Free‐breathing 3D cardiac T₁mapping with transmit B₁correction at 3T

Abstract

Purpose To develop a cardiac T 1 mapping method for free‐breathing 3D T 1 mapping of the whole heart at 3 T with transmit B 1 ( ) correction. Methods A free‐breathing, electrocardiogram‐gated inversion‐recovery sequence with spoiled gradient‐echo readout was developed and optimized for cardiac T 1 mapping at 3 T. High‐frame‐rate dynamic images were reconstructed from sparse (k,t)‐space data acquired along a stack‐of‐stars trajectory using a subspace‐based method for accelerated imaging. Joint T 1 and flip‐angle estimation was performed in T 1 mapping to improve its robustness to inhomogeneity. Subject‐specific timing of data acquisition was used in the estimation to account for natural heart‐rate variations during the imaging experiment. Results Simulations showed that accuracy and precision of T 1 mapping can be improved with joint T 1 and flip‐angle estimation and optimized electrocardiogram‐gated spoiled gradient echo–based inversion‐recovery acquisition scheme. The phantom study showed good agreement between the T 1 maps from the proposed method and the reference method. Three‐dimensional cardiac T 1 maps (40 slices) were obtained at a 1.9‐mm in‐plane and 4.5‐mm through‐plane spatial resolution from healthy subjects (n = 6) with an average imaging time of 14.2 ± 1.6 minutes (heartbeat rate: 64.2 ± 7.1 bpm), showing myocardial T 1 values comparable to those obtained from modified Look‐Locker inversion recovery. The proposed method generated maps with spatially smooth variation showing 21%–32% and 11%–15% variations across the septal–lateral and inferior–anterior regions of the myocardium in the left ventricle. Conclusion The proposed method allows free‐breathing 3D T 1 mapping of the whole heart with transmit B 1 correction in a practical imaging time.