Respiratory-Resolved Isotropic 3D T₁ Mapping of the Carotid Vessel Wall With B₁ ⁺ Correction (CARISMAT1C)

To develop, optimize, and characterize a respiratory motion-resolved free-running isotropic 3D carotid vessel wall T₁ mapping technique named CARISMAT1C.

An inversion-recovery gradient-echo free-running pulse sequence with interleaved double flip-angle (2FA) was implemented, and an extended-phase-graph dictionary was used to map the T₁ relaxation time. In a phantom, the T₁ accuracy was compared to that of a single-flip-angle (1FA) variant, the inversion-recovery spin-echo reference, and clinical routine MOLLI, while the T₁ precision of several phyllotaxis-based radial trajectories was compared. The most precise sequence was used in 11 healthy volunteers (25 ± 3Y, 3F). A synthetic 3D gray-blood image was reconstructed from the source images and used to delineate the internal, external, and common carotid arteries. T₁ values across artery sections were compared to those of MOLLI.

In the phantom, the 2FA variant had higher T₁ agreement with the IR-SE reference than 1FA or MOLLI. The top-to-bottom phyllotaxis trajectory with golden-step shuffling was the most precise and was retained for in vivo scans. End-expiratory carotid vessel wall T₁ values (1185 ± 42 ms) were similar to those obtained with MOLLI (1162 ± 84 ms, p = 0.37) and showed less intersubject variability and high interscan repeatability. No significant differences were found across arterial segments in the vessel wall T₁ values.

CARISMAT1C had high T₁ accuracy in phantoms and high T₁ precision in vivo in different sections of the carotid artery tree.