Basic evaluation of three-dimensional position sensitive CdTe detector unit for clinical use of ultra-high resolution human PET scanner

We develop ultra-high resolution human PET scanner with the world's first resolution of less than 1 mm, which is used CdTe type semiconductor detectors. The aim of this study is that we develop three-dimensional position sensitive CdTe detector units which construct PET scanner, and evaluate basic performance of this scanner. Here we report about progress and outcome of its development. As the detector of our scanner, we developed position sensitive CdTe detectors (2D-PSD) two-dimensional . It can acquire interaction position inside the detector with positional resolution of 1.2 mm. By densely stacking 2D-PSD and subsequent circuits (Amplifiers, ADC, and other processing circuits), we developed three-dimensional position sensitive CdTe detector units. By placing these detector units with shape of decagon, we constructed PET gantry. In order to determine the operating conditions of the scanner, we performed evaluation and improvement of each detector unit. We confirmed high performance of each detector unit from their results, but we found out some of detectors indicate low performance and they need more improvement. Also we could determine the operating conditions (Setting values of bias voltage and each signal processing) to detectors from their results. For polarization phenomena of CdTe detector, we developed a bias reset system and decided its operating condition by experimental results. Next we evaluated the basic performance of the scanner.We moved a point source three directions in the field of view, and we evaluated basic spatial resolution. Finally we performed some phantom measurements, and we could obtain reconstruction images of their phantoms. By this research, we could forward development of the scanner to the stage of phantom study. However improvement of detector performance is a significant issue in the future. We will continue to evaluate performance of the scanner for clinical use.