Investigative Radiology

Ultrasound Time-Harmonic Elastography of the Aorta: Effect of Age and Hypertension on Aortic Stiffness Objectives The aim of this study was to investigate ultrasound time-harmonic elastography for quantifying aortic stiffness in vivo in the context of aging and arterial hypertension. Materials and Methods Seventy-four participants (50 healthy participants and 24 participants with long-standing hypertension) were prospectively included between January 2018 and October 2018, and underwent ultrasound time-harmonic elastography of the upper abdominal aorta. Compound maps of shear-wave speed (SWS) as a surrogate of tissue stiffness were generated from multifrequency wave fields covering the full field-of-view of B-mode ultrasound. Blood pressure and pulse wave velocity were measured beforehand. Interobserver and intraobserver agreement was determined in 30 subjects. Reproducibility of time-harmonic elastography was assessed in subgroups with repeated measurements after 20 minutes and after 6 months. Linear regression analysis, with subsequent age adjustment of SWS obtained, receiver operating characteristic analysis, and intraclass correlation coefficients (ICCs) were used for statistical evaluation. Results Linear regression analysis revealed a significant effect of age on SWS with an increase by 0.024 m/s per year (P < 0.001). Age-adjusted SWS was significantly greater in hypertensives (0.24 m/s; interquartile range [IQR], 0.17–0.40 m/s) than in healthy participants (0.07 m/s; IQR, −0.01 to 0.06 m/s; P < 0.001). A cutoff value of 0.15 m/s was found to differentiate best between groups (area under the receiver operating characteristic curve, 0.966; 95% confidence interval, 0.93–1.0; P < 0.001; 83% sensitivity and 98% specificity). Interobserver and intraobserver variability was excellent (ICC, 0.987 and 0.937, respectively). Reproducibility was excellent in the short term (ICC, 0.968; confidence interval, 0.878–0.992) and good in the long term (ICC, 0.844; confidence interval, 0.491–0.959). Conclusions Ultrasound time-harmonic elastography of the upper abdominal aorta allows quantification of aortic wall stiffness in vivo and shows significantly higher values in patients with arterial hypertension. Received for publication February 6, 2019; and accepted for publication, after revision, May 10, 2019. Conflicts of interest and sources of funding: This study was in part funded by a research grant from the German Research Foundation (Bonn, Germany) to Thomas Elgeti (grant number: EL606/2-1). The authors gratefully acknowledge support from the German Research Foundation (GRK2260 BIOQIC, SFB1340 Matrix-in-Vision). Supplemental digital contents are available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.investigativeradiology.com). Correspondence to: Thomas Elgeti, MD, Department of Radiology, Charité–Universitätsmedizin Berlin, Hindenburgdamm 30, 12203 Berlin, Germany. E-mail: thomas.elgeti@charite.de. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Free-Breathing Fast Low-Angle Shot Quiescent-Interval Slice-Selective Magnetic Resonance Angiography for Improved Detection of Vascular Stenoses in the Pelvis and Abdomen: Technical Development Objectives Balanced steady-state free precession-based quiescent-interval slice-selective (bSSFP QISS) magnetic resonance angiography (MRA) is accurate for the noncontrast evaluation of peripheral arterial disease (PAD); however, drawbacks include the need for breath-holding when imaging the abdomen and pelvis, and sensitivity to off-resonance artifacts. The purpose of this study was to evaluate the image quality and diagnostic accuracy in the pelvis and abdomen of free-breathing fast low-angle shot-based QISS (FLASH QISS) techniques in comparison to bSSFP QISS in patients with PAD, using computed tomographic angiography as the reference. Materials and Methods Twenty-seven patients (69 ± 10 years, 17 men) with PAD were enrolled in this institutional review board–approved, Health Insurance Portability and Accountability Act–compliant prospective study between April and December 2018. Patients underwent noncontrast MRA using standard bSSFP QISS and prototype free-breathing radial-FLASH and Cartesian-FLASH QISS at 3 T. A subset of patients (n = 22) also underwent computed tomographic angiography as the reference standard. Nine arterial segments per patient were evaluated spanning the abdomen, pelvis, and upper thigh regions. Objective (signal intensity ratio and relative standard deviation) and subjective image quality (4-point scale) and stenosis (>50%) were evaluated by 2 readers and compared using one-way analysis of variance, Wilcoxon, and McNemar tests, respectively. Results A total of 179 vascular segments were available for analysis by all QISS techniques. No significant difference was observed among bSSFP, radial-FLASH, and Cartesian-FLASH QISS techniques in signal intensity ratio (P = 0.428) and relative standard deviation (P = 0.220). Radial-FLASH QISS demonstrated the best image quality (P < 0.0001) and the highest interreader agreement (κ = 0.721). The sensitivity values of bSSFP, radial-FLASH, and Cartesian-FLASH QISS for the detection of greater than 50% stenosis were 76.0%, 84.0%, and 80.0%, respectively, whereas specificity values were 97.6%, 94.0%, and 92.8%, respectively. Moreover, FLASH QISS consistently reduced off-resonance artifacts compared with bSSFP QISS. Conclusions Free-breathing FLASH QISS MRA techniques provide improved image quality and sensitivity, high specificity, and reduced off-resonance artifacts for vascular stenosis detection in the abdomen and pelvis. Received for publication April 19, 2019; and accepted for publication, after revision, May 19, 2019. Conflicts of interest and sources of funding: U. Joseph Schoepf is a consultant for and/or receives research support from Astellas, Bayer, Elucid Bioimaging, Guerbet, HeartFlow Inc, and Siemens Healthcare. Akos Varga-Szemes receives institutional research and travel support from Siemens Healthcare and is a consultant for Elucid Bioimaging. Robert R. Edelman receives grant support and royalties from Siemens Healthcare. Ioannis Koktzoglou receives research support from Siemens Healthcare. This study was supported by NIH NHLBI R01 HL130093 (R.R.E.). Correspondence to: Robert R. Edelman, MD, Department of Radiology, NorthShore University HealthSystem, Walgreen Bldg, G534, 2650 Ridge Ave, Evanston, IL 60201. E-mail: redelman999@gmail.com. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.