Nonuniform sliding-window reconstruction for accelerated dual contrast agent quantification with MR fingerprinting

Abstract

Objective

MR fingerprinting (MRF) can enable preclinical studies of cell tracking by quantifying multiple contrast agents simultaneously, but faster scan times are required for in vivo applications. Sliding window (SW)-MRF is one option for accelerating MRF, but standard implementations are not sufficient to preserve the accuracy of T₂*, which is critical for tracking iron-labelled cells in vivo.

Purpose

To develop a SW approach to MRF which preserves the T₂* accuracy required for accelerated concentration mapping of iron-labelled cells on single-channel preclinical systems.

Methods

A nonuniform SW was applied to the MRF sequence and dictionary. Segments of the sequence most sensitive to T₂* were subject to a shorter window length, preserving the T₂* sensitivity. Phantoms containing iron-labelled CD8+ T cells and gadolinium were used to compare 24× undersampled uniform and nonuniform SW-MRF parameter maps. Dual concentration maps were generated for both uniform and nonuniform MRF and compared.

Results

Lin’s concordance correlation coefficient, compared to gold standard parameter values, was much greater for nonuniform SW-MRF than for uniform SW-MRF. A Wilcoxon signed-rank test showed no significant difference between nonuniform SW-MRF and gold standards. Nonuniform SW-MRF outperformed the uniform SW-MRF concentration maps for all parameters, providing a balance between T₂* sensitivity of short window lengths, and SNR of longer window lengths.

Conclusions

Nonuniform SW-MRF improves the accuracy of matching compared to uniform SW-MRF, allowing higher accelerated concentration mapping for preclinical systems.