Three-dimensional black-blood T₂ mapping with compressed sensing and data-driven parallel imaging in the carotid...

To develop a 3D black-blood T₂ mapping sequence with a combination of compressed sensing (CS) and parallel imaging (PI) for carotid wall imaging.

A 3D black-blood fast-spin-echo (FSE) sequence for T₂ mapping with CS and PI was developed and validated. Phantom experiments were performed to assess T₂ accuracy using a Eurospin Test Object, with different combination of CS and PI acceleration factors. A 2D multi-echo FSE sequence was used as a reference to evaluate the accuracy. The concordance correlation coefficient and Bland-Altman statistics were calculated. Twelve volunteers were scanned twice to determine the repeatability of the sequence and the intraclass correlation coefficient (ICC) was reported. Wall-lumen sharpness was calculated for different CS and PI combinations. Six patients with carotid stenosis >50% were scanned with optimised sequence. The T₂ maps were compared with multi-contrast images.

Phantom scans showed good correlation in T₂ measurement between current and reference sequence (r=0.991). No significant difference was found between different combination of CS and PI accelerations (p=0.999). Volunteer scans showed good repeatability of T₂ measurement (ICC: 0.93, 95% CI 0.84-0.97). The mean T₂ of the healthy wall was 48.0±9.5ms. Overall plaque T₂ values from patients were 54.9±12.2ms. Recent intraplaque haemorrhage and fibrous tissue have higher T₂ values than the mean plaque T₂ values (88.1±6.8ms and 62.7±9.3ms, respectively).

This study demonstrates the feasibility of combining CS and PI for accelerating 3D T₂ mapping in the carotid artery, with accurate T₂ measurements and good repeatability.