Abstract
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Objectives To determine the optimal reconstruction algorithm in FDG PET tests with short acquisition time (SAT).
Methods In phantom studies, an NEMA phantom with 6 spheres filled with FDG (sphere size: 6.23-37 mm; radioactivity ratio of spheres to background = 8:1) was evaluated. Image acquisition time was varied between 15 and 180 s, and obtained image data were reconstructed using both FORE+OSEM and 3D-OSEM algorithms. Further, in clinical studies, 19 cases of mid-abdominal images were evaluated by putting 3 kinds of ROIs having different counts. All obtained images were investigated visually as well as quantitatively, using SUV and coefficient of variation (CV).
Results In phantom studies, FORE+OSEM images with SAT showed large CVs (poor image quality) whereas SUVs were comparatively constant. 3D-OSEM images showed comparatively constant CVs (good image quality) whereas SUVs had significantly decreased. The results of visual evaluation were well correlated with those of quantitative evaluation. Small spheres were obscured on 3D-OSEM images with SAT although their image quality was not greatly deteriorated. Clinical studies yielded results similar to phantom examinations.
Conclusions FDG PET images with SAT reconstructed by FORE+OSEM showed poor image quality whereas images reconstructed by 3D-OSEM showed obscured uptake. FORE+OSEM reconstruction might be useful under SAT because FORE+OSEM images showed clear FDG uptakes, which can be identified by comparing them with simultaneously obtained CT images
Results of phantom study
*: statistically significant
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