Ultra-high-resolution CCD-based gamma detection

Abstract

For the development and improvement of multi-pinhole SPECT systems, high-resolution gamma cameras can be essential. Electron-multiplying charge-coupled devices (EMCCDs) have a high resolution and sensitivity and therefore can be extremely useful for application in photon-counting scintillation gamma cameras. The scintillation crystal captures the gamma photons and converts their energy into (visible) light photons, which are detected by the EMCCD. A very low readout noise and a high sensitivity (over 90% for the visible spectrum) enable these devices to detect individual gamma interactions in the crystal. Algorithms have been developed to analyze the EMCCD images for the presence of the scintillation events and provide estimates of their position and energy content. The first photon-counting gamma camera based on EMCCDs was demonstrated in our group in 2005. Subsequently, during the course of this PhD project all elements of this gamma camera have been investigated and improved. This thesis will introduce the essential components of a CCD-based gamma camera, and subsequent chapters demonstrate improvements that have been implemented. These improvements range from the gamma photon-detection algorithm, the readout mode of the CCD, the optical coupling between scintillator and CCD, the scintillator material itself to the inclusion of side detectors for a priori indication of the number of interactions in the scintillation crystal. The thesis concludes with some future investigations and prospects.