An MR Compatible LSO-PET Scanner for Molecular Imaging Studies

We present a detailed system description of an MR compatible PET scanner for small animal molecular imaging studies, which has recently been constructed. The system images a single slice and has an inner diameter 7.5cm. It consists of 4 concentric rings of 104 LSO crystals each with nominal dimensions of 2mm (tangential) by 3mm (axial) by 5mm (radial). The crystal ring is positioned at the centre of an MR scanner, and 3.5m long optical fibres transport the scintillation light to eight multi-channel PM tubes situated in a low field region in which they can function correctly. Position encoding boards convert the large number of signals from these multichannel photo-multiplier tubes to four position encoded signals. The electronics are standard NIM modules and can be housed in just two racks, to allow the system to be relocated easily for operation in a range of MR scanners. The signals are digitized on ADC cards in a PC and the raw data converted into a sinogram using an interpolation method prior to reconstruction. We present some preliminary results from the PET system. The system will now be fully evaluated and its performance assessed within the MR environment.