Improved carotid intraplaque hemorrhage imaging using a slab-selective phase-sensitive inversion-recovery (SPI) sequence.

Intraplaque hemorrhage in atherosclerotic plaques has been associated with accelerated plaque growth as well as exacerbation of clinical symptoms. The identification of intraplaque hemorrhage using magnetic resonance imaging primarily relies on the detection of methemoglobin on T(1) weighted images. Current techniques are limited by insufficient intraplaque hemorrhage-wall contrast and poor blood suppression. In this study, a slab-selective phase-sensitive inversion-recovery (SPI) technique is proposed by combining a phase-sensitive reconstruction with a T(1) weighted sequence specifically designed to achieve improved intraplaque hemorrhage imaging. The SPI sequence was optimized and then used on ex vivo plaque specimens for histology based validation and intraplaque hemorrhage-wall contrast-to-noise ratio comparison with magnetization-prepared 3D rapid acquisition gradient echo MP-RAGE. SPI and MP-RAGE were also tested on a group of atherosclerosis patients to compare in vivo intraplaque hemorrhage-wall contrast-to-noise ratio and blood suppression effectiveness. On ex vivo specimens SPI had better intraplaque hemorrhage identification accuracy and a significantly higher intraplaque hemorrhage-wall contrast-to-noise ratio (P = 0.01) than MP-RAGE. Similar results were found in the in vivo test: Slab-selective phase-sensitive inversion-recovery provided a significantly improved intraplaque hemorrhage-wall contrast-to-noise ratio (P < 0.01) and blood suppression efficiency (P < 0.01). In conclusion, SPI is a novel technique optimized for intraplaque hemorrhage detection and validated against histology. It has demonstrated its capability for improved in vivo intraplaque hemorrhage identification and blood suppression in atherosclerosis patients.