Comparison of PET image quality between germanium transmission attenuation-corrected images and combined PET/CT images.

Abstract

Objectives: Combined PET/CT scanners have been developed. CT data obtained with such a PET/CT is used for attenuation correction of the PET data. Because the CT data are of higher spatial resolution and much lower noise than the transmission data from an external radionuclide source, such as Ge-68, combined PET/CT scanners should have an advantage in attenuated PET image quality. In this study, we compared the quality of actual patients PET images between traditionally attenuation-corrected images using transmission data from external radionuclide source and CT transmission attenuation-corrected images of PET/CT.\nMethods: Seventy-five clinical patients with a known or suspected neoplasm were entered into this study. There were fourteen lung cancers, twelve Head and Neck tumors, seven brain tumors, six cervical cancers of uterus, six rectal cancers, six ovarian tumors, five liver tumors, five bone and soft tissue tumors, three orbital tumors, three renal or adrenal tumors, three breast cancers, two bladder cancers, one esophageal tumor, one cardiac tumor and one pancreas cancer. Eighty-five sets of PET and PET/CT studies were done for seventy-five patients. Fifty C-11 methionine studies and thirty-five FDG studies were performed. Following a traditional PET scan with external radionuclide source, combined PET/CT scan was performed for each set of study. Each of the traditional PET images and combined PET/CT images were visually evaluated. \nResults: Emission images CT-corrected generally showed much lower noise than did germanium-corrected images. Small lesions near bladder such as rectal cancers were generally detected well by CT-corrected FDG PET images, though traditional PET showed much noise derived from FDG in the bladder. Although normal liver showed very high accumulaion of C-11 methionine and there were much noise around the liver, lesions near liver such as renal or adrenal lesions were also generally detected well by C-11 methionine PET/CT. A hepatocellular carcinoma showed fairly good accumulation of FDG by PET/CT, but traditional PET image was not able to detect the lesion because of much noise. \nConclusions: Combined PET/CT scanner showed an advantage in attenuated PET image quality as compared to traditional PET using the transmission data from an external radionuclide source.Society of Nuclear Medicine\u27s 50th Annual Meetin