Determining timing resolution from TOF-PET emission data

TOF resolution is known to degrade with increasing count rate. During TOF-PET reconstruction the timing resolution of the data is used as an input for the reconstruction algorithm. The effect of the kernel width on the reconstruction was investigated in this paper. We looked at contrast recovery and background uniformity. Noise free simulation data were used together with high count measured TOF-PET data. The results clearly indicate that only the correct kernel should be used to reconstruct the data. Other kernels result in wrong contrast and less uniform background regions. Therefore it would be very useful to be able to estimate the TOF kernel from the data themselves. It is first shown that the likelihood reaches a maximum at the correct timing resolution. Then a method to estimate the kernel from both a non-TOF reconstruction and the measured TOF data is described. The determination of the timing resolution is performed with an iterative method using the non-TOF MLEM reconstruction and Richardson-Lucy deconvolution.