Performance evaluation of a parallel-hole collimated detector module for animal SPECT imaging

We have built and investigated a detector module for animal SPECT imaging, especially for use in large field of view (FOV) conditions. The module consists of a PMT-based detector and a parallel-hole collimator with an effective area of 80 mm × 80 mm. The detector is composed of a NaI scintillation crystal array coupled to four H8500 position sensitive photomultiplier tubes (PS-PMT). The intrinsic energy resolution of the detector is 11.5% at 140 keV on average. The planar spatial resolution of the module changes from 2.2 mm to 5.1 mm at different source-to-collimator distances with an unchanged sensitivity of about 34cps/MBq. Additionally, the SPECT Micro Deluxe Phantom imaging was performed with a radius of rotation (ROR) of 40 mm. Using the FBP reconstruction algorithm, a high performance image was obtained, indicating the feasibility of this detector module.     

第五届中德色谱报告会在大连召开

由中国科学院大连化学物理研究所、国家色谱研究分析中心承办的第五届中德色谱报告会于 1 999年 1 2月 2日～ 6日在大连召开。著名色谱学家Ｅ Ｂａｙｅｒ教授、Ｈ Ｅｎｇｅｌｈａｒｄｔ教授、Ｗ Ｅｎｇｅｗａｔｄ教授、卢佩章院士、陆婉珍院士、徐晓白院士等中外学者及国内一批杰出青年学者分别在大会上作了报告。大会共发表了 33篇论文 ,并就分离科学方面的专题进行了深入的讨论。首届中德色谱报告会于 1 981年在大连召开 ,之后分别在中德两国各举办过两届。这对加强两国的学术交流 ,促进双方研究人员在分析化学领域的合作起到了积极的推…     

Performance evaluation of CsI screens for X-ray imaging

Cs I film has been one of the most extensively used scintillators for indirect X-ray imaging because of its needle-like micro-structure. The purpose of this paper is to investigate the imaging performance of Cs I screen as a function of thickness and radiation quality. Four multilayer scintillation screens with microcolumnar Cs I:Tl film(thicknesses of 50 μm, 100 μm, 200 μm and 300 μm) included were prepared and coupled to an optical imaging sensor. The modulation transfer function(MTF), normalized noise power spectrum(NNPS) and detective quantum efficiency(DQE) of these screens were evaluated based on the standard IEC 62220-1, and the results indicated that,in the medium spatial frequency range(1–6 lp/mm), the MTF of Cs I screens with the same thickness was lower when the incident X-ray photon energy was higher, possibly owing to scattering and K-fluorescence re-absorption effects. The NNPS in the higher spatial frequency range(above 8 lp/mm) is dominated by stochastic noise while the entrance surface air Kerma(ESAK) decreases. For 100 μm, 200 μm and 300 μm thick Cs I screens, the DQE under RQA7 and RQA9 is lower than that under RQA3 and RQA5 due to low absorption efficiency.     

Preliminary study of depth of interaction measurement for a PET detector

In this work we studied the feasibility of detecting the depth of interaction (DOI) with two layers of crystal arrays of LYSO and BGO scintillators coupled to a position-sensitive photomultiplier tube (PS-PMT) R8900-C12. A front-end electronics was designed, with which we got different pulse shapes for different crystals to obtain depth information. With the double integration method, we got the DOI histogram of a divided integration ratio of two crystals as the standard to determine the layer-of-interaction. The DOI accuracy, measured by scanning a ²²Na slit source along the side of the module, was 98% for the LYSO layer and 95% for the BGO layer. The energy resolution at 511keV was 13.1% for LYSO and 17.1% for BGO. We obtained good crystal separation in 2D position histograms of both layers. These results could be useful in the manufacture of PET scanners with high spatial resolutions.