National survey of patient doses from hybrid methods in nuclear medicine – SPECT-CT and PET-CT
- Avramova-Cholakova, M. Garcheva, M. Dimcheva, E. Petrova,S. Ivanova4, M. Dimitrova, Y. Palashev
Recent years two types of hybrid systems were installed in Bulgaria – Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), combined with an X-ray computed tomography (CT) system. The aim of this work is to perform national survey of patient doses from SPECT-CT and PET-CT procedures, to explore potential for optimization and to elaborate national diagnostic reference levels. The survey included all hybrid systems in the country – four SPECT-CT and two PET-CT. Effective doses were estimated for total of 540 patients. Ten types of SPECT-CT and two types of PET-CT examinations were considered. Effective doses from the nuclear medicine component were calculated applying the ICRP 53 and ICRP 80 conversion coefficients. Computed tomography dose index (CTDI) and dose length product (DLP) were retrospectively obtained from the archives of the systems. Effective doses from the CT component were calculated with CT-Expo software. Parallel estimation of CT component contribution with the NRPB conversion coefficients was done where applicable. Big differences in SPECT-CT practice were found with potential for optimization. The CT protocols and activities applied differ even for the systems of the same model. Effective doses from PET-CT have close values for both systems. Comparison with literature data reveals that PET-CT doses are relatively low. National diagnostic reference levels are elaborated for SPECT-CT and PET-CT procedures.
Key words: SPECT-CT. PET-CT. PATIENT DOSES. DRL