Optimization of the CT component of SPECT-CT and establishment of local CT diagnostic reference levels for clinical practice.

Abstract

The aim of this study was to perform a process of optimization and establish local diagnostic reference levels (DRLs) for the computed tomography (CT) component of single-photon emission computed tomography (SPECT)-CT imaging, for use in clinical practice. A multidisciplinary group defined categories for the clinical purpose of the CT component of local SPECT-CT examinations. Each of the examinations were assigned a category, and optimization of acquisition and reconstruction parameters was performed to achieve the required image quality. Dose data were collated for 754 SPECT-CT scans performed on three systems over 10 months. The third quartile values for volume CT dose index and dose length product were calculated and established as local DRLs. Four categories of CT examinations were defined: attenuation correction; localization and attenuation correction; localization, characterization and attenuation correction; and diagnostic and attenuation correction. Local DRLs were established for 11 examinations. Reference was made to the proposed national DRLs set by a recent UK survey. This work describes a process of optimization and the creation of practical and effective local DRLs. These can be used in local audit of practice. In future, improved descriptors and standardization of SPECT-CT use would allow more practicable UK national DRLs to be created.