Investigating oxygen-14 water and carbon-10 carbon dioxide as cerebral blood flow tracers in PET.

摘要

Functional brain mapping with positron emission tomography (PET) is limited largely by exam time, mainly waiting between subsequent injections for the prior dose to decay. This time can be reduced by using a shorter-lived isotope than the commonly used oxygen-15 (beta+, 122 second half life). Two alternative isotopes have been developed. These isotopes, oxygen-14 (beta+, 2314 kev gamma, 71 second half life) and carbon-10 ((beta+, 719 kev gamma, 19 second half life), hold the promise of increasing study repetition rate by a factor of 2--5.; Production targetry for 10C and 14O were developed for an 11.4 MeV, 6--8 mm FWHM proton beam from the UW cyclotron. 14O is produced via the 14N(p,n)14O reaction in a 99.5% N2 0.5% O2 flow through target, and 10C is produced by bombarding enriched 10B 2O3 via the 10B(p.n)10C reaction. Extraction of the 10C from the boric oxide melt is strongly temperature dependent, and evidence is presented indicating that this extraction is greatly aided by convection. Both isotopes were converted to CO2 in high-speed flow-through chemistry, and the radiochemical purity of the final product was measured.; The dosimetry of these short lived blood flow tracers was calculated with computer simulation. Where possible the calculated results were compared to measured and calculated values in the literature, and show good agreement. This study shows that both 14O and 10C suffer dosimetrically from their gamma rays, but this is offset by their greater study repetition rates.; The effects of the prompt gamma rays of 14O and 10C on image degradation were explored on a variety of PET scanners, in both 2D and 3D phantom studies. These data show minimal effect in the final image quality. This is born out by human imaging, performed at the Rigshospitalet in Copenhagen, Denmark.