SIC: an intracerebral radiosensitive probe for in vivo neuropharmacology investigations in small laboratory animals: prototype design, characterization, and in vivo evaluation

Abstract

Several high-resolution tomographs dedicated to small animal imaging are presently under development. However, these devices are limited by two major drawbacks: their cost is high and they require animal anaesthesia and immobilization, thus restricting the scope of investigations. Therefore, we have developed SIC (French acronym for "Sonde IntraCérébrale") a low-cost beta microprobe for measuring local radioactivity in awake, freely moving animals. Besides good sensitivity, SIC offers the advantage of a high temporal resolution, a major asset for in vivo measurements of tracer kinetics. Furthermore, SIC can be readily combined with existing techniques such as electrophysiology, microdialysis, voltammetry and magnetic resonance imaging, providing simultaneous complementary information on cerebral function. We present here the design, manufacture, and evaluation of a SIC prototype. In vitro evaluation using a beaker filled with a homogenous aqueous solution of [ 18 F]-fluorodeoxyglucose ( 18 F-FDG) confirmed our Monte Carlo simulation results in terms of sensitivity and detection volume. Further in vivo studies on rats with two probes implanted in the brain validated the use of SIC to measure the local concentration of radio-labeled molecules in rat brain with a high temporal resolution.Index Terms-Beta detector, in vivo kinetics, intracerebral probe, positrons.

A positron-probe system for arterial input function quantification for positron emission tomography in humans

“…System dead time ͑2.5 s͒ was similar to that reported by Pain et al 28 and by Wollenweber et al 31 Because the system response did not reach a ceiling ͑the system did not saturate͒, it can be readily corrected to linear response over the range of radioactivity anticipated ͑R 2 = 0.999͒. Based on these data, this system can be used for accurately determining activity concentrations at least as high as 21.0 MBq/ ml.…”

“…This means that a measured energy spectrum of 15 O is quite different from that theoretically calculated by Champion and Loirec. 30 Moreover, our value is also about 18% above the average kinetic energy ͑492 keV͒ estimated by Monte Carlo simulation of Pain et al 28 using detection radius to detect 90% of positron particles emitted near the probe.…”

“…͑1͒ with observed and real count rates using least-squares fitting for the range between 92 000 and 5600 counts/ s ͑t =0 s−t = 550 s͒. The dead time was approximately 2.5 s which is similar to the SIC probe system of Pain et al 28 This dead time is adequate for biological kinetic measurement with concentrations up to 21 MBq/ ml. The decay curves of the ␤ + probe with and without dead time correction are shown in Fig.…”

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

“…The limited range of b-particles within biological tissues leads to a limited detection volume centered around the scintillating tip of the probe. Monte Carlo simulations demonstrated that for C-11 the distance required to detect 90% of the b-particles around the probe is 2.0 mm (Pain et al, 2002). The sensitivity of the used b-scintillator was in the range of 0.036 to 0.047 cps/kBq/cc.…”

Polyvinyltoluene scintillators for relative ion dosimetry: An investigation with Helium, Carbon and Neon beams

“…Most of these small sized dosimeters are devoted to conventional photon therapy, as those presented by Beddar et al, for use in stereotactic radiosurgery [5][6], or by Fontbonne et al for use in brachyterapy [7]. Pain et al have also presented a dosimeter allowing in vivo measurements of low dose β emission [8][9]. The potential use of plastic scintillators for the dosimetry in hadrontherapy has only been demonstrated for protons by Torissi [10].…”