TOF Data Compression on High Time Resolution Clinical Scanner

The development of silicon photomultiplier (SiPM) based detectors resulted in significant improvement of time-of-flight (TOF) resolution in PET. The Siemens Biograph Vision PET/CT scanner has a time resolution below 250 ps. Raw histogrammed data are significantly increased in size due to the increased sampling in the TOF dimension. Due to the redundancy of TOF information, data can be further compressed without loss of resolution. Such compression consists of axial rebinning and azimuthal mashing. With a significantly reduced number of views and tilts, data are still suitable for TOF reconstruction. Data compression results in the modification of correction factors (mainly the normalization array construction and random smoothing procedure), since these factors became TOF dependent. Using a smaller number of azimuthal views requires modification of those commonly used on the Siemens scanner analytical reconstruction algorithm.The Biograph Vision PET/CT scanner uses significant azimuthal mashing (factor 8) and axial spanning (span 19). Normalization coefficient computing accommodates for high frequencies in the nearest neighbor interpolation in data compression without introducing image artifacts.The IQ phantom small sphere recovery and point source measurements across the field-of-view displayed a very minimal loss in resolution. Resolution phantom and patient scans visually reveal no difference in reconstructions between highly compressed and un-compressed data. The statistical reconstruction of TOF summed compressed data is still possible in the current approach to evaluate TOF vs non-TOF benefits.