J Houseman | PubMed Health

PubMed1992

Perfusion and diffusion MR imaging.

Diffusion-weighted images of the rat brain were obtained using the pulsed-gradient spin-echo method. An attempt was made to extract perfusion-related parameters from signal intensity data taken from the caudate-putamen region of the images, by using a nonlinear least-squares calculation to fit the Le Bihan biexponential expression (Le Bihan et al., Radiology, 168, 497 (1988)) to the data. The perfusion-related parameters could not be obtained with sufficient accuracy to be useful, although the perfusion-weighted images appear to contain meaningful qualitative information. An analysis of the perfusion model is presented and shows why the Le Bihan pseudo-diffusion coefficient is particularly difficult to measure with reasonable accuracy.

Animals↗

PubMed1985

Retinal blood flow in the cat following periods of light and darkness.

Estimates of flow velocity in retinal arterioles of seven cat eyes were obtained using high-speed cine Indocyanine Green absorption angiography in the near-infra-red waveband, following alternate 30 min periods of light and darkness. Simultaneous estimates of vessel calibre were obtained by micrometry of the cine image. Comparisons of values obtained after periods of light adaptation with the preceeding and subsequent periods of darkness show no significant changes in vessel calibre (at P greater than 0.95 level, confidence limits +/- 17% of the mean) while three of 14 comparisons show significant but inconsistent changes in linear flow velocity (at P greater than 0.95 level, confidence limits +/- 22% of the mean). A significant decrease (41%) in b-wave amplitude was seen in six of seven experiments after dark adaptation subsequent to exposure to light for a total of 60 min.

Animals↗