Performance evaluation of a new LSO high resolution research tomograph-HRRT

In order to improve the capability for investigating the living human brain using positron emission tomography with regard to blood flow, metabolism and receptor characteristics for small structures such as cortical sublayers and nuclei, the spatial resolution has to be improved relative to what is available today. A spatial resolution of 2 mm or less in all three dimensions may be necessary to reach these research goals. In order to meet this goal a new next generation high resolution 3D-only LSO brain PET has been developed at CTI. The HRRT (High Resolution Research Tomograph) is not only the first LSO PET for human studies it is also the first PET with full DOI capability over an extended FOV. The HRRT has been delivered to the MPI Cologne in February 1999 and is presently being optimized in terms of energy discrimination, crystal positioning, coincidence timing and PSD to achieve optimal system performance with respect to resolution, count rate efficiency and scatter. The panel detector setup with its new setup challenges is still under development and investigations. First evaluation measurements are presently obtained. The measurements promise an excellent high resolution performance with a high count rate capability of the HRRT. The high random rates and the SF fraction measurements underline the necessity for a short coincidence time window and an improved energy resolution for such an in the images reveal a not yet optimized system setup and reconstruction parameters. The authors believe the results demonstrate the high capability of the new brain tomograph and justify the excitement for the first LSO tomograph with DOI capability for human brain investigations and the new scintillator LSO, superior for coincidence timing and energy resolution.