a simpler and more intuitive reading of ECV distribution across the myocardium. Cardiac MRI served as the reference standard for identifying pathologic myocardial segments based on late gadolinium enhancement (LGE) and edema on T2-weighted and T2-mapping images. Agreement between modalities was evaluated using Cohen's κ. RESULTS:Seventeen patients (median age, 44 years [interquartile range, 36-52]; 11 women) underwent 24 LE CT and cardiac MRI scans. Sixteen patients (median age, 44 years; 10 women) underwent acute phase imaging (median 6 days after symptom onset), and 8 patients (median age, 45 years; 6 women) underwent follow-up imaging (median 120 days after symptom onset). Atlas maps were helpful in detecting segments with pathological ECV and to adjudicate corresponding myocardial segments. Agreement between LE CT with LGE cardiac MRI was strong in the acute phase (κ = 0.832), improving to almost perfect when comparing LE-CT with both LGE and edema in cardiac MRI (κ = 0.944). At follow-up imaging, agreement further improved as edema resolved (κ = 0.956). CONCLUSIONS:LE imaging with PCD-CT demonstrated strong agreement with cardiac MRI for detecting myocardial injury in SCAD, which further improved at follow-up when edema resolved. Newly introduced atlas maps proved useful for a simple and intuitive visualization of myocardial injury.

Introduction This ex vivo study aimed to determine the optimal energy level for virtual monoenergetic imaging (VMI) using photon-counting detector computed tomography (PCD-CT) and to evaluate the effectiveness of iterative metal artifact reduction (iMAR) in assessing simulated endodontic challenges and complications. Methods Sixteen extracted third molars were simulated with one of eight distinct endodontic diagnostic challenges and imaged using PCD-CT at radiation doses equivalent to standard-dose cone-beam CT. VMIs were reconstructed from 70-190 keV at 10 keV increments, both with and without iMAR. Diagnostic accuracy, depiction quality of endodontic challenges, artifact severity, and visualization of key endodontic anatomical structures were independently assessed by 2 observers using a 5-point visual analogue scale (1 = least favourable, 5 = most favourable). Descriptive statistics were calculated, and inter-reader agreement was analysed using Krippendorff’s alpha coefficient. Results VMIs achieved excellent diagnostic accuracy (97%) and high-quality visualization of endodontic challenges (median: 5, IQRs: 4-5 or 4.25-5; α = 0.63-1.00) across the entire reconstructed energy spectrum (70-190 keV), with minimal artifacts, particularly at ≥ 110 keV (α = 1.0). Task-specific analysis demonstrated optimal visualization of caries at 70-80 keV and fractured files at 70-100 keV. For other pathologies, VMI at ≥100 keV effectively reduced artifacts without compromising anatomical detail. IMAR did not improve image quality and consistently reduced diagnostic performance. Conclusions VMI from PCD-CT provides high-quality imaging with minimal artifacts, well-suited for indication-specific endodontic diagnostics. Clinical Relevance PCD-CT supports novel, indication-specific workflows in endodontic imaging, potentially enhancing diagnostic precision and long-term treatment follow-up.

Abstract Objective To determine optimal reconstruction parameters for dental implant imaging using photon-counting detector CT (PCD-CT), including ultra-high-resolution (UHR) images, virtual monoenergetic images (VMI), and iterative metal artifact reduction (iMAR). Materials and methods In this ex vivo study, six pig mandibles were prepared with two titanium-based implants and imaged on a PCD-CT. Scans were reconstructed as UHR images and VMI from 70–190 keV at 10 keV increments with and without iMAR. Two independent readers qualitatively evaluated image quality and artifact severity using five-point visual rating scales (5 = excellent, no or minimal artifacts; and 1 = very poor, non-diagnostic, severe artifacts). Two readers quantified artifact severity, defined as the standard deviations in attenuation in regions of interest adjacent to the implants. Results UHR images without iMAR yielded high image quality (median 5 for both readers) with minor artifact severity (median 4 for both), whereas iMAR reduced image quality (median 3 for both). VMI without iMAR showed decreasing artifacts at higher energy levels. VMI at 120–130 keV achieved optimal image quality (median 5 for both readers at 120 keV, and medians 4 and 5 at 130 keV) with minimal artifacts (median 5 for both), whereas iMAR reduced quality. Quantitative artifact burden decreased with higher energy levels (from 200 HU at 70 keV to 113 HU at 190 keV), and no improvement was observed using iMAR. Conclusions PCD-CT effectively reduces metal-induced artifacts in dental implant imaging, with UHR images and VMI at 120–130 keV providing optimal image quality, while reconstructions with iMAR offered no further benefit. Relevance statement PCD-CT provides excellent dental implant visualization while minimizing the impact of metal artifacts. Key Points In this ex vivo study, ultra-high-resolution images and virtual monoenergetic images at 120–130 keV from PCD-CT effectively reduce metal artifacts from dental implants. Effective artifact reduction offers excellent visualization of the bone-implant interface. Iterative metal artifact reduction (iMAR) did not provide additional benefit for visualization of the bone-implant interface. Graphical Abstract

BACKGROUND:Blooming artifacts from calcified plaques can obscure the vessel lumen, leading to overestimation of stenosis severity. Spectral coronary angiography with photon-counting detector CT (PCD-CT) provides virtual monoenergetic images (VMIs) for coronary artery disease assessment. While VMIs at high VMI energy levels reduce calcium blooming, iodine contrast is diminished, limiting diagnostic value. This study evaluated whether contrast media with an atomic number higher than iodine (high-Z) preserve vascular contrast using high VMI energy levels, thereby improving the accuracy of stenosis quantification. METHODS:A phantom with 4 and 6 mm diameter rods to mimic small diameter vessels containing eccentric calcified plaques causing 25%, 50%, and 75% diameter stenoses was scanned with a dual-source PCD-CT system. Five different contrast media, including iodine, tungsten, holmium, hafnium, and bismuth, were tested. VMIs were reconstructed from 40 to 190 keV in 1-keV steps. Vessel attenuation, contrast-to-noise ratio (CNR), and stenoses were measured. Qualitative assessment of image quality was performed. RESULTS:Iodine attenuation was high at lower VMI energy levels and dropped below 250 HU at >100 keV. Tungsten, holmium, hafnium, and bismuth maintained >250 HU attenuation throughout the entire energy range. Vessel CNR of iodine was high at lower and decreased at higher VMI energy levels, similar to the CNR of holmium and bismuth, though to a lesser extent. In distinction, CNRs of tungsten and hafnium were lower at lower VMI energy levels and increased to a relatively constant level at higher keV. Tungsten CNR increased with energy, approaching ~40 at high keV. Across all contrast media and stenosis degrees, stenoses were overestimated on low VMI energy levels (24% to 32.5% at 40 keV), while the degree of overestimation decreased at higher VMI energy levels (0% to 13.5% at 190 keV). At 190 keV, tungsten, hafnium, and bismuth showed ≤2.5% stenosis overestimation, compared with iodine (10% to 13.5%). Image quality varied between contrast media and energy levels: new very high-Z contrast media achieved higher scores, while iodine peaked at lower keV (55 to 70 keV) and, due to loss of contrast at higher energies, received the lowest overall scores. CONCLUSIONS:As compared with iodine, very high-Z contrast media enable superior lumen definition and more accurate stenosis assessment, also at high VMI energy levels, which minimize calcium blooming.

OBJECTIVES:The aim of this study was to evaluate the feasibility and reproducibility of a novel deep learning (DL)-based coronary plaque quantification tool with automatic case preparation in patients undergoing ultra-high resolution (UHR) photon-counting detector CT coronary angiography (CCTA), and to assess the influence of temporal resolution on plaque quantification. MATERIALS AND METHODS:In this retrospective single-center study, 45 patients undergoing clinically indicated UHR CCTA were included. In each scan, 2 image data sets were reconstructed: one in the dual-source mode with 66 ms temporal resolution and one simulating a single-source mode with 125 ms temporal resolution. A novel, DL-based algorithm for fully automated coronary segmentation and intensity-based plaque quantification was applied to both data sets in each patient. Plaque volume quantification was performed at the vessel-level for the entire left anterior descending artery (LAD), left circumflex artery (CX), and right coronary artery (RCA), as well as at the lesion-level for the largest coronary plaque in each vessel. Diameter stenosis grade was quantified for the coronary lesion with the greatest longitudinal extent in each vessel. To assess reproducibility, the algorithm was rerun 3 times in 10 randomly selected patients, and all outputs were visually reviewed and confirmed by an expert reader. Paired Wilcoxon signed-rank tests with Benjamini-Hochberg correction were used for statistical comparisons. RESULTS:One hundred nineteen out of 135 (88.1%) coronary arteries showed atherosclerotic plaques and were included in the analysis. In the reproducibility analysis, repeated runs of the algorithm yielded identical results across all plaque and lumen measurements ( P > 0.999). All outputs were confirmed to be anatomically correct, visually consistent, and did not require manual correction. At the vessel level, total plaque volumes were higher in the 125 ms reconstructions compared with the 66 ms reconstructions in 28 of 45 patients (62%), with both calcified and noncalcified plaque volumes being higher in 32 (71%) and 28 (62%) patients, respectively. Total plaque volumes in the LAD, CX, and RCA were significantly higher in the 125 ms reconstructions (681.3 vs. 647.8  mm 3 , P  < 0.05). At the lesion level, total plaque volumes were higher in the 125 ms reconstructions in 44 of 45 patients (98%; 447.3 vs. 414.9  mm 3 , P  < 0.001), with both calcified and noncalcified plaque volumes being higher in 42 of 45 patients (93%). The median diameter stenosis grades for all vessels were significantly higher in the 125 ms reconstructions (35.4% vs. 28.1%, P  < 0.01). CONCLUSIONS:This study evaluated a novel DL-based tool with automatic case preparation for quantitative coronary plaque in UHR CCTA data sets. The algorithm was technically robust and reproducible, delivering anatomically consistent outputs not requiring manual correction. Reconstructions with lower temporal resolution (125 ms) systematically overestimated plaque burden compared with higher temporal resolution (66 ms), underscoring that protocol standardization is essential for reliable DL-based plaque quantification.

Objectives:Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome and myocardial infarction. Accurate diagnosis is crucial for appropriate management. This study aimed to compare late enhancement (LE) imaging using photon-counting detector (PCD)-CT with cardiac MRI in patients with SCAD in the acute phase and during follow-up and to introduce a novel approach for visualizing myocardial extracellular volume (ECV) distribution in the myocardium.Materials and Methods:This single-center prospective study enrolled patients with SCAD diagnosed with invasive coronary angiography. LE iodine imaging with spectral dual-source PCD-CT and cardiac MRI was performed early after symptom onset and at short-term follow-up. CT included coronary angiography and LE imaging (5 minutes after contrast). LE CT was assessed using the combination of conventional LE images, overlay images, polar maps, and with newly developed atlas maps. Atlas maps represent 2-dimensional maps with prefiltering applied to enable a simpler and more intuitive reading of ECV distribution across the myocardium. Cardiac MRI served as the reference standard for identifying pathologic myocardial segments based on late gadolinium enhancement (LGE) and edema on T2-weighted and T2-mapping images. Agreement between modalities was evaluated using Cohen's kappa.Results:Seventeen patients (median age, 44 years [interquartile range, 36-52]; 11 women) underwent 24 LE CT and cardiac MRI scans. Sixteen patients (median age, 44 years; 10 women) underwent acute phase imaging (median 6 days after symptom onset), and 8 patients (median age, 45 years; 6 women) underwent follow-up imaging (median 120 days after symptom onset). Atlas maps were helpful in detecting segments with pathological ECV and to adjudicate corresponding myocardial segments. Agreement between LE CT with LGE cardiac MRI was strong in the acute phase (kappa = 0.832), improving to almost perfect when comparing LE-CT with both LGE and edema in cardiac MRI (kappa = 0.944). At follow-up imaging, agreement further improved as edema resolved (kappa = 0.956).Conclusions:LE imaging with PCD-CT demonstrated strong agreement with cardiac MRI for detecting myocardial injury in SCAD, which further improved at follow-up when edema resolved. Newly introduced atlas maps proved useful for a simple and intuitive visualization of myocardial injury.

Background: Metal artifacts in computed tomography (CT) can be reduced with high energy virtual monoenergetic images (VMI) and iterative metal artifact reduction (IMAR) algorithms. At high VMI energies, however, iodinated contrast media show decreased attenuation. High atomic number (high-Z) contrast media potentially preserve vessel contrast near metal implants even at high VMI energies. Hence, the purpose of this study was to assess the effect of high-Z contrast media on vessel visualization near metal implants in photon-counting detector (PCD)-CT across VMI energies, with and without IMAR and for different metal types. Methods: A pelvis phantom containing titanium or steel inserts and contrast media inserts including iodine, bismuth, holmium, or tungsten was scanned using photon-counting detector computed tomography (PCD-CT). VMI (40-190 keV, 1 keV steps) were reconstructed with and without IMAR. Three predefined regions of interest (ROI) were placed in the background (background noise, standard deviation of HU), in the contrast media inserts (vessel attenuation, mean HU), and between the metal and contrast inserts (metal artifacts, defined as standard deviation of HU). An artifact-adjusted contrast-to-noise ratio (CNR) was calculated using background noise, vessel attenuation and metal artifacts, and averaged across three VMI energy ranges: 40-90, 90-140, and 140-190 keV. Peak CNR was the maximum value across all VMI energies. Wilcoxon rank sum tests with Benjamini-Hochberg correction were applied. Results: Metal artifacts decreased with increasing VMI energy (P<0.001). Titanium caused fewer artifacts than steel, and IMAR further reduced artifacts from both metal types: at 40-90 keV without IMAR, metal artifacts averaged over all contrast media were 71 Hounsfield units (HU) (titanium) vs. 116 HU (steel), decreasing to 27 and 32 HU with IMAR (P<0.001). At 40-90 keV in titanium with IMAR, holmium showed the highest vessel attenuation and CNR (451 HU/24), followed by iodine (296 HU/15), bismuth (267 HU/14) and tungsten (259 HU/13). At 140-190 keV, tungsten showed the highest vessel attenuation and CNR (269 HU/19), followed by bismuth (250 HU/17), holmium (144 HU/10) and iodine (31 HU/2). Peak CNR [34] was achieved with holmium, titanium, IMAR, and VMI at 40 keV. Conclusions: High-Z contrast media provide superior vessel contrast compared to iodine near metal implants in PCD-CT, both at low VMI energy with holmium and at high VMI energy with tungsten and bismuth, where metal artifacts are additionally reduced. Under metal artifact conditions, vessel contrast can be further improved by applying IMAR.

Purpose To determine whether baseline clinical characteristics and cardiac MRI parameters predict major adverse cardiac events (MACEs) in participants with angiographically confirmed spontaneous coronary artery dissection (SCAD). Materials and Methods This prospective single-center study included participants with SCAD who were angiographically diagnosed between March 2018 and November 2023. Cardiac MRI was performed after a median of 4 days (IQR, 1.5-7) from symptom onset. SCAD types were classified according to the Yip-Saw system. Follow-up evaluation was performed at a median of 5.5 months after discharge, and MACEs were recorded. The primary outcome was the occurrence of MACEs. Secondary analyses included extent of late gadolinium enhancement (LGE). Statistical analysis included binary logistic and Cox proportional hazards regression. Results Overall, 59 participants (mean age, 49 years ± 10; 40 female participants [68%]) were included. ST-elevation myocardial infarction at presentation was diagnosed in 24 of 59 (41%). Angiographically, 41 of 59 (69.5%) were SCAD type 2. Baseline cardiac MRI demonstrated acute injury in 48 of 59 (81%) and LGE in 54 of 59 (93%), typically moderate (median, three segments [IQR, two to five]). In the adjusted model, ST-elevation myocardial infarction manifestation independently predicted greater LGE extent (P = .02; odds ratio, 7.00; 95% CI: 2.00, 24.00). After multivariable adjustment, SCAD type 1 was significantly associated with MACEs (P = .002; hazard ratio, 10.00; 95% CI: 2.00, 23.00), as was transmural LGE (P = .006; hazard ratio, 1.50; 95% CI: 1.10, 2.10). A threshold of greater than or equal to four LGE segments identified a critical risk zone. Conclusion In SCAD, SCAD type 1 and involvement of more than three transmural LGE segments at acute cardiac MRI independently predicted MACEs. Keywords: MR Perfusion, Cardiac, Arteries, Cardiomyopathies, Ischemia/Infarction Supplemental material is available for this article. © RSNA, 2026.

BACKGROUND:Previous research has highlighted the benefits of reducing contrast media (CM), demonstrating positive impacts on patient safety, environmental sustainability, and health care costs. The 10-to-10 rule, introduced by a single-center study, adjusts CM dose to total body weight and tube voltage. This approach resulted in a reduced overall CM volume, with homogeneous attenuation and consistent diagnostic image quality (IQ) across varying tube voltages. OBJECTIVES:This study aimed to evaluate the effectiveness of the 10-to-10 rule in achieving consistent and homogeneous attenuation in vascular and parenchymal CT in a multicenter clinical practice setting across Europe. MATERIALS AND METHODS:A total of 1,037 patients scheduled for CT of the coronary arteries (high-pitch and sequential CCTA), pulmonary arteries (CTPA), aorta (CTA aorta), and abdominal CT in portal venous phase or venous phase scans of the neck were included in this nonrandomized multicenter trial, conducted at 5 centers in the Netherlands, Germany, and Switzerland. Each center followed its standard scan and reconstruction protocol based on the clinical request. CM protocols were based on the 10-to-10 rule: A 10 kV reduction in tube voltage should be accompanied by a 10% decrease in iodine delivery rate for vascular studies or total iodine load in parenchymal studies, and vice versa. Objective image quality (IQ) was assessed by drawing region of interests, measuring attenuation [Hounsfield Unit (HU)], and calculating signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). In vascular studies, a reference line was included, representing the threshold for sufficient diagnostic IQ (CCTA-325 HU, CTPA-200 HU, and CTA Aorta-250 HU). 95% CI of the mean attenuation was calculated, and the lower bound of each 95% CI was used as the reference to assess whether attenuation met these thresholds. Generalized mixed models tested for significant differences in objective IQ across varying tube voltages, presented both unadjusted and multivariate adjusted by age and gender. RESULTS:Results demonstrated no significant differences in attenuation for distal high-pitch CCTA, proximal sequential CCTA, distal CTPA, CTA aorta, abdominal portal venous phase scans, and the thyroid gland and sternocleidomastoid muscle in venous phase scans of the neck after adjusting for age and gender. Proximal high-pitch CCTA, distal sequential CCTA, and proximal CTPA yielded significant results ( P =0.030, P <0.001, and P =0.002, respectively). SNR and CNR showed no significant differences for all scan protocols. The majority of 95% CI lower bounds exceeded the predefined threshold for sufficient diagnostic IQ. Exceptions included high-pitch CCTA scans, where only the 90 kV level met the threshold, as well as in sequential CCTA at 120 kV, and CTPA at 110 and 120 kV, for which the lower bounds remained below the threshold. CONCLUSIONS:This study demonstrates the generalizability and effectiveness of the 10-to-10 rule in a multicenter trial setting and a large patient population, showing limited significant deviations in iodine attenuation across varying tube voltages for both vascular and parenchymal CT studies.

To assess the diagnostic performance of photon-counting detector computed tomography (PCD-CT) and cone-beam computed tomography (CBCT) at dose-matched radiation levels (high, standard, and low) for detecting and evaluating simulated endodontic conditions, treatments, and associated complications. Sixteen extracted third molars with eight endodontic tasks were imaged using PCD-CT and CBCT. Qualitative (image quality, artifact susceptibility, diagnostic interpretability) and quantitative (endodontic working length) parameters were assessed by two observers using a five-point Likert scale. Descriptive statistics and weighted kappa (κ) were used for data analysis. High- and standard-dose PCD-CT demonstrated superior image quality and anatomical visualization compared to CBCT (median 5, IQR 5–5; κ = 1.0; all p < 0.001). Low-dose PCD-CT remained diagnostically robust, outperforming CBCT, except in root canal visualization, where both performed similarly. Diagnostic accuracy of pathologies and complications was slightly higher with PCD-CT (80–88