Accelerated Echo Planar J-Resolved Spectroscopic Imaging in Prostate Cancer: A Pilot Validation of Non-linear Reconstruction Using Total Variation And Maximum Entropy

摘要

Overlap of metabolites is a major limitation in one-dimensional (1D) spectral-based single voxel MR Spectroscopy (MRS) and multivoxel-based MR spectroscopic imaging (MRSI). By combining echo-planar spectroscopic imaging (EPSI) with two-dimensional (2D) J resolved spectroscopic sequence (JPRESS), 2D spectra can be recorded in multiple locations in a single slice of prostate using four dimensional (4D) Echo-Planar J-Resolved Spectroscopic Imaging (EP-JRESI). The goal of the present work was to validate two different non-linear reconstruction methods independently using compressed sensing based 4D EP-JRESI in Prostate Cancer (PCa): Maximum Entropy (MaxEnt) and Total Variation (TV). Twenty two prostate cancer patients with a mean age of 63.8 years (range: 46–79 years) were investigated in this study. A 4D non-uniformly under-sampled (NUS) EP-JRESI sequence was implemented on the Siemens 3T MRI scanner. The NUS data was reconstructed using two non-linear reconstruction methods, namely MaxEnt and TV. Using both TV and MaxEnt reconstruction methods, following observations were made in cancer compared to non-cancerous locations: 1) higher mean (Ch+Cr)/Cit metabolite ratios. 2) Increased levels of (Ch+Cr)/Spm, (Ch+Cr)/mI and decreased levels of (Ch+Cr)/Glx. We have shown that it is possible to accelerate the 4D EP-JRESI sequence by 4X and that the data can be reliably reconstructed using the TV and MaxEnt methods. The total acquisition duration was less than 13 minutes and we were able to detect and quantify several metabolites.