SPECT/CT technology

Abstract

The continuous development of SPECT over the past 50 years has led to remarkably improved image quality and increased diagnostic confidence. The most influential developments include the realization of hybrid SPECT/CT devices, as well as the implementation of attenuation correction and iterative reconstruction techniques. These developments have led to a preference for SPECT/CT devices over SPECT-only systems and to the widespread adoption of the former, strengthening the role of SPECT/CT as the workhorse of nuclear medicine imaging. New trends in the ongoing development of SPECT/CT are quite diverse. For example, whole-body SPECT/CT images, consisting of acquisitions from multiple consecutive bed positions in the manner of PET/CT, are increasingly performed. Another recent advance has been the incorporation of additional information obtained from the CT images into the SPECT reconstruction, thereby allowing CT data to be used for more than just attenuation correction and image fusion. Additionally, in recent years, some interesting approaches in detector technology have found their way into commercial products. For example, some SPECT cameras dedicated to specific organs employ semiconductor detectors made of cadmium telluride or cadmium zinc telluride, which have been shown to increase the obtainable image quality by offering a higher sensitivity and energy resolution. Most important, the recent advent of quantitative SPECT/CT which, like PET, can quantify the amount of tracer in terms of Bq/mL or as a standardized uptake value, is a major innovation that will lead to increased diagnostic accuracy and confidence, especially in longitudinal studies and in the monitoring of treatment response. This article describes some of the physical and technical fundamentals of SPECT/CT and reviews established as well as experimental technical developments. It also introduces the aforementioned recent trends in the field of nuclear medicine imaging, such as specialized collimators, SPECT cameras for anatomical imaging (e.g. cerebral/cardiac imaging) and new detector technologies.