Measurement of regional cerebral blood flow in cat brain using intracarotid ²H₂O and ²H NMR imaging

Abstract

Cerebral blood flow (CBF) was measured in cat brain in vivo at 2.7 T using 2H NMR to monitor the washout of deuterated saline injected into both carotid arteries via the lingual arteries. In anesthetized cats, global CBF varied directly with PaCO2 over a range of 20-50 mm Hg, and the corresponding global CBF values ranged from 25 to 125 ml.100 g-1.min-1. Regional CBF was measured in a 1-cm axial section of cat brain using intracarotid deuterated saline and gradient-echo 2H NMR imaging. Blood flow images with a maximum pixel resolution of 0.3 x 0.3 x 1.0 cm were generated from the deuterium signal washout at each pixel. Image derived values for CBF agreed well with other determinations, and decreased significantly with hypocapnia.

Indirect 17O‐magnetic resonance imaging of cerebral blood flow in the rat

“…Substituting Eq. [2] into Eq. [1] and taking the ratio of signal intensities obtained at h and l , i.e., S h and S l , respectively, one obtains an equation which may be rearranged to elucidate the following relationship:…”

“…MRI, because of its noninvasive nature and high anatomical resolution, is being applied in a number of novel ways for determining CBF. One approach uses direct 2 H (1,2), 19 F (3-6), or 17 O (7-11) MR spectroscopy (MRS) or imaging to trace nonradioactive, exogenous markers (e.g., 2 H 2 O, CH 19 F 3 , and H 2 17 O) and quantify CBF from the time-dependent tracer concentration. While MRS offers superior tracer specificity and sensitivity, it has limited spatial resolution.…”

“…While MRS offers superior tracer specificity and sensitivity, it has limited spatial resolution. A problem with imaging 17 O or 2 H directly is that both nuclei have low gyromagnetic ratios and small natural abundances. As a result, direct 17 O or 2 H-MRI suffers from poor signal/noise ratio (SNR) and considerably lower spatial resolution than 1 H-MRI.…”

“…The primary objective of this study was to demonstrate the feasibility of indirect 17 O-MRI, specifically based on the proton T 1 -dispersion imaging approach, for high-resolution 1) quantitation of absolute H 2 17 O concentration, and 2) mapping of absolute CBF using exogenous H 2 17 O as a freely diffusible tracer. Furthermore, we demonstrate a strategy whereby absolute CBF mapping is achieved without having to transform the T 1 signal into absolute H 2 17 O tracer concentration.…”

“…Furthermore, we demonstrate a strategy whereby absolute CBF mapping is achieved without having to transform the T 1 signal into absolute H 2 17 O tracer concentration.…”