An efficient chemical shift imaging scheme for magnetic resonance-guided neurosurgery

An efficient magnetic resonance spectroscopic imaging (MRSI) or chemical sh ift Imaging (CSI) technique based on multiple spin echoes (MSE) has been im plemented, validated, and used In both phantom and In vivo AIR-guided neuro surgical applications. The key concept of the method is to employ MSE to si gnificantly speed up the data collection rate for mapping hydrogen-containi ng metabolites. Using an echo train length (ETL) of three per excitation to simultaneously fill three consecutive k-space areas, the total scan time f or a spectroscopic image matrix size of 32 X 32 has been shortened to appro ximately I I minutes. An interecho spacing time of 273 msec was used to nul l the phase anomalies of lactate double peaks due to the J-coupling. This a llowed a sufficient long data sampling time to achieve 4 Hz spectral resolu tion. Performing CSI intraopertively during an MR-guided neurosurgical proc edure was shown to be feasible at 1.5 T. More Importantly, it was shown tha t more relevant Information can be obtained regarding neurochemistry about a targeted lesion, in addition to conventional MR morphological imaging non invasively. In 25 MR-guided neurosurgical cases, the alleviated choline sig nal has been found to be consistent with the existence of rapid tumor cell proliferation in the corresponding area. The actual neurobiopsy guided by t he spectroscopic imaging method demonstrate that it could provide valuable information in specifying the optimal site in a biopsy procedure, especiall y in the case Involving a nonenhancing tumor. The multiecho scheme has made the CSI technique efficient enough to be routinely used In MR-guided surgi cal procedures at 1.5 T and also allows the possibility of taking full adva ntage of MRI capability. (C) 2001 Wiley-Liss, Inc.