In vivo spectral editing of phosphorylethanolamine

Purpose: To demonstrate J-difference editing of phosphorylethanolamine (PE) with chemical shifts at 3.22 (PE_3.22) and 3.98 (PE_3.98) ppm, and compare the merits of two editing strategies. Methods: Density-matrix simulations of MEGA-PRESS (Mescher-Garwood PRESS) for PE were performed at TEs ranging from 80 to 200 ms in steps of 2 ms, applying 20-ms editing pulses (ON/OFF) at (1) 3.98/7.5 ppm to detect PE_3.22 and (2) 3.22/7.5 ppm to detect PE_3.98. Phantom experiments were performed using a PE phantom to validate simulation results. Ten subjects were scanned using a Philips 3T MRI scanner at TEs of 90 ms and 110 ms to edit PE_3.22 and PE_3.98. Osprey was used for data processing, modeling, and quantification. Results: Simulations show substantial TE modulation of the intensity and shape of the edited signals due to coupling evolution. Simulated and phantom integrals suggest that TEs of 110 ms and 90 ms were optimal for the edited detection of PE_3.22 and PE_3.98, respectively. Phantom results indicated strong agreement with the simulated spectra and integrals. In vivo quantification of the PE_3.22/total creatine and PE_3.98/total creatine concentration ratio yielded values of 0.26 ± 0.04 (between-subject coefficient of variation [CV]: 15.4%) and 0.18 ± 0.04 (CV: 22.8%), respectively, at TE = 90 ms, and 0.24 ± 0.02 (CV: 8.2%) and 0.23 ± 0.04 (CV: 18.0%), respectively, at TE = 110 ms. Conclusion: Simulations and in vivo MEGA-PRESS of PE demonstrate that both PE_3.22 and PE_3.98 are potential candidates for editing, but PE_3.22 at TE = 110 ms yields lower variation across TEs. Keywords: Magnetic resonance spectroscopy, MEGA-PRESS, spectral editing, phosphorylethanolamine.