Siemens (France)

Cardiac graft rejection and allograft vasculopathy (CAV) are major causes of morbidity and mortality in heart transplant (HT) patients. While endomyocardial biopsy and invasive coronary angiography remain diagnostic gold standards, their invasiveness highlights the need for safer, noninvasive alternatives. Cardiac computed tomography (CT) has emerged as a promising modality for evaluating both coronary and myocardial status. The primary aim of this study is to evaluate CT-measured extracellular volume (ECVCT) in HT patients compared to a control group and identify its clinical determinants. The secondary objective is to explore the association between ECVCT and CAV severity. In a reference HT center, we conducted a retrospective cohort study of 163 patients comprising 80 HT patients and 83 age- and sex-matched controls without structural heart disease studied with a standardized CT protocol. Twenty-two control patients had concomitant cardiac CT and magnetic resonance (CMR) to validate ECVCT measurements. Determinants of ECVCT including rejection history, CAD-RADS, CAV and cardiovascular risk factors were studied. Median ECVCT was significantly higher in HT patients (34%, IQR 30-38) compared to controls (29%, IQR 27-31; p<0.001). ECVCT was highly correlated with MR-ECV (r=0.88, p<0.001). In HT recipients, elevated ECVCT was independently associated to hypertension , smoking, presence of CAV, elevated CAD-RADS scores and a history of graft rejection, whereas in controls only higher coronary artery calcium scores correlated with increased ECVCT. CONCLUSION: ECVCT is increased in HT patients compared to controls and associated with rejection history and CAV. ECVCT emerges as a promising noninvasive tool for the simultaneous assessment of myocardial alterations and CAV in HT patients showing strong concordance with CMR and high reproducibility. Further multicenter studies are warranted to confirm its role in transplant surveillance protocols.

This article reports the results of the second iteration of the autoPET challenge on automated lesion segmentation in whole-body PET/CT, held in conjunction with the 26th International Conference on Medical Image Computing and Computer Assisted Intervention in 2023. In contrast to the first autoPET challenge, which served as a proof of concept, this study investigates whether machine learning-based segmentation models trained on data from a single source can maintain performance across clinically relevant variations in PET/CT data, reflecting the demands of real-world deployment. Methods: A comprehensive biomedical segmentation challenge on PET/CT domain generalization was designed and conducted. Participants were tasked to train machine learning models on annotated whole-body 18F-FDG data (n = 1,014). These models were then evaluated on a test set of 200 samples from 5 clinically relevant domains, including variations in institutions, pathologies, and populations and a different tracer. Performance was measured in terms of average dice similarity coefficient, average false-positive volume, and average false-negative volume. The best-performing teams were awarded in 3 categories. Furthermore, a detailed analysis was conducted after the challenge, examining results across domains and unique instances, along with a ranking analysis. Results: Generalization from a single-source domain remains a significant challenge. Seventeen international teams successfully participated in the challenge. The best-performing team reached an average dice similarity coefficient of 0.5038, a mean false-positive volume of 87.8388 mL, and a mean false-negative volume of 8.4154 mL on the test set. nnU-Net was the most commonly used framework, with most participants using a 3-dimensional U-Net. Despite competitive in-domain results, out-of-domain performance deteriorated substantially, particularly on pediatric and prostate-specific membrane antigen data. Detailed error analysis revealed frequent false-positives due to physiologic uptake and decreased sensitivity in detecting small or low-uptake lesions. A majority-vote ensemble offered minimal performance gains, whereas an oracle ensemble indicates hypothetical gains. Ranking analysis showed no single team consistently outperformed all others across ranking schemes. Conclusion: The second autoPET challenge provides a comprehensive evaluation of the current state of automated PET/CT tumor segmentation, highlighting both progress and persistent challenges of single-source domain generalization and the need for diverse public datasets to enhance algorithm robustness.

The purpose of this study was to evaluate the diagnostic capability of mineralized tissue-magnetic resonance imaging (MT-MRI) to detect erosions, sclerosis, and ankylosis of the sacroiliac joint (SIJ) in patients with axial spondyloarthritis, by comparison with T1-weighted MRI and pelvic computed tomography (CT), using SIJ CT as the standard of reference. This retrospective study included 100 patients (62 women, 38 men; mean age, 39.9 ± 14.3 [standard deviation] years; age range: 19-79) with suspected axial spondyloarthritis, who underwent SIJ MRI and CT on the same day between August 2023 and March 2025. Two musculoskeletal radiologists independently scored the amount of structural lesions of SIJs. The diagnostic confidence in each imaging modality was also evaluated. The erosion scores showed no significant difference between SIJ CT and MT-MRI for both readers (P ≥ 0.07) but were lower than those of SIJ CT when using T1-weighted MRI for both readers (P ≤ 0.011). The performance of pelvic CT for depicting erosion was intermediate but closer to that of MT-MRI. The sclerosis scores were 16-20 % lower with T1-weighted MRI than with SIJ CT (P ≤ 0.012) and 3 % lower with MT-MRI (P ≤ 0.04), but 8 % overestimated using pelvic CT (P ≤ 0.001). For both groups, SIJ CT obtained the highest confidence score, which was superior to pelvic CT (P ≤ 0.001), itself superior to T1-weighted MRI and MT-MRI (P ≤ 0.001), with the latter two not differing significantly (P ≥ 0.109). T1-weighted MRI alone is insufficient for reliably evaluating structural lesions of SIJs due to sacroiliitis in patients with axial spondyloarthritis. MT-MRI emerges as the closest alternative to SIJ CT, demonstrating excellent diagnostic performance while eliminating radiation exposure.

ABSTRACTNeuromelanin (NM) magnetic resonance imaging has been used to evaluate the loss of melanized neurons in the substantia nigra, the main characteristic of Parkinson disease, typically by measuring the contrast ratio (CR) between the NM‐rich areas and the cerebral peduncles in the midbrain. Neuromelanin contrast can be generated by employing a 3D gradient‐echo (GRE) sequence with magnetization transfer (MT). In this work, we first evaluated the effect of the MT pulse frequency on the CR and contrast‐to‐noise ratio (CNR), analyzing a large frequency range from 500 to 100K Hz. Secondly, the impact of the 3D GRE sequence flip angle (FA) was evaluated using angles from 5° to 40°. Additionally, images were acquired both with and without MT for each FA, providing an opportunity to examine the effect of MT on tissue proton density, T1, and T2* values. Results showed that the highest CR and CNR were obtained for the lower MT frequencies (500–2000 Hz) and lower FAs (5°–10°). The lower FAs improved the visualization of the neuromelanin‐rich area in the substantia nigra and facilitated delineating its volume. In addition, this work showed that the MT pulse decreased the T1 and PD of the tissue. Furthermore, simulations supported the obtained in vivo results.

Motion-induced shot-to-shot phase variation and strong image aliasing artifacts are common in diffusion weighted imaging (DWI) multi-shot EPI (MS-EPI). Herein, motion-compensated diffusion encoding waveforms were used to minimize shot-to-shot phase variation, and an MS-EPI with Keyhole (MS-EPIK) trajectory was evaluated to mitigate image aliasing. MS-EPI and MS-EPIK with non-motion compensated (M0), first order (M0M1), and first & second order (M0M1M2) motion-compensated diffusion encoding waveforms and a reference single-shot (SS-EPI) acquisition with M0 diffusion encoding were acquired invivo at 3T in five volunteers in the brain, liver, and heart. Mean diffusivity (MD) and fraction of anisotropy (FA) were reported in the brain and heart, and the apparent diffusion coefficient (ADC) in the liver. No statistical differences in MD and FA between the SS-EPI, MS-EPIK, and MS-EPI when using the M0M1M2 waveform were found in white and gray matter. In the right liver lobe, statistical differences were found between the ADC of the SS-EPI and MS-EPIK using the M0, M0M1, and M0M1M2 waveforms (p < 0.001) and with MS-EPI using M0M1M2 (p < 0.001). No differences were observed in MD and FA in the heart between SS-EPI, MS-EPI, and MS-EPIK in the heart. MS-EPIK is less sensitive to image aliasing than MS-EPI approach but remains susceptible to image distortion. Overall, M0M1M2 waveforms were found to be the best approach to mitigate shot-to-shot phase variation for MS-EPI in the brain, liver, and heart.

To evaluate the performance of CT-like MRI sequences (gradient echo with radial k-space filling (GRE), pointwise encoding time reduction with radial acquisition (PETRA), radial Ultrashort Echo Time (UTE)) versus ultra-high-resolution CT (UHR-CT) in assessing carpal bones and soft tissue calcifications in cadaveric wrists. Five anonymized cadaveric forearm specimens were imaged using a 3T MRI system with GRE, PETRA, and radial UTE sequences, alongside UHR-CT. Evaluated parameters included bone contours, carpal bone dimensions, cortical thickness, lesion size and soft tissue calcifications. Detection and diagnostic confidence of soft tissue calcifications were graded, and Contrast-to-Noise Ratio (CNR) was assessed for various tissues. GRE provided the clearest bone contour visualization, closely matching UHR-CT, with a mean difference of less than 1mm (p=0.9). Geode sizes were underestimated by 16.1% on GRE, 15.6% on PETRA, and 22.5% on radial UTE. GRE showed the highest CNR for bone (33.6±15.4), outperforming PETRA (15.8±8.5) and radial UTE (11.4±8.1). Cortical thickness was overestimated significantly by PETRA (p=0.05) and radial UTE (p=0.009), but not by GRE (p=0.5). GRE detected the most calcifications, but over 75% of hypodense calcifications remained undetected. Overall, GRE offered the best bone contour visualization and CNR, while PETRA and radial UTE were better at distinguishing calcified tissue from tendons. CT-like MRI sequences accurately assess bone morphology, with GRE offering the best bone contour visualization and CNR.

Fasting shows promise for public health, but concerns about muscle loss hinder its acceptance, particularly among the elderly. We explored the impact of long-term fasting (12 days, 250 kcal/day) on muscle structure, metabolism and performance. We prospectively assessed muscle volume, composition, relaxometry data and lipid metabolism in 32 subjects (16 men; 50% over 50 years old) before fasting, at the end of fasting and 1 month post-fasting. Techniques included high-resolution 3D Dixon MR imaging, multiecho CSE and single-voxel MR spectroscopy. Dynamic 31P-MRS, quantitative MRI, maximal voluntary contraction (MVC) measurements and exercise testing (VO2peak) were repeated throughout the protocol. Although the average body weight loss was 5.9 kg (7.4%, p < 0.001), the skeletal muscle volume change measured on the right calf muscle was 271 mL (5.4%, p < 0.001). This closely aligns with expected losses of glycogen (1%-2%) and bound water (3%-4%), estimated to total 404-505 mL. MVC (anaerobic lactic metabolism) remained preserved in both thighs and calf muscles, regardless of sex or age. Unchanged T2 showed that fasting did not induce structural or inflammatory changes. MRI/MRS revealed fat redistribution among tissues, with subcutaneous fat decrease (by 417.2 cm3, p < 0.01) and total fat fraction increase (by 0.2%, p < 0.05) in muscle. The intramyocellular lipid pool increased by 2.2 times (p < 0.05), whereas the extracellular lipid pool decreased to 1.4 times (p < 0.05), revealing rapid lipid trafficking and adaptation. During fasting, the T2* value increased by 1.2 ms (p < 0.001), likely because of changes in the configuration of intracellular lipid droplets, with an increased proportion of lipid droplets of smaller size, optimizing accessibility of lipid fuels and mitochondrial FA. Exercise testing (VO2peak) showed no change in maximal oxygen uptake, but fat oxidation improved with a 10% decrease in the exercise respiratory exchange ratio (p < 0.001). Mitochondrial oxidative capacity and PCr resynthesis rates in muscle were maintained. Females improved their mitochondrial function by D + 12, with τPCr decreasing to 29.61 s (p < 0.01), surpassing males and demonstrating better fat oxidation capabilities. Long-term fasting did not alter muscle metabolism or performance, nor induced structural or inflammatory changes. The decrease in muscle volume is minor when accounting for glycogen and water depletion during fasting. Fat is relocated to the intracellular compartment of myocytes. Both anaerobic and aerobic metabolic pathways remain unchanged after 12 days of fasting in both sexes and older subjects. This suggests that human muscles, like those in animals, have evolved to withstand seasonal food shortages and endure long fasting periods.

7T MRI imaging of the pituitary gland is an emerging technique. The purpose of this article is to review the current status of the 7T MRI of the pituitary gland, particularly in the context of pituitary microadenoma pathology. We will discuss technical challenges and parallel transmission opportunities. Follow-up study selection and data extraction were performed following PRISMA guidelines. We focused on diagnostic performance and acquisition protocols. Inclusion criteria were: MRI imaging studies of pituitary adenoma at 7T. Exclusion criteria were: Case reports and reviews; studies which did not report MRI protocols; surgical planning studies; studies focusing exclusively on macroadenomas for which ultra-high magnetic field imaging is less decisive than microadenomas in clinical practice. Six studies were included. 7T MRI outperformed 1.5 or 3T MRI for the detection of microadenomas. Acquisition protocols employed were heterogeneous, with two-dimensional T2-w and T1-w turbo spin-echo sequences, three-dimensional T1-w isotropic spin-echo and gradient-echo sequences (resolution: 0.6 and 0.8mm), and dynamic contrast-enhanced T1-w sequences. 7T MRI is a promising tool for overcoming the difficulties encountered by conventional MRI, particularly in the case of Cushing disease. However, there is insufficient data to precisely define an optimal protocol yet.

To determine whether plaque composition analysis defined by cardiac CT can provide incremental prognostic value above coronary artery disease (CAD) burden markers in symptomatic patients with obstructive CAD. Between 2009 and 2019, a multicentric registry included all consecutive symptomatic patients with obstructive CAD (at least one ≥ 50% stenosis on CCTA) and was followed for major adverse cardiovascular (MACE) defined by cardiovascular death or nonfatal myocardial infarction. Each coronary segment was scored visually for both the degree of stenosis and composition of plaque, which were classified as non-calcified, mixed, or calcified. To assess the prognostic value of each CCTA findings, different multivariable Cox regression models were used: model 1: clinical (traditional risk factors); model 2: model 1 + CAD burden (number of proximal segments with stenosis ≥ 50% + number of vessels with obstructive CAD); and model 3: model 2 + plaques feature (number of segments with non-calcified plaque). Of 2312 patients (mean age 70 ± 12 years, 46% men), 319 experienced a MACE (13.8%) (median follow-up: 6.7 years (5.9-9.1)). The number of proximal segments with ≥ 50% stenosis, the number of vessels with obstructive CAD, and the number of segments with non-calcified plaque were all independently associated with MACEs (all p < 0.001). The addition of plaque composition analysis (model 3) showed the best improvement in model discrimination and reclassification (C-statistic improvement = 0.03; net reclassification improvement = 28.6%; integrative discrimination index = 5.4%, all p < 0.001). In this population, the analysis of coronary plaque composition had an incremental prognostic value to predict MACEs above a model combining traditional risk factors and CAD burden. Question Several coronary computed tomography angiography (CCTA) studies have shown the potential interest of plaque composition analysis, which can be further evaluated. Findings In symptomatic patients with obstructive coronary artery disease (CAD), plaque composition analysis had an incremental prognostic value above a model combining traditional risk factors and CAD burden. Clinical relevance In symptomatic patients with obstructive CAD, plaque composition analysis using CCTA has a strong incremental prognostic value above a model combining traditional risk factors and CAD burden, thus translating into a more accurate long-term major adverse cardiovascular event prediction.

BackgroundWe evaluated the accuracy of magnetic resonance imaging (MRI) computed tomography (CT)-like sequences compared to normal-resolution CT (NR-CT) and super-high-resolution CT (SHR-CT) for planning of cochlear implantation.MethodsSix cadaveric temporal bone specimens were used. 3-T MRI scans were performed using radial volumetric interpolated breath-hold (STARVIBE), pointwise-encoding time reduction with radial acquisition (PETRA), and ultrashort time of echo (UTE) sequences. CT scans were performed on two scanners for SHR-CT and NR-CT acquisitions. Two radiologists evaluated accuracy based on preimplantation metrics and the ability to identify various anatomical structures, particularly the facial recess and round window. Wilcoxon rank-sum test and intraclass correlation coefficient (ICC) were used.ResultsThe facial nerve was always clearly visible (score ≥ 2) in the MRI, NR-CT, and SHR-CT scans (p ≥ 0.621). However, the chorda tympani nerve (CTN) was clearly visualized in UTE, STARVIBE, and PETRA sequences in only 33% (2/6 specimens, p = 0.016), 50% (3/6 specimens, p = 0.038), and 83% (5/6 specimens, p = 0.017) of cases, respectively, whereas it was always clearly visualized in SHR and NR-CT (p = 0.426). The round window (RW) was never visualized in MRI sequences (p ≤ 0.010), whereas it was identified in all cases in SHR and NR-CT (p = 1.000). There was a strong correlation between measurements obtained from MRI and CT modalities (ICC ≥ 0.837).ConclusionMRI CT-like sequences assessed the facial nerve in all cases and the CTN in up to 87% of cases. However, the detection of the RW was insufficient for surgical planning. CT and MRI measurements were in agreement.Relevance statementCT-like MRI sequences can image the anatomy of the facial recess and the length of the basal turn of the cochlea with similar accuracy as conventional CT, although they cannot image the round window.Key PointsCT-like MRI sequences are not widely used in preoperative cochlear implantation imaging.CT-like sequences can image the facial recess as well as conventional CT.CT-like sequences can image the basal turn length of the cochlea as well as conventional CT.Round window depiction is not possible with CT-like MRI sequences.Graphical