Organ Specific PET-CT Imaging

摘要

PET-CT scanners with long axial field-of-view are increasingly being used clinically due to their enhanced axial sensitivity. The increased sensitivity can be used to shorten the total scan time thereby improving patient comfort for both step and shoot and CBM scans. For e.g. the axial length of a Biograph Vision Quadra PET-CT scanner (Siemens Medical Solutions USA, Inc.) is 106 cm, Biograph Vision is 26.1 cm, while that of Biograph mMR is about 25.8 cm. For PET-CT reconstruction, the entire PET FOV is scanned by the CT to generate the corresponding mu-maps. In this work, we investigate organ specific PET imaging where just the targeted organs are scanned with CT for attenuation correction. The mu-values of the unsampled regions, that are still within the PET scan range, are jointly estimated using the TOF-PET data. The proposed concept was validated using XCAT simulations as well as clinical PET-CT data acquired on the Biograph Vision scanners. For example, in a whole-body CBM study the PET images were reconstructed using the organ specific CT scan of just the cranial, cardiac and prostrate region and compared to the case when the whole-body CT was used. Another example is a clinical single step and shoot cardiac scan where the transaxial CT slices passing through just the cardiac region was isolated and used in the reconstruction. Using the proposed approach, the bias in the myocardial regions was found to be less than 2% when the truncated organ specific CT was used. The improved TOF timing resolution of 214 picosecond of Biograph Vision was found to localize the effects of attenuation mismatch there-by reducing the bias in the PET reconstructed images.