Medical Physics Seminar – Monday, March 10, 2014
Radiometal Production Using Solution-Based Cyclotron Targets
Timothy R. DeGrado, PhD (guest of Dr. Weibo Cai)
Professor, Depts of Radiology, Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN
We are developing solution-based targets for radiometal production on medium energy cyclotrons. The solution target approach has reduced capital costs when compared with traditional solid targets and does not require solid target replating. We began our work using an off-the-shelf F-18 production target and investigated production of Zr-89 by the 89Y(p,n)89Zr reaction, taking advantage of the low cost of Y starting material and the “worst case scenario†long half-life of Zr-89. Unexpected happenings with high amounts of gas evolution from the target spawned creative mechanistic studies to find the culprit: mainly radiolysis of water, that was dependent on a host of factors, including the salt composition, concentration, and pH. Conditions were optimized for minimizing the gas evolution, and ~4 mCi Zr-89 could be produced in 2 h at 20 uA proton beam. We have extended this method for production of Ga-68, Zn-63 and Cu-64. Furthermore, we are developing our own target design with enhanced heat transfer and finding dramatically reduced gas evolution rates.