Purpose: To develop a combined SPECT/CT based on a conventional gamma camera with the following design goals: (i) the subject is scanned on the same bed without moving between SPECT and CT scans, (ii) maintenance of full diagnostic utility of both scanners, (iii) a minimal equipment footprint which is adaptable to different site configurations, (iv) a modular design so that either scanner can be upgraded without impacting the other scanner and (v) cost-effectiveness.
Methods: A Philips SKYLight gamma camera was combined with a single-slice helical CT. The CT bed has been modified by mounting on wheels and is attached to a track in the floor when required. The CT bed is used for both the CT and the SPECT scans. The CT bed is parked outside the SKYLight's active area when not required. The CT data are used for anatomical localisation, attenuation correction and definition of anatomical boundaries (e.g. lobar boundaries in the lungs).
Results: The combined SPECT/CT system is installed in a 6.2 mx4.6 m room. The CT can scan up to 1.3 m of the subject, which is usually sufficient for registration with the SPECT scan. More than 200 subjects have had SPECT/CT scans in the first year of operation. Initially, the main outcome has been improved confidence of localisation of abnormalities. Attenuation correction for all relevant radionuclides has been implemented.
Conclusion: We have developed a combined SPECT/CT using a novel approach based on a low-cost CT scanner. The design is compact, is readily upgradeable and does not compromise either machine's diagnostic or functional capabilities.