QUANTITATIVE LACTATE-SPECIFIC MR-IMAGING AND H-1 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 phanto ms and on electrically stimulated, excised frog skeletal muscle at mac roscopic and microscopic resolutions. Lactate selectivity was achieved by use of a zero-quantum/double-quantum coherence (ZQC/DQC) lactate f ilter, which suppressed all signals besides lactate, including water a nd lipid, to below noise level. Three-dimensional lactate data sets we re acquired in 1-3 h; one of these spatial dimensions was frequency-en coded and the other two were phase-encoded. High-resolution images wer e 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 verif ied by comparison to quantitative STEAM-localized and nonlocalized spe ctra that used total creatine as an internal concentration reference. Additionally, quantitatively accurate behavior of the SLIM and GSLIM t echniques as applied to data sets of low signal-to-noise ratio and to macroscopically heterogeneous objects was verified using simulations a nd real muscle lactate data sets with known heterogeneity.