Photonuclear target systems for producing clinically useful quantities of 11C using an electron linear accelerator

Described in this paper are what we believe to be the first practical photonuclear target systems for production of 11C containing CO and CO2 using bremsstrahlung produced from an electron linear accelerator similar to certain radiotherapy accelerators. This is a continuation of work reported earlier concerning a similar target system presently being used for production of 15O-O2. The 11C producing systems utilized liquid carbon dioxide, liquid cyclohexane, and liquid glacial acetic acid target materials. The carbon dioxide and glacial acetic acid target materials produced principally a 11C-CO product material. The cyclohexane target material produced a 11C-hydrocarbon product which was then oxidized to CO2. Target activity yields for these systems, normalized to a 20-cm-long by 10-cm-diam target chamber irradiated in a bremsstrahlung field produced by a 26-MeV, 100-microA electron beam, were 1.9 X 10(8) Bq (5 mCi) at 7.4 X 10(8) Bq g-1 (20 mCi g-1) for carbon dioxide, 1.4 X 10(8) Bq (3.8 mCi) at 3.7 X 10(10) Bq g-1 (1 Ci g-1) for cyclohexane, and 7.4 X 10(8) Bq (20 mCi) at 3.7 X 10(10) Bq g-1 (1 Ci g-1) for glacial acetic acid.