Random correction for positron emission tomography using singles count rates

To obtain quantitative images in PET (Positron Emission Tomography) the correction for randomly occurring coincidences is an important step prior to reconstruction. Especially in 3D mode, random coincidences contribute considerably to all measured events. Tomographs with more open geometries and extended field of view (FOV) are particularly prone to random coincidences. Therefore efforts are made to develop methods for an estimation of their contributions as exact as possible and subtract them from the measured signal. A new random correction method has been developed and investigated. The estimation of random coincidences was done by using singles count rates of detector ensembles. This approach does not need a separate random measurement in a delayed coincidence window (standard technique) and thus it should relieve the load on the coincidence controller. More true coincidences could be recorded this way. The inferior statistical quality of the random measurements compared to the singles measurements is a further stimulus to utilize singles for the estimation. The performance of the new method has been compared with the current standard technique and its benefits have been quantified in a range of imaging situations. It has been demonstrated that the use of the new algorithm should lead to significant gains in performance.