SBIR-STTR Award

Positron Emission Tomography (PET) is a metabolic imaging modality used to diagnose, stage, and restage seven Medicare-reimbursed cancer types. Currently ninty-six US cyclotrons proton-bombard stable enriched O-18 water, producing F-18 fluoride ion to synthesize F-18 fluorodeoxyglucose (FDG) used in 350,000 PET scans per year. Our goal is to significantly lower the cost of FDG and thereby lower the cost of PET scans by about 10%. CTI, EBCO, GE, and IBA cyclotrons (10-20 MeV) are capable of twice the beam power that can be dissipated by their targets. We seek to demonstrate feasibility of our thermosyphon target invention that may have the potential to double F-18 production and fully realize cyclotron potential. The thermosyphon beam and condenser volumes are loaded full of target water, sealed at the top, and run with beam while pressurized at the bottom with 30 atm He. This results in a heat transfer geometry much superior to conventional targets, which load partially and seal at the bottom, leaving a reflux void to be pressurized at the top. The thermosyphon self-regulates, moving liquid (displaced by thermal expansion and condenser steam) in and out the bottom port. The condenser steam space is in proportion to the beam power until beam strike liquid is invaded at the upper power limit. Foreign gas molecules impeding vapor transport are avoided. Aim 1 is demonstrating reliability of a new production thermosyphon target by running at Duke University Medical Center, four days a week for one month to support FDG synthesis for clinical PET and PET/CT scanning of 15-20 patients/day (beams at or above 30 microamps and F-18 yields at or above 70% theoretical). Duke F-18 production is predicted to improve from the current 600 mCi/hr to 2000 mCi/hr with the new thermosyphon target. Aim 2 is designing beta-test targets for cyclotrons capable of long runs at 1.0-1.5 kW beam power, namely a CS-15 (15 MeV, 10mm beam) at Anchorage, AK, and a domestic GE PETrace (16 MeV, 15mm beam). Aim 3 is fabrication and initial beam testing of beta-test targets at the two sites. Collaborators will cost-share fabrication, retaining possession in exchange for sharing operating experience and publication authorship. Phase II experiments will lead to a commercial product by measuring F-18 yields up to the power limit, and optimizing target depth and condenser geometry to minimize 0-18 water use.

Thesaurus Terms:
deoxyglucose, particle accelerator, positron emission tomography, technology /technique development high energy particle, thermodynamics

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%