Impact of Patient Size on Image Quality in Clinical PET with a Convergent Penalized-Likelihood Image Reconstruction Algorithm

Abstract

A penalized-likelihood (PL) image reconstruction algorithm using the relative difference penalty (RDP), called a PL-RDP algorithm, has recently been developed for clinical PET and has previously demonstrated improved Iesion quantitation accuracy and Iesion detectability over the current clinical standard PET image reconstruction algorithm, ordered subsets expectation maximization (OSEM). Patient size is one of the main factors affecting PET image quality, but the effects of patient size on PL-RDP have not been investigated. The purpose of this study was to evaluate the impact of patient size on image quality for PL-RDP compared to OSEM. We inserted simulated liver Sesions with varying sizes and contrasts into clinical data. To evaluate Iesion detectability, we applied a channelized Hotelling observer and calculated the signal-to-noise ratio (SNR). To evaluate Iesion quantitation accuracy, we compared contrast recovery coefficient (CRC) at matched image roughness, which is a surrogate image noise measure. The Iesion detectability and the quantitation accuracy in a group of smaller-sized patients with body mass index (BMI) 26 kg/m2. The detection performance of TOF PL-RDP was better than that of TOF OSEM for 20 mm Iesions with contrast $\geq 0.5$ in the smaller-sized patient group; and for 10 mm Iesion with contrast $\geq$ 1.25, 15 mm Iesions with contrast $\geq 0.5$ and 20 mm Iesions with contrast $\geq$ 0.25 in the larger-sized patient group. The detectability for non-TOF PL-RDP was better than that for non- TOF OSEM for 20 mm Iesions with contrast $\geq 0.5$ in the Iarger- sized patient group. The quantitation performance of non-TOF PL-RDP was better than that of non-TOF OSEM for 20 mm Iesions with contrast $\geq 0.5$, 15 mm Iesions with contrast $\geq 1$, and 10 mm Iesions with contrast $\geq 4$ in the smaller-sized patient group; and for 20 mm Iesions with contrast $\geq 0.5$, 15 mm Iesions with contrast $\geq 0.5$, and 10 mm Iesions with contrast $\geq 4$ in the larger-sized patient group. In addition, the improvement of PL- RDP in detection over OSEM for the larger-sized patients was larger than that for the smaller-sized patients for 15 mm Iesion with contrast $\geq 0.75$ and 20 mm Iesions with contrast $\geq 0.5$ in the TOF case; and the improvement of PL-RDP in quantitation accuracy over OSEM for the larger-sized patients was larger than that for the smaller-sized patients for 20 mm Sesions with contrast $\geq 0.5$ in the non-TOF case.