Distortion-free steady-state diffusion-weighted imaging with magnetic resonance fingerprinting

Background

Magnetic resonance fingerprinting (MRF) could provide joint T1, T2, and proton density mapping. Measuring diffusion encoding using the MRF framework is promising, given its capacity to generate self-aligned quantitative maps and contrast-weighted images from a single scan. It could avoid potential errors that arise from the registration of multiple MRI images and reduce the total scan time. However, the application of a strong diffusion gradient on the MRF sequence results in phase inconsistency between acquisitions, which could corrupt the reconstructed images.

Purpose

To propose a distortion-free diffusion-weighted imaging module for MRF (DWI-MRF) method using a self-navigated subspace reconstruction on k-space data obtained from a dual-density spiral trajectory.

Methods

The proposed sequence consisted of two segments: inversion prepared steady-state free precession MRF for the first 800 time points and diffusion-weighted imaging (DWI) with two nominal b-values of 0 and 800 s/mm² for the following 200 time points. The temporal basis was acquired from the densely sampled central k-space during reconstruction. The subspace reconstruction was applied to generate aliasing-free and high-resolution images at each time point. The cardiac gating was retrospectively performed on the high-resolution and dynamic DWI images. Our T1, T2, and apparent diffusion coefficient (ADC) results were compared to conventional methods on a phantom and two healthy volunteers.

Results

Our method's T1, T2, and ADC values agreed reasonably with the reference values, with a slope of 0.88, 0.94, and 1.04 for T1, T2, and ADC, and an R² value of 0.97, 0.97, and 0.71, respectively. The T1, T2, and ADC maps from DWI-MRF exhibited pixel-by-pixel correspondence on phantom and in vivo (T1 and ADC: R² = 0.75 on phantom and 0.84 in vivo; T2 and ADC: R² = 0.79 and 0.83, respectively). Our method achieved high acquisition efficiency, requiring less than 20 s per slice.

Conclusions

The proposed method was free of artifacts from cardiac pulsation and generated pixel-wise correspondent T1, T2, and ADC maps on both phantom and in vivo images.