THERMOSYPHON TARGETRY TO IMPROVE F-18 PET

DESCRIPTION (provided by applicant): The overall objective of the proposed work is to reduce the cost of accelerator produced F-18 radiopharmaceuticals used in Positron Emission Tomography (PET), a Medicare-reimbursed nuclear medicine metabolic imaging modality used to diagnose, stage, and restage ten cancer indications. Annual PET scans (350,000+) are rapidly increasing, but CMS reimbursement for PET scans is decreasing 23% from $1774 in 2004 to $1371 in 2005. Twenty percent of the total cost is the radiopharmaceutical dose of F-18 fluorodeoxy glucose (FDG). Sustaining growth in the use of PET will thus benefit from reducing the cost of producing FDG. The goal of this project is to lower cost per dose by a factor of two through the use of our invention called the thermosyphon target, which can remove twice as much proton beam heat as the one kilowatt limit of present target technology. Removing more heat allows full use of the available proton beam current in the installed base of PET cyclotrons, thus at least doubling the production of O-18(p,n)F-18 for FDG (feasibility established by Phase I prototype target experiments using the 27 MeV proton beam of the positive-ion Duke University PET Facility cyclotron). Two additional thermosyphon targets were designed and built in Phase I as preparation for testing to their thermal limits in Phase II at other accelerators (one with beam power of nine kilowatts). This proposed high power target engineering is breaking new ground, and Phase n research may have to address difficult technical problems not previously encountered. Phase II aim 1 is beam testing to determine the thermal limits of the prototypes built in Phase I for two negative-ion proton cyclotrons with energies of 16 and 30 MeV. Aim 2 is correlating test results with predictive thermohydraulic models to design improvements. Aim 3 is developing material science technology to coat high thermal conductivity target body materials (Cu, Ag) with chemically inert refractory metals (Ta, Nb), in order to accommodate high beam power while maintaining viable labeling chemistry. Aim 4 is developing efficient methods of recovering F-18 fluoride ion from thermosyphon designs. Aim 5 is applying results of the previous aims to build and test additional improved prototypes. Aim 6 is the design and demonstration of a reliable high-performance target system suitable for widespread commercial use. Aim 7 is applying the thermohydraulic models to determine performance envelopes to dictate target system designs for a variety of accelerators. The goal of Phase III is to make this technology available for retrofit to appropriate existing accelerators (currently estimated at 70) and for use by manufacturers of new cyclotrons, thus implementing cost reduction of F-18 FDG by a factor of two or more to reduce total PET scan costs about 10%.