In vivo lactate editing in single voxel proton spectroscopy and proton spectroscopic imaging by homonuclear polarisation transfer.

Volume-selective lactate editing has been performed successfully in vitro and in vivo in the brain on a clinical scanner using a PRESS-based single voxel 1H spectroscopy and a 1H spectroscopic imaging sequence. The PRESS sequence was made sensitive to homonuclear polarisation by replacing the standard 180 degree refocusing pulses with 90 degree pulses. Two acquisitions were made at a total echo time around 2/J (J is the coupling constant for CH and CH3 spins in lactate approximately 7 Hz) whose individual echo times differed by 5.5 ms. Subtraction of one signal from the other yielded the lactate resonance alone. The technique is an effective method of separating the overlapping signals of lactate and lipids. Furthermore this editing method can be performed without state of the art MRI scanner hardware.