Impact of C T-based Attenuation Correction on the Registration Between Dual-gated Cardiac P E T and High-Resolution C T
Abstract: A high-resolution CT (HRCT) used as anatomical prior information during PET reconstruction can enhance the quality of a corresponding low-resolution PET image, provided that it is accurately registered to the PET dataset of interest. In this work, the impact of different PET/CT attenuation correction (AC) protocols on the registration between a dual-gated cardiac 18F-FDG PET image and an HRCT image is investigated. The aim is to explore the impact of AC on PET-toHRCT registration, and to identify the AC strategy that yields the best alignment between the left-ventricles in the PET and the HRCT images for subsequent partial volume correction. Simulations were performed using XCAT phantoms. Shallow breathing and a regular beating pattern were simulated and both noise-free and noisy data were evaluated. Respiratory motion during the acquisition of the CT used for attenuation correction strongly affected the dual-gated PET reconstructions, resulting in artefacts and quantification errors in the PET image and poor PET-to-HRCT registration accuracy. The blurring introduced by the beating heart, on the other hand, proved to have a negligible effect on PET-CT registration. Dual-gated PET images reconstructed without attenuation correction could be well registered to the HRCT if a good initial alignment between the starting images was provided. A commercially available strategy to deal with an AC CT that is acquired in the wrong respiratory phase was also evaluated, and yielded not only enhanced quantitative accuracy but also accurate