Extracting more for less: multi‐echo MP2RAGE for simultaneous T₁‐weighted imaging, T₁ mapping, mapping, SWI, and QSM from a single acquisition

Abstract

* 2 mapping, SWI, and QSM from a single multi-echo (ME) MP2RAGE acquisition. Methods: A single-echo (SE) MP2RAGE sequence at 7 tesla was extended to ME with 4 bipolar gradient echo readouts. T 1-weighted images and T 1 maps calculated from individual echoes were combined using sum of squares and averaged, respectively. ME-combined SWI and associated minimum intensity projection images were generated with TE-adjusted homodyne filters. A QSM reconstruction pipeline was used, including a phase-offsets correction and coil combination method to properly combine the phase images from the 32 receiver channels. Measurements of susceptibility, R * 2 , and T 1 of brain tissue from ME-MP2RAGE were compared with those from standard ME-gradient echo and SE-MP2RAGE. Results: The ME combined T 1-weighted, T 1 map, SWI, and minimum intensity projection images showed increased SNRs compared to the SE results. The proposed coil combination method led to QSM results free of phase-singularity artifacts, which were present in the standard adaptive combination method. T 1-weighted, T 1 , and susceptibility maps from ME-MP2RAGE were comparable to those obtained from SE-MP2RAGE and ME-gradient echo, whereas R * 2 maps showed increased blurring and reduced SNR. T 1 , R * 2 , and susceptibility values of brain tissue from ME-MP2RAGE were consistent with those from SE-MP2RAGE and ME-gradient echo. Conclusion: High-resolution structural T 1 weighted imaging, T 1 mapping, R * 2 mapping, SWI, and QSM can be extracted from a single 8.5-min ME-MP2RAGE acquisition using a customized reconstruction pipeline. This method can be applied to replace separate SE-MP2RAGE and ME-gradient echo acquisitions to significantly shorten total scan time.

Fast automatic segmentation of thalamic nuclei from MP2RAGE acquisition at 7 Tesla

“…A single ME-MP2RAGE sequence can yield multiple quantitative maps of tissue relaxometry such as T1, T * 2 and SWI in a favorable acquisition time over multiple separate sequences for each. 35,39,40 The T1 values obtained with ME-MP2RAGE and the single echo MP2RAGE sequence show excellent agreement across brain regions and the T * 2 and susceptibility weighted imaging (SWI) maps are of comparable quality to those obtained from Fast Low-Angle SHot (FLASH) data. 35,39,40 The 20 priors in the THOMAS multi-atlas 34 included 11 datasets from adult MS patients.…”

On the value of QSM from MPRAGE for segmenting and quantifying iron‐rich deep gray matter

“…New MPRAGE versions have been proposed recently, known as MP2RAGE, MPnRAGE, and ME‐MP2RAGE, which use two or more inversion times and may collect multiple echoes. For versions such as MP2RAGE, that maintain a single short TE for both optimal SNR and T1w contrast, the same methods used here could be applied.…”

“…In this study, we examine the possibility of using MPRAGE phase directly for QSM. Although new multi‐echo versions of MP2RAGE are capable of providing multiple contrasts including both T1 and QSM, to our knowledge standard MPRAGE used in most volumetric studies has not been used for creating QSM. Here, we evaluate the creation of QSM directly from standard volumetric MPRAGE data to achieve improved segmentation over MPRAGE magnitude and susceptibility quantification of highly iron‐rich DGM nuclei.…”

Methodological Considerations for Neuroimaging in Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson’s Disease Patients

“…Multi-contrast sequences may offer a novel alternative for eliminating the requirement of registration and resampling of separate scans while simultaneously reducing scan acquisition time ( Figure 2 ) [ 152 ]. A recently developed multiparametric imaging sequence is the Multi Echo (ME) MP2RAGE, which is largely unaffected by B1 inhomogeneities [ 153 , 154 , 155 , 156 , 157 , 158 , 159 , 160 ]. This allows for the acquisition of T2*-based contrasts from which subsequent SWI and quantitative susceptibility maps (QSM) can be created in the same space as the T1 images [ 158 , 160 ].…”

“…A frequently used method to create T2* maps is done by fitting an exponential decay curve to the signal intensities per pixel from each of the multiple echoes obtained from a GRE sequence [ 212 ]. Moreover, the pixel intensities of reciprocal T2* maps (R2*) are proportional to iron load, with STN R2* values hovering around 67 s −1 (1/15 ms) at 7 T [ 155 , 213 , 214 , 215 , 216 ]. Alternatively, T2* images can be post-processed to create quantitative susceptibility maps (QSM), which quantify a tissue’s magnetic susceptibility distribution on the basis of its perturbation of the magnetic field [ 213 ].…”