Compressed‐Sensing MP2RAGE sequence: Application to the detection of brain metastases in mice at 7T

Purpose To develop a Compressed Sensing (CS)‐MP2RAGE sequence to drastically shorten acquisition duration and then detect and measure the T 1 of brain metastases in mice at 7 T. Methods The encoding trajectory of the standard Cartesian MP2RAGE sequence has been modified (1) to obtain a variable density Poisson disk under‐sampling distribution along the k y ‐k z plane, and (2) to sample the central part of the k‐space exactly at TI 1 and TI 2 inversion times. In a prospective study, the accuracy of the T 1 measurements was evaluated on phantoms containing increasing concentrations of gadolinium. The CS acceleration factors were increased to evaluate their influence on the contrast and T 1 measurements of brain metastases in vivo. Finally, the 3D T 1 maps were acquired with at 4‐fold increased spatial resolution. The volumes and T 1 values of the metastases were measured while using CS to reduce scan time. Results The implementation of the CS‐encoding trajectory did not affect the T 1 measurements in vitro. Accelerating the acquisition by a factor of 2 did not alter the contrast or the T 1 values of the brain metastases. 3D T 1 maps could be obtained in < 1 min using a CS factor of 6. Increasing the spatial resolution enabled more accurately measurement of the metastasis volumes while maintaining an acquisition duration below 5 min. Conclusion The CS‐MP2RAGE sequence could be of great interest in oncology to either rapidly obtain mouse brain 3D T 1 maps or to increase the spatial resolution with no penalty on the scan duration.