title: Washout rate in rat brain irradiated by a (11)C beam after acetazolamide loading using a small single-ring OpenPET prototype.
abstract: In dose verification techniques of particle therapies based on in-beam positron emission tomography (PET), the causes of washout of positron emitters by physiological effects should be clarified to correct washout for accurate verification. As well, the quantitative washout rate has a potential usefulness as a diagnostic index which should be explored. Therefore, we measured washout rates of rat brain after vasodilator acetazolamide loading to investigate the possible effects of blood flow on washout. Six rat brains were irradiated by a radioisotope (11)C beam and time activity curves on the whole brains were obtained with a small single-ring OpenPET prototype. Then, washout rates were calculated with the Mizuno model, where two washout rates (k 2m and k 2s ) were assumed, and a two-compartment model including efflux from tissue to blood (k 2) and influx (k 3) and efflux (k 4) between the two tissue compartments. Before the irradiations, we used laser-Doppler flowmetry to confirm that acetazolamide increased cerebral blood flow (CBF) of a rat. We compared means of k 2m , k 2s and k 2, k 3 and k 4 without acetazolamide loading (Rest) and with acetazolamide loading (ACZ). For all k values, ACZ values were lower than Rest values. In other words, though CBF increased, washout rates were decreased. This may be attributed to the implanted (11)C reacting to form (11)CO2. Because acetazolamide increased the concentration of CO2 in brain, suppressed diffusion of (11)CO2 and decomposition of (11)CO2 into ions were prevented.
authors: Yoshiyuki
authors: Y
authors: Hirano
authors: Hiroyuki
authors: H
authors: Takuwa
authors: Eiji
authors: E
authors: Yoshida
authors: Fumihiko
authors: F
authors: Nishikido
authors: Yasunori
authors: Y
authors: Nakajima
authors: Hidekatsu
authors: H
authors: Wakizaka
authors: Taiga
authors: T
authors: Yamaya
mesh_terms: D000086:Acetazolamide / Q000378:metabolism*; D000818:Animals; D000927:Anticonvulsants / Q000378:metabolism; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology; D006439:Hemodynamics; D017078:Laser-Doppler Flowmetry; D008297:Male; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D051381:Rats
chemical_list: D000927:Anticonvulsants; D002250:Carbon Radioisotopes; D000086:Acetazolamide