Compressive Sensing Could Accelerate¹H MR Metabolic Imaging in the Clinic

Abstract

Purpose:To retrospectively evaluate the fidelity of magnetic resonance (MR) spectroscopic imaging data preservation at a range of accelerations by using compressed sensing. Materials and Methods:The protocols were approved by the institutional review board of the university, and written informed consent to acquire and analyze MR spectroscopic imaging data was obtained from the subjects prior to the acquisitions. This study was HIPAA compliant. Retrospective application of compressed sensing was performed on 10 clinical MR spectroscopic imaging data sets, yielding 600 voxels from six normal brain data sets, 163 voxels from two brain tumor data sets, and 36 voxels from two prostate cancer data sets for analysis. The reconstructions were performed at acceleration factors of two, three, four, five, and 10 and were evaluated by using the root mean square error (RMSE) metric, metabolite maps (choline, creatine, N-acetylaspartate [NAA], and/or citrate), and statistical analysis involving a voxelwise paired t test and one-way analysis of variance for metabolite maps and ratios for comparison of the accelerated reconstruction with the original case. Results:The reconstructions showed high fidelity for accelerations up to 10 as determined by the low RMSE (, 0.05). Similar means of the metabolite intensities and hot-spot localization on metabolite maps were observed up to a factor of five, with lack of statistically significant differences compared with the original data. The metabolite ratios of choline to NAA and choline plus creatine to citrate did not show significant differences from the original data for up to an acceleration factor of five in all cases and up to that of 10 for some cases. Conclusion:A reduction of acquisition time by up to 80%, with negligible loss of information as evaluated with clinically relevant metrics, has been successfully demonstrated for hydrogen 1 MR spectroscopic imaging.q RSNA, 20121 From the Joint Graduate Program in Biomedical Engineering at UT Arlington and

Compressed sensing MRI: a review of the clinical literature

“…Many researchers refer to this "simulation" of CS as retrospective CS or retrospective CS reconstruction. [15][16][17]20,23,26,27 Standard undersampling of k-space at acquisition is often referred to as prospective CS or prospective undersampling to distinguish the two methods. Both prospective and retrospective study designs for CS image acquisition were observed among the 18 articles reviewed ( Figure 4).…”

“…15 studies used only one of the 2 designs: 9 studies performed only prospective CS 1,2,18,21,22,24,25,28,29 and 6 studies performed only retrospective CS. [14][15][16][17]19,23 Three studies used both prospective and retrospective CS. 20,26,27 In all three of these cases, CS was retrospectively simulated prior to the performance of prospective CS acquisitions.…”

“…32 A total of 275 subjects were imaged across the 18 studies (range, 3-34; mean 5 15.28; median 5 11.5; standard deviation 5 10.23). 7 studies imaged healthy subjects, 15,[19][20][21]23,24,27 and 11 imaged patients referred for the type of imaging under consideration 1,2,14,[16][17][18]22,25,26,28,29 ( Figure 5). …”

“…contrast uptake or metabolite concentration) was assessed. 2,14,16,17,19,20,24,25 The breakdown of the number of image evaluators included across studies and the degree to which they were blinded to patient or image information is presented in Figures 6 and 7, respectively. Imaging acceleration A wide range of acceleration factors was tested across the 18 studies.…”

“…27 All eight studies that tested acceleration factors up to 23 reported diagnostically acceptable images or images not significantly different from gold standard images at a given degree of undersampling. [15][16][17]19,20,23,26,28 In only two of these studies was acceleration also successfully pushed beyond 23. 15,17 Of the 27 tests of acceleration factors .2, 18 tests were successful while 9 failed to produce acceptable images.…”