A CT Scanner Using Coincidence Techniques

Abstract

A CT scanner has been designed which uses gamma rays produced by positron annihilation. A low-activity 22Na source produces the positrons, which, when they annihilate, create 0.511 MeV gamma rays travelling in opposite directions. These gamma rays can be used to image an object using NaI detectors that are collinear with the source. Requiring a coincidence between the detectors reduces background. LabVIEW software counted the number of gamma ray coincidences and translated and rotated a robotic table, allowing the attenuation to be measured along multiple beam paths through the object. Ultimately, the attenuation data can be used to reconstruct an image of the object being observed.