Investigation of using anatomical knowledge in PET imaging of sub-centimeter lung nodules

Positron emission tomography (PET) is a valuable clinical tool for cancer staging and monitoring response to treatment, but it is limited by its relatively poor resolution and high noise level. In this study, we investigated the impact of using anatomical information, either during or post reconstruction, for PET imaging of sub-cm lung nodules. The XCAT phantom with four inserted lung lesions (diameter: 6–12 mm, contrast: 4:1) was used to simulate twenty 3-minute [ 18 F]-FDG PET thorax scans on a Siemens mCT. Maximum a posteriori reconstruction with an anatomical prior was compared to ordered-subsets expectation-maximization with resolution recovery (with and without the use of time-of-flight (TOF) information). Furthermore, an anatomy-guided partial volume correction (PVC) technique was applied to each of these reconstructions. Adding TOF information improved both the convergence and the contrast-to-noise ratio (CNR). The anatomical prior further improved the CNR at the cost of a systematic bias. The template-based PVC method improved the quantitative accuracy for all reconstructions, within a clinically acceptable number of iterations. By combining the anatomical prior with the anatomy-guided PVC technique, quantitatively accurate, high-contrast PET imaging could be achieved even for the smallest lung nodule (6 mm), provided that the nodule was visible on CT and accurate respiratory motion correction has been performed.