Optimization of a compact medical gamma camera

Abstract

A detailed model of a compact gamma camera for applications in small animal SPECT has been developed using the ANTS2 simulation package. The predictive power of this model was demonstrated by comparing the simulated and experimentally determined light response functions (LRFs) of the prototype of the camera, which demonstrated remarkable similarity. Additionally, the validity of the model was confirmed by a very accurate reconstruction of the experimental event positions using the LRFs calculated from the simulated data. An optimization study was performed on the lightguide thickness for several configurations. It was shown that the optimal configuration of the detector has a diffuse reflector coupled to the back plane of the scintillator. It was also shown that it is beneficial to cover the side walls of the scintillator and the lightguide with an optical grease and a light absorbing layer. For this configuration, the optimal thickness of the lightguide was found to be 0.5 mm. The optimized camera spatial resolution was shown to be close to 0.5 mm, the maximum position reconstruction bias of 0.5 mm and the useful field of view of 28 mm × 28 mm (87 % of the crystal area).

Foi desenvolvido um modelo detalhado duma cˆamera gama compacta, para uso em SPECT para pequenos animais, atrav´es do uso do pacote de simula¸c˜oes ANTS2. O poder preditivo deste modelo foi demonstrado, comparando as fun¸c˜oes de resposta de luz (LRF) simuladas e as determinadas experimentalmente, que mostraram uma semelhan¸ca not´avel. Mais ainda, a validade do modelo foi confirmada por uma reconstru¸c˜ao muito precisa das posi¸c˜oes dos eventos experimentais, usando as LRFs calculadas atrav´es das simula¸c˜oes. Um estudo de otimiza¸c˜ao foi realizado sobre a espessura do guia de luz para v´arias configura¸c˜oes. Mostrou-se que a configura¸c˜ao ´otima do detetor tem um refletor difuso acoplado ao plano inferior do cintilador. Tamb´em se mostrou que ´e ben´efico cobrir os lados do cintilador e do guia de luz com ´oleo para acoplamento ´otico, e uma camada que absorve luz. Para esta configura¸c˜ao, a espessura ´otima do guia de luz encontrada foi 0.5 mm. A resolu¸c˜ao espacial da cˆamera gama otimizada est´a pr´oxima de 0.5 mm, e o campo de vis˜ao ´util ´e de 28 mm × 28 mm (87 % da ´area do cristal).