Factors influencing image quality and lesion detectability of positron emission tomography:a phantom study

摘要

Objective To investigate the influences of acquisition mode,attenuation correction method,and reconstruction algorithm on image quality and lesion detectability of positron emission tomography.Methods The cylinder phantom was prepared with 9 hot columns (4.3-37.8mm in diameter),7 cold columns (5.9-22.3mm) and 7 cold balls (5.8-22.0mm).Four hours after injection of 259MBq 18FDG,serial emission acquisitions were obtained in 2D and 3D modes intermittently for 1,2,4,6,10,15,20,and 30 min.The influences of radioactivity and segmentation process were analyzed on building the attenuation maps.OSEM algorithm was compared with FBP method for reconstruction.Results Compared with 2D mode,the images obtained in 3D mode showed better uni formity in the axial center,and the lesions could be detected with only 1/4-1/2 scan duration.However,the 2D images showed better contrast and clarity.Although segmentation process of attenuation map sacrificed the clarity and accuracy to some extent,it remarkably improved the uniformity,and made the 2-4min transmission scan clinically acceptable.The 22MBq/L radioactivity in the phantom had only 3% decrease to attenuation coefficient of the corresponding region.Images reconstructed with OSEM method showed less stripe noises and better edge clarity,while the FBP-reconstructed images had better contrast.There was no remarkable difference on lesion detectability between the two reconstruction methods.Conclusion Different methods of PET held different advantages and disadvantages,and good knowledge of them will lead to better selection in diversified clinical conditions.