Attenuation Correction Methods Suitable for Brain Imaging with a PET/MRI Scanner: A Comparison of Tissue Atlas and Template Attenuation Map Approaches

Modeled attenuation correction (AC) will be necessary for combined PET/MRI scanners not equipped with transmission scanning hardware. We compared 2 modeled AC approaches that use nonrigid registration with rotating 68Ge rod–based measured AC for 10 subjects scanned with 18F-FDG.Methods: Two MRI and attenuation map pairs were evaluated: tissue atlas–based and measured templates. The tissue atlas ap-proach used a composite of the BrainWeb and Zubal digital phantoms, whereas the measured templates were produced by averaging spatially normalized measured MR image and cor-egistered attenuation maps. The composite digital phantom was manually edited to include 2 additional tissue classes (para-nasal sinuses, and ethmoidal air cells or nasal cavity). In addition, 3 attenuation values for bone were compared. The MRI and attenuation map pairs were used to generate subject-specifi