Physics of pure and non-pure positron emitters for PET: a review and a discussion

Abstract

With the increased interest in new PET tracers, gene-targeted therapy, immunoPET, and theranostics, other radioisotopes will be increasingly used in clinical PET scanners, in addition to ¹⁸F. Some of the most interesting radioisotopes with prospective use in the new fields are not pure short-range β ⁺ emitters but can be associated with gamma emissions in coincidence with the annihilation radiation (prompt gamma), gamma-gamma cascades, intense Bremsstrahlung radiation, high-energy positrons that may escape out of the patient skin, and high-energy gamma rays that result in some e ⁺/ e ⁻ pair production. The high level of sophistication in data correction and excellent quantitative accuracy that has been reached for ¹⁸F in recent years can be questioned by these effects. In this work, we review the physics and the scientific literature and evaluate the effect of these additional phenomena on the PET data for each of a series of radioisotopes: ¹¹C, ¹³N, ¹⁵O, ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, ⁷⁶Br, ⁸²Rb, ⁸⁶Y, ⁸⁹Zr, ⁹⁰Y, and ¹²⁴I. In particular, we discuss the present complications arising from the prompt gammas, and we review the scientific literature on prompt gamma correction. For some of the radioisotopes considered in this work, prompt gamma correction is definitely needed to assure acceptable image quality, and several approaches have been proposed in recent years. Bremsstrahlung photons and ¹⁷⁶Lu background were also evaluated.

Electronic supplementary material

The online version of this article (doi:10.1186/s40658-016-0144-5) contains supplementary material, which is available to authorized users.