SPECT detectors: the Anger Camera and beyond

Abstract

The development of radiation detectors capable of delivering spatial information about gamma-ray interactions was one of the key enabling technologies for nuclear medicine imaging and, eventually, single-photon emission computed tomography (SPECT). The continuous NaI(Tl) scintillator crystal coupled to an array of photomultiplier tubes, almost universally referred to as the Anger Camera after its inventor, has long been the dominant SPECT detector system. Nevertheless, many alternative materials and configurations have been investigated over the years. Technological advances as well as the emerging importance of specialized applications, such as cardiac and preclinical imaging, have spurred innovation such that alternatives to the Anger Camera are now part of commercial imaging systems. Increased computing power has made it practical to apply advanced signal processing and estimation schemes to make better use of the information contained in the detector signals. In this review we discuss the key performance properties of SPECT detectors and survey developments in both scintillator and semiconductor detectors and their readouts with an eye toward some of the practical issues at least in part responsible for the continuing prevalence of the Anger Camera in the clinic.

Hybrid Imaging: Instrumentation and Data Processing

“…Most PET and SPECT systems are composed of pixelated scintillators to assign the interaction position of the gamma photon [74], although blocks made of continuous crystal have been proposed as well [75,76]. Table 3 lists some of the scintillators commonly used in CT, SPECT and PET detector systems together with their key properties [77][78][79][80][81]. New scintillator materials are being developed continuously.…”

“…Furthermore, with the use of highly granulated detectors high spatial, energy and time resolution can be achieved [88]. Table 5 summarizes important properties of some semiconductor materials used for medical imaging applications [80].…”

The state of the future is solid

“…[10][11][12][13][14][15][16] However, there was always an interest in the development of new imaging crystals to avoid the numerous problems that exist with sodium iodide-based detectors such as hydrophilicity, temperature instability, etc. [17][18][19][20][21] While a number of other crystal types were proposed to replace sodium iodide, cadmium zinc telluride (CZT) has emerged as a top contender in the field. While still expensive, it is anticipated that, in time, cameras using these new solid-state detectors will become more affordable for cardiac SPECT imaging.…”

“…Iterative reconstruction has been shown to be superior to filtered back projection, and most conventional cameras are now able to use these more advanced algorithms which enhance image contrast and reduce noise. [13][14][15][16][17] In summary, SPECT cameras using solid-state CZT detectors represent a significant advance in nuclear cardiology imaging. The study by Oldan et al is the first study to compare the real-life performance of this new technology and demonstrates equivalence with conventional cameras.…”

Ionizing Radiation in Medical Imaging and Efforts in Dose Optimization

“…Improvement in detectors such as the new cadmium-zinc-telluride detectors will facilitate higher speed/resolution gamma camera and reduce noise (Erlandsson et al, 2009). This equates to higher detector sensitivity, and the hope is that this will generally lead to less administered dose requirement over time (Peterson et al, 2011).…”