Random correction using singles count rates for DOI Positron Emission Mammography

With the aim of realizing the early diagnosis of breast cancer, we are promoting the research and development of a high-resolution Positron Emission Mammography (PEM). In order to obtain both high resolution and high sensitivity, this scanner uses for-layer DOI (depth of interaction) detectors consisting of small crystals being positioned close to the breast Since the total number of crystals in the scanner is extremely large and it is predicted that the total number of LORs is greater than the total number of events, a list-mode iterative image reconstruction method is required. Furthermore, a random correction method based on singles counting is beneficial for reducing statistical noise in randoms estimation at each LOR. However, an extremely large number of counters are required to count single events for each crystal. We also developed a random correction method calculating the count for each crystal. This method makes it possible to reduce the number of counters. We evaluated the efficacy of this technique incorporated in a list-mode iterative reconstruction using simulation data. Results demonstrated that random correction using conventional delayed coincidence method does not work well for the list-mode iterative reconstruction having an extremely large number of LORs, whereas random correction using singles count rates is effective for improving the image quality.