SPECT/CT hybrid imaging; with which CT?

The aim of this study is to show the practical use of, and to discuss the rationale for, high-end computed tomography (CT) integrated with intrinsic low-resolution single-photon emission tomography (SPECT).

All examinations performed on three new SPECT/CT systems with diagnostic CT capabilities were recorded retrospectively. The use of CT was classified as low-dose, using the CT with restraint as to the tube current and radiation dose, or diagnostic, with an optimum use of the CT, using CT protocols as used in ordinary radiological practice. The number of low-dose CT was compared with the number of diagnostic CT examinations. The report is based on 436 patient examinations from three hospitals in Norway with recently installed SPECT/CT systems, the time of use varying from 6 months to 2 years. The examinations performed were myocardial perfusion (45%), various tumors (thyroid, parathyroid, neuroendocrine 37%), malignant skeletal disease (12%), brain perfusion (4%), sentinel nodes in breast cancer (1%) and gastrointestinal bleeding (1%).

Of the 436 patients, 431 had a low-dose CT for attenuation correction, anatomic localisation and, also for diagnosis, whereas five patients had a diagnostic CT. In these series, as was found in recent literature, the diagnostic potential of the CT was seldom used to its capacity and always in predetermined diagnostic situations.

There is a low degree of utilization of the diagnostic capabilities of the CT in the SPECT/CT context, for a number of reasons. This raises questions about the cost-benefit of investing in high-end CT for SPECT/CT applications.