Lactate quantitation in a gerbil brain stroke model by GSLIM of multiple-quantum-filtered signals. Generalized spectral localization by imaging.

Quantitative magnetic resonance imaging of lactate using a zero-quantum/double-quantum filter and generalized spectral localization by imaging (GSLIM) was applied to a model of unilateral stroke in gerbil brain. GSLIM lactate images at 4T clearly reveal elevated concentrations of lactate in the ischemic compared with the normal hemisphere 100-175 minutes after unilateral carotid ligation. These results indicate that the technique is capable of studies of brain infarcts, and that application to human ischemic pathology in brain and other tissues may be possible.

Quantitative lactate-specific MR imaging and 1H spectroscopy of skeletal muscle at macroscopic and microscopic resolutions using a zero-quantum/double-quantum coherence filter and SLIM/GSLIM localization.

Quantitative lactate imaging and spectroscopy were performed on phantoms and on electrically stimulated, excised frog skeletal muscle at macroscopic and microscopic resolutions. Lactate selectivity was achieved by use of a zero-quantum/double-quantum coherence (ZQC/DQC) lactate filter, which suppressed all signals besides lactate, including water and lipid, to below noise level. Three-dimensional lactate data sets were acquired in 1-3 h; one of these spatial dimensions was frequency-encoded and the other two were phase-encoded. High-resolution images were reconstructed using the spectral localization by imaging (SLIM) and generalized SLIM (GSLIM) techniques. Lactate quantitation was achieved by employing an external lactate concentration standard and was verified by comparison to quantitative STEAM-localized and nonlocalized spectra that used total creatine as an internal concentration reference. Additionally, quantitatively accurate behavior of the SLIM and GSLIM techniques as applied to data sets of low signal-to-noise ratio and to macroscopically heterogeneous objects was verified using simulations and real muscle lactate data sets with known heterogeneity.