Effect of scatter correction when comparing attenuation maps: Application to brain PET/MR

摘要

In PET imaging, attenuation and scatter corrections are an essential requirement to accurately quantify the radionuclide uptake. In the context of PET/MR scanners, obtaining the attenuation information can be challenging. Various authors have quantified the effect of an imprecise attenuation map on the reconstructed PET image but its influence on scatter correction has usually been ignored. In this paper, we investigate the effects of imperfect attenuation maps (μmaps) on the scatter correction in a simulation setting. We focused our study on three μmaps: the reference μmap derived from a CT image, and two MR-based methods. Two scatter estimation strategies were implemented: a μmap-specific scatter estimation and an ideal scatter estimation relying only on the reference CT μmap. The scatter estimation used the Single Scatter Simulation algorithm with tail-fitting. The results show that, for FDG brain PET, regardless of the μmap used in the reconstruction, the difference on PET images between μmap-specific and ideal scatter estimations is small (less than 1%). More importantly, the relative error between attenuation correction methods does not change depending on the scatter estimation method included in the simulation and reconstruction process. This means that the effect of errors in the μmap on the PET image is dominated by the attenuation correction, while the scatter estimate is relatively unaffected. Therefore, while scatter correction improves reconstruction accuracy, it is unnecessary to include scatter in the simulation when comparing different attenuation correction methods for brain PET/MR.