Rapid, High-resolution and Distortion-free R2* Mapping of Fetal Brain using Multi-echo Radial FLASH and Model-based Reconstruction

Motivation: Quantitative R2*mapping of fetal brain is of great interest. While existing EPI-based approaches are efficient, they may suffer from low spatial resolution and field distortion artifacts. Goal(s): To develop a rapid, high-resolution and distortion-free quantitative R2* mapping approach for fetal brain. Approach: A 2D radial multi-echo FLASH sequence with blip gradients is adapted for data acquisition. A nonlinear model-based reconstruction is developed to estimate motion-robust quantitative fetal brain maps directly from k-space. Results: Validated on simulations, NIST phantoms, and fetuses, the proposed technique achieves distortion-free quantitative R2* maps at a nominal spatial resolution of 1.1 x 1.1 x 3 mm³ within 2 seconds. Impact: Our technique enables high-resolution, distortion-free R2* mapping of the fetal brain using radial multi-echo acquisition and model-based reconstruction. This approach overcomes the low resolution and field distortion artifacts common in EPI-based methods.