Measurement of brain perfusion by volume‐localized NMR spectroscopy using inversion of arterial water spins: Accounting for transit time and cross‐relaxation

Abstract

The theoretical model for perfusion measurement by NMR using arterial labeling of endogenous water is extended to include the effects of transit time and cross-relaxation of tissue water with macromolecules. Water magnetization in rat brain is monitored using the STEAM method to simultaneously determine the transit time, magnetization transfer rate constant, and perfusion. The results show that the transit time in rat brain is quite short, and thus its effect on perfusion measurement is small. It is also demonstrated both theoretically and experimentally that the steady-state effects of cross-relaxation with macromolecules on perfusion measurement are accounted for by a proper control experiment.

Quantification of rodent cerebral blood flow (CBF) in normal and high flow states using pulsed arterial spin labeling magnetic resonance imaging

“…In a study by Sicard et al (31), administration of 5% CO 2 to spontaneously breathing, isoflurane-anesthetized animals resulted in a 25% increase of CBF with an average pCO 2 of 50 mm/Hg. A more pronounced increase in CBF was found in other studies with isoflurane (15), halothane (37,38), and ␣-chloralose (12). With a mean pCO 2 of 54.1 mm/Hg, our data are consistent with a 5% CBF change per mmHg CO 2 increase with invasive methods (39).…”

“…Mean dt values decreased by 39%. Previous studies have reported tran-sit delay decreases by 13% with a pCO 2 of 70 mmHg in tissue voxels (15), and 48% with a pCO 2 of 86 mmHg (37). In a study by Sicard et al (31), administration of 5% CO 2 to spontaneously breathing, isoflurane-anesthetized animals resulted in a 25% increase of CBF with an average pCO 2 of 50 mm/Hg.…”

Spoiled gradient‐echo as an arterial spin tagging technique for quick evaluation of local perfusion

“…of the AST pulse and before imaging (19,23). This time interval allows delivery of the tagged blood spins to tissue voxels in the imaging slice and also enables washout of the tagged blood from the proximal arteries.…”

Measurement of cerebral perfusion territories using arterial spin labelling

“…When a single labeling/imaging RF coil is used, the off-resonance RF pulse required for ASL saturates macromolecules in the brain, resulting in a large spatially dependent decrease of the signal intensity due to magnetization transfer (MT) effects (38). The original way to account for MT effects was to acquire a control image with RF power applied on a plane symmetrically opposed to the labeling plane (37,38), which limited data acquisition to a single slice centered between the labeling and control planes.…”

“…When a single labeling/imaging RF coil is used, the off-resonance RF pulse required for ASL saturates macromolecules in the brain, resulting in a large spatially dependent decrease of the signal intensity due to magnetization transfer (MT) effects (38). The original way to account for MT effects was to acquire a control image with RF power applied on a plane symmetrically opposed to the labeling plane (37,38), which limited data acquisition to a single slice centered between the labeling and control planes. While some methods were proposed to extend the coverage of both PASL and CASL to multiple slices (39)(40)(41), MT effects still imposed a few hard to overcome constraints, such as imaging slice orientation restricted to the labeling direction (39,40) and reduction of the effective degree of spin labeling (41).…”