Motion artifacts and correction techniques in PET/CT

PET/CT is a very important imaging tool in the management of the oncology patients. PET/CT hardware registration between the sequential imaging of CT and PET with the same imaging table has significantly improved the registration between the anatomy in CT and the functional information in PET. However, registration between the CT and PET images remains an issue in the thorax and the abdomen, where the anatomy moves with the respiratory motion and the snapshot CT images may not register well with the average PET images. Respiratory gating has been proposed for CT and PET, but its adaption in the clinic can only be found with the respiratory-gated CT or 4D-CT in radiation therapy treatment planning. Majority of the PET/CT practices are not using any CT or PET gating due to the complexity of gating and the challenge of finding the right patient for gating before PET/CT imaging. In this chapter, we will not only cover the more complex gated CT and gated PET techniques but also introduce the simple average CT technique of less than 1 mSv to improve the registration of CT and PET and to provide the important CT data for dose calculation and image guidance in radiation therapy.