The aim of this project is to design, construct and test a prototype MRI-compatible PET scanner. Specifically, we aim to create a PET scanner insert that can be placed inside the bore of an MRI scanner (a 3T GE wholebody scanner in our case)to allow the imaging of animals (rats and larger sized animals up to a rabbit). Our concept is to base the PET insert on robust technologies that will not require lengthy and expensive development so that we can rapidly and efficiently explore the potential value of simultaneous MRI and PET scanning. Therefore, our MRI-compatible PET scanner consists of arrays of pixelated scintillator (LSO) optically coupled to position-sensitive photomultiplier tubes (PSPMTs) via fiber optic lightguides. Hamamatsu H8500 PSPMTs are resistant to signal degradation caused by magnetic effects due to their relatively short dynode chain. For the prototype only two detector heads were constructed.

Picture showing the two detector heads.

The data were stored inlist mode format and reconstructed using a limited angle MLEM algorithm. To test the prototype, a disk containing five hollow right cylinders (2mm, 4mm, 6mm, 8mm and 10mm in diameter and 10mm long) filled with water containing 18F (5mCi/ml, 185kBq/ml) (Figure 4). PET imaging was performed over a 600s period.  A Fast Spin Echo MRI scan was simultaneously acquired to produce the images shown below. The image sets were fused manually.

A) B) C)

Simultaneously-acquired images acquired from the MRI-compatible PET scanner. A) MRI image of the disk, B) PET image of the disk and C) the fused MRI-PET image of the disk.

Work continues on improving both the PET scanner and MRI receiver coil. Our goal is to create a full PET ring incorporated into an MRI coil for small animal imaging applications.

Recent MRI-PET Presentation from ITBS '05 in Milos, Greece