Hybrid PET/MRI of large vessel vasculitis : Radiation dose compared to PET/CT with view on cumulative effective dose.

Abstract

The diagnosis of large vessel vasculitis (LVV) is often challenging due to the various clinical appearances and the low prevalence. Hybrid imaging by positron emission tomography and computed tomography (PET/CT) is ahighly relevant imaging modality for diagnostics and disease surveillance but may be associated with asignificant amount of radiation dose especially in patients with complications. The aim of this retrospective analysis was to compare the image quality and impact of hybrid imaging methods PET/CT and PET/MRI on the potential for dose reduction. This retrospective single-center study included acohort of 32patients who were referred to PET/MRI for the evaluation of LVV, including graft infections and fever of unknown origin. This cohort was compared to asimilar cohort of 37patients who were examined with PET/CT in the same period. Mean radiation dose as well as image quality to establish adiagnosis were compared between the groups. The mean radiation dose applied in PET/MRI was significantly lower when compared to PET/CT (mean 6.6 mSV vs. 31.7 mSV; p < 0.001). This effect was based on the partially multiphasic CT protocols. At the same time, diagnostic image quality using a4-point scale showed similar results for both imaging modalities in the work-up of LVV. With PET/MRI, the radiation exposure can be significantly reduced with similar image quality and diagnostic impact. Patients with LVV have ahigher risk of receiving aclinically relevant cumulative effective dose (CED) and PET/MRI should be made available to them.