Shortening 7T MP2RAGE acquisition with compressed sensing: Evaluating quantitative accuracy and structural consistency

TL;DR

This study shows that compressed sensing can significantly shorten MRI scan times while maintaining image quality and accuracy in T1 mapping.

Contribution

The study introduces a method to optimize compressed sensing in MP2RAGE for ultra-high field MRI, balancing speed and accuracy.

Findings

CS-MP2RAGE reduced acquisition time by 61% while maintaining image quality and T1 mapping accuracy.

Higher undersampling factors introduced segmentation mismatches and increased T1 values.

Reducing samples per TR improved image quality but excessive reduction caused reconstruction instability.

Abstract

The aim of this study was to systematically evaluate the impact of compressed sensing (CS) on acquisition time, image quality, T1 mapping accuracy, and segmentation consistency in magnetization-prepared 2 rapid acquisition gradient echo (MP2RAGE) at ultra-high fields (UHF). MP2RAGE sequences were acquired using the CS and parallel imaging (PI) technique, i.e., generalized autocalibrating partially parallel acquisitions (GRAPPA), with varying undersampling factors and samples per repetition time (TR). The acquisition time, quantitative accuracy of T1 mapping, and segmentation consistency across regions of interest (ROIs) were assessed. CS-MP2RAGE achieved a 61% reduction in acquisition time (< 3 min) compared with PI-MP2RAGE and maintained comparable image quality, segmentation accuracy, and T1-mapping fidelity. Higher undersampling factors effectively reduced scan duration but introduced segmentation volume mismatches of up to 20% and increased T1 values, despite the images appearing similar to PI-MP2RAGE. Reducing the number of samples per TR enhanced image quality, allowing for higher undersampling factors without a significant loss of fidelity, a finding consistent with previous studies. However, excessively low sampling densities destabilized reconstruction in complex ROIs. Our findings demonstrate that CS-MP2RAGE significantly reduces scan time while maintaining high image quality and quantitative accuracy, making it a viable alternative to GRAPPA in UHF applications. The interplay between undersampling factors and samples per TR is crucial for optimizing scan efficiency. Future studies should explore its application in clinical and research settings.

Figures