Title

Fluorine-18 Production for PET and an Investigation of the Fluorine-18(p,alpha)Oxygen-15 Reaction with a Radioactive Beam

Document Type

Dissertation

Publication Date

1995

Department

Physics and Astronomy

Abstract

Improved methods for the production of ^{18}F have been developed. The isotope, a beta^{+} emitter with a 110 min half-life, serves a vital role in positron emission tomography (PET), and more recently has become important in the emerging field of a radioactive beam development for nuclear reaction studies. Aside from increasing some PET radiopharmaceutical yields by factors of 2-20, the present work made possible a factor of 10 ^3-10^4 improvement in ^{18}F ion beam intensity over previously published methods. ^{18}F production targetry was developed for an 11.4 MeV, 6-8 mm FWHM, 50 muA proton beam from the UW cyclotron. Nucleophilic aqueous (^ {18}F) fluoride is produced via the ^{18}O(p,n)^ {18}F reaction on an enriched ( ^{18}O) water target. The target yield is (80 +/- 15)% of the theoretical maximum for beam currents up to 40 muA, with the highest yield to date of 70 GBq. Gas targets for the production of electrophilic (^ {18}F] F_2 were developed with a saturation bombardment yield of 3.10 +/- 0.40 GBq/muA for beam currents up to 45 muA, and a maximum yield to date of 45.5 GBq. The ^{18} F in either form has important applications in the labeling of PET radiopharmaceuticals, and the applicability of each to radioactive beam technology has been investigated. An ^{18}F ion beam was generated by a dual-accelerator method incorporating off-line chemical separation. ^ {18}F was produced on the UW radioisotope production cyclotron, then delivered to Argonne National Laboratory (ANL) for beam formation on the tandem accelerator on ATLAS. An average ^{18}F ^{-} beam intensity of 1ppA was achieved from a cesium vapor, sputter negative ion source (SNICS) with a peak intensity of 4.5 ppA. This was sufficient to allow direct measurements of the ^{18}F(p,alpha) ^{15}O reaction cross section at energies of astrophysical interest. Cyclotron targetry studies, radioactive beam production techniques and results from the ^{18 }F(p,alpha)^ {15}O experiment are presented.

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