Quantitative Cerebral Blood Flow Measurements in the Rat Using a Beta-Probe and H₂¹⁵O

Abstract

Beta-probes are a relatively new tool for tracer kinetic studies in animals. They are highly suited to evaluate new positron emission tomography tracers or measure physiologic parameters at rest and after some kind of stimulation or intervention. In many of these experiments, the knowledge of CBF is highly important. Thus, the purpose of this study was to evaluate the method of CBF measurements using a beta-probe and H2 15O. CBF was measured in the barrel cortex of eight rats at baseline and after acetazolamide challenge. Trigeminal nerve stimulation was additionally performed in five animals. In each category, three injections of 250 to 300 MBq H2 15O were performed at 10-minute intervals. Data were analyzed using a standard one-tissue compartment model (K1 = CBF, k2 = CBF/p, where p is the partition coefficient). Values for K1 were 0.35 +/- 0.09, 0.58 +/- 0.16, and 0.49 +/- 0.03 mL x min(-1) x mL(-1) at rest, after acetazolamide challenge, and during trigeminal nerve stimulation, respectively. The corresponding values for k2 were 0.55 +/- 0.12, 0.94 +/- 0.16, and 0.85 +/- 0.12 min(-7), and for p were 0.64 +/- 0.05, 0.61 +/- 0.07, and 0.59 +/- 0.06. The standard deviation of the difference between two successive experiments, a measure for the reproducibility of the method, was 10.1%, 13.0%, and 5.7% for K1, k2, and p, respectively. In summary, beta-probes in conjunction with H2 15O allow the reproducible quantitative measurement of CBF, although some systematic underestimation seems to occur, probably because of partial volume effects.

Quantitative Evaluation of Cerebral Blood Flow and Oxygen Metabolism in Normal Anesthetized Rats: 15O-Labeled Gas Inhalation PET with MRI Fusion

“…In previous PET studies, a bolus injection of 15 O-labeled water ( 15 O-H 2 O) was used for quantitative measurement of the CBF; the reported CBF values ranged from 35 to 51 mL/100 g/min (6,8,20). Kobayashi et al reported a steadystate method consisting of a bolus injection followed by injection of 15 O-H 2 O at slowly increasing doses with a multiprogramming syringe pump (9).…”

“…For quantitative measurements, the radioactivity of the cardiac chambers has been measured (3). A b-probe was developed to directly measure the arterial input function, without any need for blood sampling (8). Furthermore, programmed injection devices have been developed to achieve steady-state radioactivity of the brain (9).…”

N-Acetylcysteine– and MK-801–Induced Changes in Glutamate Levels Do Not Affect In Vivo Binding of Metabotropic Glutamate 5 Receptor Radioligand 11C-ABP688 in Rat Brain

“…For the b-microprobe recordings, a Microscintillator twin-system (SwissTrace) was used together with 2 scintillator probes (0.5 mm) (22). The b-microprobe recorded the positrons (b1 particles) emitted by the radiotracer.…”

Stimulation-Induced Increases of Astrocytic Oxidative Metabolism in Rats and Humans Investigated with 1-11C-Acetate

“…The b-scintillator (Swisstrace, Zurich, Switzerland) has been described in detail earlier (Weber et al, 2003;Wyss et al, 2007). In short, it consists of a scintillation tip (Bicron, BF12, Newbury, OH, USA) with a length of 1 mm and a diameter of 0.25 mm attached to a high numerical aperture glass fiber.…”