Improved image resolution on thoracic carcinomas by quantitative 18F-FDG coincidence SPECT/CT in comparison to 18F-FDG PET/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.