Room: Room 205
Purpose: To evaluate the impact of the 5.2 ppm triglyceride glycerol proton contamination on olefinic proton quantification (a measure of fat unsaturation) using the in-vivo Magnetic Resonance Spectroscopy (MRS) techniques Point RESolved Spectroscopy (PRESS) and Simulated Echo Acquisition Mode (STEAM) at 3 T, a field strength becoming more commonly used in the clinic.
Methods: MRS spectra were acquired from the triglyceride tricaprylin (contains glycerol but no olefinic protons), and from free oleic acid (contains olefinic but no glycerol protons) using PRESS (echo time, TE = 40 to 300 ms, 10 ms intervals) and STEAM (TE = 20 to 300 ms, 10 ms intervals, mixing time = 20 ms) at 3 T. The glycerol resonance peak areas (tricaprylin) and olefinic resonance peak areas (oleic acid) were normalized to signal acquired with short TE, and plotted as a function of TE. Echo times which yielded normalized olefinic signals â‰¥ 25 % and normalized glycerol signals â‰¤ 5 % were investigated further. Of these, the echo times which yielded the largest difference between glycerol and olefinic resonance areas were selected for olefinic resonance quantification.
Results: A TE of 90 ms for STEAM and a TE of 200 ms for PRESS were selected for reducing glycerol contamination on the olefinic resonance. The signal yields relative to the short-TE spectra for the olefinic and glycerol protons are 29 % and 5 %, respectively, for PRESS (TE of 200 ms). For STEAM (TE = 90 ms), the relative signal yields are 30 % and 4 % for the olefinic protons and glycerol protons, respectively.
Conclusion: A STEAM sequence with a TE of 90 ms and a PRESS sequence with a TE of 200 ms are suitable for quantifying fat olefinic signal with minimal contamination from the 5.2 ppm glycerol protons at 3 T.