Late effects of X irradiation on regulation of cerebral blood flow after whole-brain exposure in rats.

Hemodynamic parameters such as total cerebral blood volume (total CBV), cerebral parenchymal blood volume (CBV), cerebral blood flow (CBF) and cerebral blood velocity index were measured in rats 6, 12 and 18 months after single exposures of brain to 5, 10, 15 and 20 Gy X rays for total CBV, CBF and blood velocity index, and only 20 Gy for CBV. Total CBV and blood velocity index were determined by a noninvasive blood dilution method using [99mTc]pertechnetate and CBF by [131I]iodoantipyrine brain extraction. The CBV was obtained from both parenchymal plasma and erythrocyte volumes measured in isolated brain by 125I-labeled serum albumin and 51Cr-labeled erythrocytes, respectively.

Induced response to hypercapnia in the two-compartment total cerebral blood volume: influence on brain vascular reserve and flow efficiency.

This study was undertaken to investigate the mechanisms of CBF increase as induced by hypercapnia. It was achieved in anesthetized rats by determining total cerebral blood volume (TCBV), parenchymal blood (CBV), plasma (CPV), erythrocyte (CEV) volumes and cerebral hematocrit (CHct) as well as CBF at about 40, 60, and 80 mm Hg PaCO2. TCBV was measured by a noninvasive blood dilution method using [99mTc]pertechnetate.

Technetium-99m-pertechnetate as a whole blood marker for brain perfusion studies.

Unlabelled: In the brain, diffusible 99mTc-pertechnetate behaves as an intravascular indicator because it is confined within the circulation by the blood-brain barrier, allowing its use for noninvasive dynamic evaluation of cerebral circulation. For this application 99mTc has often been claimed to be a plasma marker. This study examines the validity of such a claim which has not yet been proven in vivo.

Total cerebral blood volume calculated from a model of [99mTc]pertechnetate distribution in the head.

A method for calculation of the blood volume from the internal carotid and vertebral arteries to the internal jugular veins [total cerebral blood volume (TCBV)] was validated. This was achieved noninvasively in anesthetized rats from the time-activity curve recorded over the head after [99mTc]pertechnetate (Tc) intravenous bolus injection. Tc had the advantage over many other tracers in that it rapidly and evenly distributed in blood cells and plasma.

[Long-term course of the cerebral circulatory function after brain irradiation in rats].

Long-term evolution of radioisotope indices, evaluating respectively the cerebral blood flow (CBF), the cerebral blood volume (CBV) and the cephalic specific distribution space of iodoantipyrine (delta IAP) of rat, was studied after brain irradiation at 20 Gy. Radioinduced hemodynamic alterations evidenced by this approach are biphasic and support the prominent role of circulation impairment in the genesis of delayed brain radionecrosis.