7T TOF-MRA in Adolescents

Abstract

Background and purpose: The increased SNR at 7T enables higher spatial resolution for neurovascular imaging, yet its application in pediatric MRA remains underexplored. This study systematically evaluates the advantages of 7T TOF-MRA compared with 3T in pediatric patients, hypothesizing that 7T would provide superior vessel contrast and increased vascular volume, given the use of smaller voxels, as well as higher SNR, despite these smaller voxels.

Materials and methods: This Health Insurance Portability and Accountability Act (HIPAA)-compliant, institutional review board-approved retrospective study included pediatric patients (younger than 19 years of age) who underwent 7T TOF-MRA. Controls consisted of either same-subject 3T MRAs within 6 months (when available) or age- and sex-matched 3T MRA subjects. Imaging parameters were optimized for spatial resolution at 7T to achieve 0.3- to 0.4-mm isotropic voxels. Quantitative analysis included contrast ratio and SNR measurements for the ICA, M1 to M4 arterial segments, and the lenticulostriate perforating arteries. Vascular volume was assessed using 3D segmentation. Semiquantitative vessel conspicuity ratings and motion artifact scoring were performed by blinded neuroradiologists.

Results: Fifteen patients (10 with 7T MRA, 5 with matched 3T controls) and 20 MRAs were analyzed. Contrast ratio was significantly higher at 7T for perforators, M3, and M4 branches (P < .05), with the greatest improvement in the M4 branches. Vascular volume was 147% greater at 7T (P = .018), reflecting improved small-vessel depiction and segmentation. Semiquantitative analysis showed significantly better vessel conspicuity at 7T for the M4 branches and lenticulostriate perforators (P < .01). Motion artifact scores were similar between field strengths (P = .118).

Conclusions: 7T TOF-MRA significantly enhances vascular contrast and improves visualization of small arteries compared with 3T, making it a valuable tool for pediatric cerebrovascular imaging.