Background: In multiple sclerosis (MS), mitochondrial dysfunction contributes to disease progression and may impair cognitive function, particularly in vulnerable regions such as the hippocampus. Gadolinium-based contrast agents (GBCAs) are widely used for imaging-based diagnosis of MS; however, evidence indicates that gadolinium (Gd) can be released from low-stability agents and retained in the brain. Whether retained Gd affects neuronal mitochondria, particularly under inflammatory conditions, remains unclear. We investigated hippocampal Gd retention following in vivo GBCA exposure and assessed associated mitochondrial effects in hippocampal slice cultures. Methods: Mice with experimental autoimmune encephalomyelitis (EAE) and healthy controls received repeated injections of linear gadopentetate-dimeglumine (gadopentetate) or macrocyclic gadobutrol (cumulative dose: 20 mmol/kg body weight). Hippocampal Gd distribution and retention kinetics were analyzed 1, 10, and 40 days post-final injection (p.f.i.) using laser ablation inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-ToF-MS). Ex vivo, organotypic hippocampal slice cultures from B6.Cg-Tg(Thy1-CFP/COX8A)S2Lich/J mice expressing fluorescently labeled neuronal mitochondria were exposed to TNF-alpha (paradigm of inflammation)±gadopentetate or gadobutrol for 48 hours (0.1, 1, 10, 50 mM). Mitochondrial dynamics were quantified using semi-automated and manual analyses of confocal microscopy images, and Gd slice content was determined by ICP-MS. Results: In vivo, neuroinflammation increased hippocampal Gd accumulation following administration of both GBCAs in EAE mice. However, long-term retention up to 40 days p.f.i. was observed exclusively for gadopentetate, particularly in EAE mice. Ex vivo, prolonged exposure to both GBCAs at low-to-intermediate concentrations (0.1 to 10 mM) reduced mitochondrial length and area, particularly under inflammatory conditions, and altered mitochondrial motility relative to untreated controls. At these concentrations, intratissue Gd levels, quantified by ICP-MS under representative conditions, were within a biologically relevant, sub-cytotoxic range. Marked motility impairment and mitochondrial rounding occurred only at the highest gadopentetate concentration (50 mM). Interestingly, although inflammation did not alter Gd concentrations within the ex vivo slices, mitochondrial alterations were more pronounced under inflammatory conditions. Conclusion: In the hippocampus, long-term Gd retention in vivo appears to be restricted to linear GBCAs, whereas ex vivo, exposure to both linear and macrocyclic GBCAs at biologically relevant concentrations alters neuronal mitochondrial morphology and dynamics. Inflammation further amplifies these effects, highlighting the importance of considering GBCA-associated mitochondrial damage when evaluating their potential neurotoxic risks, particularly in neuroinflammatory diseases.
Objective: Motion artifacts remain a limitation of cardiac CT when assessing both native and prosthetic heart valves, particularly during phases of rapid motion. This may lead to reduced image quality, potentially impairing the evaluation of valvular movement and pathology. The purpose of this study was to evaluate whether a novel reconstruction-based motion correction algorithm improves image quality and reduces motion artifacts of native and prosthetic heart valves compared with standard reconstructions in photon-counting detector CT (PCD-CT). Materials and Methods: In this retrospective single-center study, 57 patients [21 women; median age, 71 (interquartile range, 57 to 78 y)] who underwent clinically indicated 4D cardiac CT for suspected native and prosthetic valvular disease were included. Images were acquired using retrospectively electrocardiography (ECG)-gated spiral dual-source PCD-CT without ECG-pulsing. Images were reconstructed in 10% steps throughout the RR-interval using both standard (TrueStack) and an otherwise identical reconstruction using the novel motion correction algorithm (ZeeFreePlus). Subjective image quality and motion artifacts were independently assessed by 2 blinded, experienced readers using a 4-point visual analog scale for 3 categories: valve frame/annulus, valve leaflets, and valvular pathology. Objective analysis included quantification of the volume of artifacts throughout the cardiac cycle. Results: A total of 68 valves were evaluated, including 57 prosthetic valves (22 transcatheter aortic valve replacements and 19 surgical valves, 11 mitral valves, and 5 tricuspid valve interventions) and 11 native valves. Valvular pathology was present in 29 cases, with the most prevalent being hypoattenuated leaflet thickening in 14/29 (48%). Motion-corrected reconstructions significantly improved image quality and reduced motion artifacts across all cardiac phases and all categories (all, P <0.001). The largest improvements were observed during systole, particularly at 10% of the RR-interval, with significantly greater gains than during diastole ( P <0.05). Improvements were consistent across aortic and atrioventricular prosthetic valves and translated into improved visualization of valvular pathology ( P <0.001). Objective quantitative analysis corroborated the subjective image quality findings by demonstrating reductions in the volumes of motion-induced artifacts when using the algorithm ( P <0.001). Conclusions: A novel motion correction algorithm substantially reduced motion artifacts and improved image quality in both native and prosthetic heart valve imaging with PCD-CT, with the largest improvements in systole. These benefits resulted in enhanced visualization of valvular pathology, potentially reinforcing the growing clinical role of cardiac CT for the assessment of valve disease.
Background: Stress perfusion cardiac magnetic resonance imaging (MRI) enables accurate detection of myocardial ischemia. While contrast injection parameters, particularly iodine delivery rate, are known to influence image quality in CT, their impact in cardiac MRI remains insufficiently studied. This study aimed to evaluate the effect of different gadolinium-based contrast agent (GBCA) injection rates on objective and subjective image quality in perfusion cardiac MRI in patients with suspected ischemic heart disease. Methods: Ninety patients scheduled for a stress perfusion cardiac MRI were retrospectively included and allocated to 3 groups based on the GBCA injection rate used (eg, group 1: 6 mL/s, group 2: 4 mL/s, and group 3: 2 mL/s). Blood-pool signal intensity was extracted on a frame-by-frame basis to generate signal-intensity time curves. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for all relevant regions, including SNR ischemia , SNR blood , SNR myocardium , CNR ischemia–blood , CNR myocardium–blood , and CNR ischemia–myocardium . Subjective image quality was scored on a 5-point Likert scale, blindly assessed in consensus by 2 cardiovascular radiologists. Results: Blood-pool peak intensity was the highest in the group with flow rates of 6 mL/s. Peak signal intensity was for the 6, 4, and 2 mL/s group, respectively, 17525±3616, 15213±3416, and 15534±2990 a.u. ( P =0.019) and post hoc comparison demonstrated a significant difference between the 6 mL/s and 4 mL/s group ( P =0.027). No significant differences in signal intensity of the myocardium, blood pool and the infarcted region were found between groups ( P =0.475, 0.399 and 0.519, respectively). Image noise was significantly higher in group 1 compared to group 3 ( P value=0.036). SNR of myocardium, blood, and ischemia was not significantly different between groups ( P =0.525, 0.595, and 0.453, respectively). CNR for ischemia-blood, myocardium-blood and ischemia-myocardium were the highest in group 3, but not significantly different ( P =0.373, 0.896, and 0.346, respectively). Subjective image quality and reader confidence were not significantly different between groups ( P values of 0.985 and 0.842). Although contrast quality demonstrated a statistically significant difference across groups ( P =0.026), this finding was not considered clinically relevant. Conclusion: Higher GBCA injection rates resulted in higher blood-pool peak enhancement, yet did not translate into significant differences in objective image and subjective image quality. Lower injection rates appear sufficient to achieve adequate myocardial perfusion imaging, suggesting a plateau in image quality in which increasing flow rates do not show added benefit.
BACKGROUND:Single-shot echo-planar imaging DWI (ss-EPI DWI) is susceptible to geometric distortions near air-tissue interfaces, limiting diagnostic accuracy. Multishot readout-segmented DWI (RESOLVE DWI) mitigates these artifacts but requires longer acquisition times. This study evaluated whether ss-EPI DWI with a deep learning-enabled correction of static field inhomogeneities (DL DWI) can achieve effective distortion correction while preserving diagnostic reliability and reducing scan time. OBJECTIVES:To compare image quality, geometric distortion, lesion detectability, and diagnostic confidence of ss-EPI DWI with DL-enabled correction of static field inhomogeneities (DL DWI) against conventional ss-EPI DWI (without correction) and RESOLVE DWI. MATERIALS AND METHODS:In this prospective single-center study (April 2025 to August 2025), 100 patients undergoing clinically indicated brain MRI were enrolled following written informed consent. All patients underwent DL ss-EPI DWI with DL correction (1 min 29 s) and RESOLVE DWI (3 min 17 s); ss-EPI DWI was reconstructed by disabling DL correction for all patients. Qualitative and quantitative analyses were performed. Three board-certified radiologists rated image quality, lesion detectability, distortion, and diagnostic confidence on a 5-point Likert Scale. Two quantitative measures of distortion were applied: geometric conformity with anatomic 3D T1-weighted data through coregistration methods and gray-value distributions within volumes of interest in susceptibility-affected regions (temporal lobe, cerebellum, and brainstem). RESULTS:DL DWI significantly outperformed ss-EPI DWI across all qualitative parameters, including diagnostic confidence (median, 4.0 vs. 3.0; P < 0.001), overall image quality (median, 4.0 vs. 3.0; P < 0.001), and geometric distortion (median, 4.0 vs. 3.0; P < 0.001). RESOLVE DWI achieved the highest ratings overall (median, 5.0). Lesion detectability was comparable between DL DWI and RESOLVE DWI (median, 4.0 for both; P > 0.08), while both significantly outperformed ss-EPI DWI (P < 0.001). Quantitative analysis confirmed superior geometric accuracy of DL DWI over ss-EPI DWI, with lower coregistration cost-function values and normalization of gray-value distributions in susceptibility-affected regions. CONCLUSION:DL DWI improved image quality and geometric accuracy compared with uncorrected ss-EPI DWI. Subjective lesion-detectability ratings were similar between DL DWI and RESOLVE DWI, while DL DWI required less than half the acquisition time. These findings support DL-based distortion correction as a promising, time-efficient approach for brain diffusion-weighted imaging that warrants confirmation in a predefined noninferiority design.
Background: Single-shot echo-planar imaging DWI (ss-EPI DWI) is susceptible to geometric distortions near air–tissue interfaces, limiting diagnostic accuracy. Multishot readout-segmented DWI (RESOLVE DWI) mitigates these artifacts but requires longer acquisition times. This study evaluated whether ss-EPI DWI with a deep learning–enabled correction of static field inhomogeneities (DL DWI) can achieve effective distortion correction while preserving diagnostic reliability and reducing scan time. Objectives: To compare image quality, geometric distortion, lesion detectability, and diagnostic confidence of ss-EPI DWI with DL-enabled correction of static field inhomogeneities (DL DWI) against conventional ss-EPI DWI (without correction) and RESOLVE DWI. Materials and Methods: In this prospective single-center study (April 2025 to August 2025), 100 patients undergoing clinically indicated brain MRI were enrolled following written informed consent. All patients underwent DL ss-EPI DWI with DL correction (1 min 29 s) and RESOLVE DWI (3 min 17 s); ss-EPI DWI was reconstructed by disabling DL correction for all patients. Qualitative and quantitative analyses were performed. Three board-certified radiologists rated image quality, lesion detectability, distortion, and diagnostic confidence on a 5-point Likert Scale. Two quantitative measures of distortion were applied: geometric conformity with anatomic 3D T1-weighted data through coregistration methods and gray-value distributions within volumes of interest in susceptibility-affected regions (temporal lobe, cerebellum, and brainstem). Results: DL DWI significantly outperformed ss-EPI DWI across all qualitative parameters, including diagnostic confidence (median, 4.0 vs. 3.0; P < 0.001), overall image quality (median, 4.0 vs. 3.0; P < 0.001), and geometric distortion (median, 4.0 vs. 3.0; P < 0.001). RESOLVE DWI achieved the highest ratings overall (median, 5.0). Lesion detectability was comparable between DL DWI and RESOLVE DWI (median, 4.0 for both; P > 0.08), while both significantly outperformed ss-EPI DWI ( P < 0.001). Quantitative analysis confirmed superior geometric accuracy of DL DWI over ss-EPI DWI, with lower coregistration cost-function values and normalization of gray-value distributions in susceptibility-affected regions. Conclusion: DL DWI improved image quality and geometric accuracy compared with uncorrected ss-EPI DWI. Subjective lesion-detectability ratings were similar between DL DWI and RESOLVE DWI, while DL DWI required less than half the acquisition time. These findings support DL-based distortion correction as a promising, time-efficient approach for brain diffusion-weighted imaging that warrants confirmation in a predefined noninferiority design.
