The objective of this study is to demonstrate high-resolution positronium lifetime tomography using a 3-dimensional phantom with multiple radioisotopes at activity levels relevant to human imaging. Methods: A cylinder phantom was constructed with a 6-mm thick polycarbonate slab inserted at its center. The phantom was filled with radioactive solutions and scanned in the PennPET Explorer scanner, a long–axial-field-of-view scanner with high sensitivity. Four scans were conducted with 3 different radioisotopes at varying activity levels: 82Rb (240 MBq), 68Ga (110 MBq), and 44Sc (7.4 and 40.7 MBq). The average positron lifetime images were reconstructed with correction for random events. Radial and axial resolutions were measured from lifetime profiles across a hole on the slab and through the slab, respectively. Results: The polycarbonate slab was resolvable in all reconstructed positron lifetime images and showed a lifetime longer than that in water. The lifetime images from 82Rb and 68Ga were noisy because of their low prompt γ yields and high random fractions, whereas noise was substantially reduced in the 44Sc images. The average lifetime estimates were consistent across the 4 scans. The estimated radial and axial resolutions were 3.7 ± 1.8 mm and 3.9 ± 0.4 mm, respectively. Conclusion: This study successfully demonstrated the feasibility of high-resolution positronium lifetime tomography using 82Rb, 68Ga, and 44Sc on the PennPET Explorer.
Huang et al. (Thu,) studied this question.