Dose optimization: a review of CT imaging for PET attenuation correction

Review limitations and benefits of various options for CT-based attenuation correction for PET/CT studies. With the combination of PET and CT, came the combination of patient radiation dose from the two imaging modalities. Modern advances in CT technology provide opportunities to design CT acquisitions for attenuation correction allowing for the optimization of the attenuation correction acquisition for specific clinical purposes. We reviewed published literature, accepted practices, and the authors' experience, to identify and classify various tailored approaches for CT attenuation correction of PET emission data. ImageWisely recommends three broad categories for dose optimization of attenuation correction in PET/CT imaging: (1) attenuation correction at diagnostic CT quality (PET/CTD); (2) attenuation correction for anatomic localization only of PET images (PET/CTAL); and (3) for PET attenuation correction only (PET/CTAC). The advantages, disadvantages, and dosimetry for each approach are considered. Modern dose reduction techniques allow some CTAL and CTAC exams to have a sufficient image quality for anatomic localization at radiation dose levels equivalent to the previous radionuclide attenuation correction method with [68-Ge/68-Ga] transmission sources. Thus, the major justifications for combining diagnostic quality CTD with PET would be to provide excellent anatomic image correlation in the cases, where subtle functional or lesion uptake requires greater localization refinement, and to reduce patient dose by removing the CTAC or CTAL exam in conjunction with a separate diagnostic CT in lieu of a single CTD exam. The choice of method depends on a variety of factors, including institutional and physician preference and experience, and technology availability.