Three-dimensional quantitative T<inf>1</inf> and T<inf>2</inf> mapping of the carotid artery

Purpose: A novel three-dimensional (3D) T1 and T2 mapping protocol for the carotid artery is presented.
Methods: A 3D black-blood imaging sequence was adapted allowing carotid T1 and T2 mapping using multiple flip angles and echo time (TE) preparation times. B1 mapping was performed to correct for spatially varying deviations from the nominal flip angle. The protocol was optimized using simulations and phantom experiments. In vivo scans were performed on six healthy volunteers in two sessions, and in a patient with advanced atherosclerosis. Compensation for patient motion was achieved by 3D registration of the inter/intrasession scans. Subsequently, T1 and T2 maps were obtained by maximum likelihood estimation.
Results: Simulations and phantom experiments showed that the bias in T1 and T2 estimation was<10% within the range of physiological values. In vivo T1 and T2 values for carotid vessel wall were 844696 and 3965 ms, with good repeatability across scans. Patient data revealed altered T1 and T2 values in regions of atherosclerotic plaque.
Conclusion: The 3D T1 and T2 mapping of the carotid artery is feasible using variable flip angle and variable TE preparation acquisitions. We foresee application of this technique for plaque characterization and monitoring plaque progression in atherosclerotic patients.