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Background: Abdominal aortic aneurysms (AAAs) may rupture before reaching maximum diameter (Dmax) thresholds for repair. Aortic wall microvasculature has been associated with elastin content and rupture sites in specimens, but its relation to progression is unknown. Purpose: To investigate whether dynamic contrast‐enhanced (DCE) MRI of AAA is associated with Dmax or growth. Study Type: Prospective. Population: A total of 27 male patients with infrarenal AAA (mean age ± standard deviation = 75 ± 5 years) under surveillance with DCE MRI and 2 years of prior follow‐up intervals with computed tomography (CT) or MRI. Field Strength/Sequence: A 3‐T, dynamic three‐dimensional (3D) fast gradient‐echo stack‐of‐stars volumetric interpolated breath‐hold examination (Star‐VIBE). Assessment: Wall voxels were manually segmented in two consecutive slices at the level of Dmax. We measured slope to 1‐minute and area under the curve (AUC) to 1 minute and 4 minutes of the signal intensity change postcontrast relative to that precontrast arrival, and, Ktrans, a measure of microvascular permeability, using the Patlak model. These were averaged over all wall voxels for association to Dmax and growth rate, and, over left/right and anterior/posterior quadrants for testing circumferential homogeneity. Dmax was measured orthogonal to the aortic centerline and growth rate was calculated by linear fit of Dmax measurements. Statistical Tests: Pearson correlation and linear mixed effects models. A P value <0.05 was considered statistically significant. Results: In 44 DCE MRIs, mean Dmax was 45 ± 7 mm and growth rate in 1.5 ± 0.4 years of prior follow‐up was 1.7 ± 1.2 mm per year. DCE measurements correlated with each other (Pearson r = 0.39–0.99) and significantly differed between anterior/posterior versus left/right quadrants. DCE measurements were not significantly associated with Dmax (P = 0.084, 0.289, 0.054 and 0.255 for slope, AUC at 1 minute and 4 minutes, and Ktrans, respectively). Slope and 4 minutes AUC significantly associated with growth rate after controlling for Dmax. Conclusion: Contrast uptake may be increased in lateral aspects of the AAA. Contrast enhancement 1‐minute slope and 4‐minutes AUC may be associated with a period of recent AAA growth that is independent of Dmax. Evidence Level: 3. Technical Efficacy: Stage 2. [ABSTRACT FROM AUTHOR]

Introduction: Magnetic resonance elastography (MRE)‐derived aortic stiffness is a potential biomarker for multiple cardiovascular diseases. Currently, gradient‐recalled echo (GRE) MRE is a widely accepted technique to estimate aortic stiffness. However, multi‐slice GRE MRE requires multiple breath‐holds (BHs), which can be challenging for patients who cannot consistently hold their breath. The aim of this study was to investigate the feasibility of a multi‐slice spin‐echo echo‐planar imaging (SE‐EPI) MRE sequence for quantifying in vivo aortic stiffness using a free‐breathing (FB) protocol and a single‐BH protocol. Method: On Scanner 1, 25 healthy subjects participated in the validation of FB SE‐EPI against FB GRE. On Scanner 2, another 15 healthy subjects were recruited to compare FB SE‐EPI with single‐BH SE‐EPI. Among all volunteers, five participants were studied on both scanners to investigate the inter‐scanner reproducibility of FB SE‐EPI aortic MRE. Bland‐Altman analysis, Lin's concordance correlation coefficient (LCCC) and coefficient of variation (COV) were evaluated. The phase‐difference signal‐to‐noise ratios (PD SNR) were compared. Results: Aortic MRE using FB SE‐EPI and FB GRE yielded similar stiffnesses (paired t‐test, P = 0.19), with LCCC = 0.97. The FB SE‐EPI measurements were reproducible (intra‐scanner LCCC = 0.96) and highly repeatable (LCCC = 0.99). The FB SE‐EPI MRE was also reproducible across different scanners (inter‐scanner LCCC = 0.96). Single‐BH SE‐EPI scans yielded similar stiffness to FB SE‐EPI scans (LCCC = 0.99) and demonstrated a low COV of 2.67% across five repeated measurements. Conclusion: Multi‐slice SE‐EPI aortic MRE using an FB protocol or a single‐BH protocol is reproducible and repeatable with advantage over multi‐slice FB GRE in reducing acquisition time. Additionally, FB SE‐EPI MRE provides a potential alternative to BH scans for patients who have challenges in holding their breath. [ABSTRACT FROM AUTHOR]

Stiffness plays an important role in diagnosing renal fibrosis. However, kidney stiffness is altered by perfusion changes in many kidney diseases. Therefore, the aim of the current study is to determine the correlation of kidney stiffness with water intake. We hypothesize that kidney stiffness will increase with 1 L of water intake due to increased water perfusion to the kidneys. Additionally, stiffness of the kidneys will correlate with apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values before and after water intake. A 3 T MRI scanner was used to perform magnetic resonance elastography and diffusion tensor imaging of the kidneys on 24 healthy subjects (age range: 22‐66 years) before and after water intake of 1 L. A 3D T1‐weighted bladder scan was also performed to measure bladder volume before and after water intake. A paired t‐test was performed to evaluate the effect of water intake on the stiffness of kidneys, in addition to bladder volume. A Spearman correlation test was performed to determine the association between stiffness, bladder volume, ADC and FA values of both kidneys before and after water intake. The results show a significant increase in stiffness in different regions of the kidney (ie, percentage increase ranged from 3.6% to 7.5%) and bladder volume after water intake (all P < 0.05). A moderate significant negative correlation was observed between change in kidney stiffness and bladder volume (concordance correlation coefficient = ‐0.468, P < 0.05). No significant correlation was observed between stiffness and ADC or FA values before and after water intake in both kidneys (P > 0.05). Water intake caused a significant increase in the stiffness of the kidneys. The negative correlation between the change in kidney stiffness and bladder volume, before and after water intake, indicates higher perfusion pressure in the kidneys, leading to increased stiffness. [ABSTRACT FROM AUTHOR]

Ascending thoracic aortic aneurysms (aTAAs) can lead to life-threatening dissection and rupture. Recent studies have highlighted aTAA mechanical properties as relevant factors associated with progression. The aim of this study was to quantify in vivo aortic wall stretch in healthy participants and aTAA patients using displacement encoding with stimulated echoes (DENSE) magnetic resonance imaging. Moreover, aTAA wall stretch between surgical and nonsurgical patients was investigated. Finally, DENSE measurements were compared to reference-standard mechanical testing on aTAA specimens from surgical repairs. In total, 18 subjects were recruited, six healthy participants and 12 aTAA patients, for this prospective study. Electrocardiogram-gated DENSE imaging was performed to measure systole-diastole wall stretch, as well as the ratio of aTAA stretch to unaffected descending thoracic aorta stretch. Free-breathing and breath-hold DENSE protocols were used. Uniaxial tensile testing-measured indices were correlated to DENSE measurements in five harvested specimens. in vivo aortic wall stretch was significantly lower in aTAA compared to healthy subjects (1.75±1.44% versus 5.28±1.92%, respectively, P = 0.0004). There was no correlation between stretch and maximum aTAA diameter (P = 0.56). The ratio of aTAA to unaffected thoracic aorta wall stretch was significantly lower in surgical candidates compared to nonsurgical candidates (0.993±0.011 versus 1.017±0.016, respectively, P = 0.0442). Finally, in vivo aTAA wall stretch correlated to wall failure stress and peak modulus of the intima (P = 0.017 and P = 0.034, respectively), while the stretch ratio correlated to whole-wall thickness failure stretch and stress (P = 0.013 and P = 0.040, respectively). Aortic DENSE has the potential to assess differences in aTAA mechanical properties and progressions., (Copyright © 2024 by ASME.)