Improvedimageresolutiononthoraciccarcinomasbyquantitative18F-FDGcoincidenceSPECT/CTincomparisonto18F-FDGPET/CT

Currently,18F-FDG coincidence SPECT（Co-SPECT）/CT scan still serves as an important tool for diagnosis,staging,and evaluation of cancer treatment in developing countries.We implemented full physical corrections（FPC） to Co-SPECT（quantitative Co-SPECT） to improve the image resolution and contrast along with the capability for image quantitation.FPC included attenuation,scatter,resolution recovery,and noise reduction.A standard NEMA phantom filled with 10:1 F-18 activity concentration ratio in spheres and background was utilized to evaluate image performance.Subsequently,15 patients with histologically confirmed thoracic carcinomas were included to undergo a 18 F-FDG Co-SPECT/CT scan followed by a 18 F-FDG PET/CT scan.Functional parameters as SUVmax,SUVmean,SULpeak,and MTV from both quantitative Co-SPECT and PET were analyzed.Image resolution of Co-SPECT for NEMA phantom was improved to reveal the smallest sphere from a diameter of 28 mm to 22 mm（17 mm for PET）.The image contrast was enhanced from 1.7 to 6.32（6.69 for PET） with slightly degraded uniformity in background（3.1% vs.6.7%）(5.6% for PET).Patients' SUVmax,SUVmean,SULpeak,and MTV measured from quantitative Co-SPECT were overall highly correlated with those from PET（r=0.82-0.88）.Adjustment of the threshold of SUVmax and SUV to determine SUVmean and MTV did not further change the correlations with PET（r=0.81-0.88）.Adding full physical corrections to Co-SPECT images can significantly improve image resolution and contrast to reveal smaller tumor lesions along with the capability to quantify functional parameters like PET/CT.