Evaluation of a SPECT attenuation correction method using CT data registered with automatic registration software

In recent years, various SPECT attenuation correction systems using CT data have been developed. For attenuation correction of cerebral SPECT data in routine studies, the software method using CT and SPECT data registered with automatic registration software has been used much more than the hardware method using CT data acquired with combined SPECT/CT systems. In this work, the software-based method was compared with a method using TCT data acquired with a sequential SPECT/TCT scan with no subject motion as the golden standard. Attenuation corrected SPECT values using the registered CT data were compared to those using TCT data. Ten sets of normal volunteer data were acquired. The differences in attenuation corrected SPECT values between the SPECT-CT and SPECT-TCT methods were 1.4±1.9% for the entire brain, and the maximum regional difference was 7.8% for both white and gray matter regions. Other regions within the brain where SPECT values were low (e.g., skull, ventricles) were excluded from evaluation. The results indicate that automatic registration software can register CT to SPECT data quite accurately and that a software-based attenuation correction method using CT data can correct attenuation accurately for cerebral data. Consequently, such a software-based attenuation correction method using CT data that requires no specialized hardware seems feasible for use in routine studies.