Highly accelerated whole-brain T₂ mapping using non-cartesian acquisition and model-based implicit neural...

To propose a technique for highly accelerated T₂ mapping of the whole brain.

A pulse sequence with T₂ preparation and a highly undersampled golden-angle stack-of-stars trajectory is used for data acquisition. A multiresolution hash encoding implicit neural representation, embedded with a physical model of signal evolution, is employed for unsupervised reconstruction. By rotating the trajectory at different kz encodings and effective echo times (TE_eff) during acquisition, undersampling is applied to three dimensions, i.e., (kx, ky, TE_eff) domain. In the phantom experiment, T₂ quantification using this T₂-prepared stack-of-stars acquisition was compared with that using a Cartesian multi-echo spin-echo acquisition. In the human experiments, T₂ quantification using the undersampled acquisition was validated in comparison with those using the fully sampled acquisition and multi-echo spin-echo.

In phantom test, T₂ quantification using the proposed reconstruction agreed well (slope = 0.999, R² > 0.99) with that obtained by fitting the NUFFT-reconstructed results for the fully sampled T₂-prepared stack-of-stars acquisition. In human experiments, T₂ quantification using a 20-fold acceleration agreed well with that using fully sampled data (NRMSE = 0.0066) in retrospectively undersampled reconstruction. No significant difference in T₂ values was found between our technique and the reference method in prospective experiments, and our technique showed good inter-scan reproducibility and intra-scan repeatability.

Using the proposed technique, whole-brain T₂ mapping can be acquired in 70 s with a 20-fold acceleration.