Solid-State SPECT technology: fast and furious

Abstract

This traditionaldesign uses a thallium-doped sodium iodine crystalwhich scintillates in response to gamma photons, pro-ducing weak flash of light, coupled with a set ofphotomultiplier tubes which detect the fluorescent flash.A parallel-hole collimator filters the incident gammarays so that only those traveling approximately parallelto a specified direction are allowed through. This designof the conventional gamma camera suffers from severalmajor limitations, compromising its performance. Thephoton energy resolution is limited due to the physicalcharacteristics of the NaI crystal and photomultipliers,while the spatial resolution is reduced due to the geo-metric characteristics of the collimator and limitednumber of photomultipliers. The sensitivity of thecamera system is very low since the low-energy high-resolution collimator attenuates the overwhelmingmajority ([99.9%) of the incident photons. Thesetechnological limitations lead to relatively a largeamount of administered radiation doses, and/or pro-longed imaging time. Furthermore, the photomultipliertube technology results in a large, bulky camera head,requiring large laboratory space and dictating inconve-nient patient position.A major aim in nuclear cardiology to date has beento achieve reducing patient radiation exposure andimaging time, while improving image quality and thusdiagnostic precision. The use of dual-detector SPECTcameras resulted in 50% or greater reduction in imagingtime, and the use of iterative reconstruction algorithmswith resolution recovery provided additional reductionin acquisition time, without compromising resolution.