2D-sensitive hpxe gas proportional scintillation counter concept for nuclear medical imaging purposes

Abstract

The operation and first images of a high pressure xenon Gas Proportional Scintillation Counter (GPSC) are presented. In this setup, primary electrons produced by the absorption of Xor γ-rays in the gas medium drift to a region where the electric field is set to a value above the gas scintillation threshold, the scintillation region. The primary ionization signal is amplified through the electroluminescence produced along the electron drift in this region. A Micro-Hole and Strip Plate covered with CsI (CsI-MHSP) is used as the photosensor for the scintillation readout. The 2D capability of the CsI-MHSP photosensor is achieved by means of two orthogonal resistive lines interconnecting the strips patterned on both surfaces of the MHSP. The interaction position of the incident radiation can be obtained by determining the centroid of the photosensor area irradiated by the electroluminescence pulse. This centroid is obtained from the amplitude of the charge pulses collected at both ends of the resistive lines. Preliminary analyses of the first images obtained with electroluminescence signals at xenon pressures up to 3 bar indicate a position resolution capability of about 1.2 mm at 2.9 bar, for 59.6 keV γ-photons.

SPECT detectors: the Anger Camera and beyond

“…Although several different configurations have been investigated (Bolozdynya et al ., 1997; Tsyganov et al ., 2008; Azevedo et al ., 2011), gas-based detectors have not found widespread use in SPECT and will not be discussed further.…”

Development of a parallel-plate avalanche counter with optical readout (O-PPAC)

“…The wide range of applications that rely on the most advanced EL detectors include doublephase liquid noble gas time projection chamber (TPC) for rare event searches (e.g. dark matter [8,[13][14][15][16][17], neutrino physics [18][19][20][21], low energy X-rays [22,23], and nuclear medical imaging [24]). New technologies such as linear (APD) or Geiger (SiPM) Avalanche Photo-Diode [25], hybrid devices [26] and fast Charge-Couple Device CCD [27], are extremely sensitive and allow EL-based readout to deliver better signal-to-noise ratio and better energy resolution compared to the traditional charge-based detectors.…”

Pressure effects on the X-ray intrinsic position resolution in noble gases and mixtures

“…Experimental measurements have shown that the increase of gas pressure leads to an improving of the position resolution [2,7,8], however the measurement technique relies on detectors where the position resolution measured depends on the detector gain and on the electron diffusion in the gas. Thus, in order to decouple the position resolution from the detector gain, the intrinsic position resolution of pressurized pure noble gases (Ar and Xenon, in the pressures range 1-10 bar) was calculated, studied and compared with the available experimental data.…”

“…The most usual way to overcome this problem is to increase the gas pressure, thus increasing the number of gas atoms/molecules per unit volume. Also, the pressure increase will enhance the energy resolution and light production when, for instance, coupled to an electroluminescence-based readout [2][3][4]. It is expected that the pressure increase will reduce the electrons diffusion in the gas medium, which will in turn result in a better position resolution when compared to the value obtained at atmospheric pressure [5,6].…”

“…Experimental measurements have shown that the increase of gas pressure leads to an improvement of the position resolution [2,7,8], however the measurement technique relies on detectors for which the position resolution measured may be naturally limited in those conditions. The attainable detector signal-to-noise ratio (with gas gain usually decreasing at high pressure) and the diffusion of the ionization electrons are the two main such limiting effects [7,16].…”