Radiation doses from low-dose CT scans in SPECT/CT and PET/CT examinations: A survey in Germany.

Aim: Recently, dose reference levels (DRLs) have been defined in Germany for auxiliary low-dose CT scans in hybrid SPECT/CT and PET/CT examinations, based on data from 2016/17. Here, another survey from 2020 was evaluated and compared with the new DRLs as well as with similar surveys from foreign countries.
Methods: The survey, which had already been conducted in the Nordic countries, queried for various examinations including the following values: patient weight and height, volume CT dose index (CTDI _vol ), dose length product (DLP). For each examination, statistical parameters such as the third quartile (Q3) were determined from all submitted CTDI _vol and DLP values. Additionally, for examinations comprising datasets from at least 10 systems, the third quartile (Q3-Med) of the respective median values of each system was calculated. Q3 and Q3-Med were compared with the newly published DRLs from Germany and values from similar studies from other countries.
Results: Data from 15 SPECT/CT and 13 PET/CT systems from 15 nuclear medicine departments were collected. For the following examinations datasets from more than 10 systems were submitted: SPECT lung VQ, SPECT bone, SPECT&PET cardiac, PET brain, PET oncology. Especially for examinations of the thorax and heart, the new DRLs are very strict compared to this study. The CTDI _vol values for examinations of the head were lower in this study than the DRLs prescribe now.
Conclusions: For certain examination types, there is a need for dose optimization at some clinics and devices in order to take into account the new DRLs in Germany in the future.
Competing Interests: The authors declare that they have no conflict of interest.
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