Application of a performance evaluation standard for a GAGG-scintillator Compton camera

This study aimed at designing performance evaluation standards for clinical Compton imaging systems. We selected
⁵⁷
Co (122 keV),
¹³³
Ba (356 keV), and
²²
Na (511 and 1275 keV) as surrogate radioisotopes whose γ-ray energies are close to those of candidate radioisotopes for future clinical use (such as
^99m
Tc,
¹³¹
I,
¹⁸
F,
⁸⁹
Zr, and
⁴⁴
Sc). We proposed the use of a point source for measuring the sensitivity and the angular resolution measure (ARM) at some points of a field-of-view. A multi-rod phantom (rod diameters: 3, 4, 5, 8 and 10 mm) was designed to evaluate image spatial resolution and a multi-contrast phantom was designed to evaluate image quality (contrast, noise, and uniformity). In this study, based on the proposed evaluation standards, we evaluated a cost-effective Compton camera using GAGG scintillators and a positron emission tomography data acquisition system, which was developed for imaging of astatine-211 in targeted alpha therapy. The full width at half maximus of ARMs were 33°, and 29° for γ-rays of 356 keV and 511 keV, respectively. While no images were obtained for the 122 keV (
⁵⁷
Co) and 1275 keV (
²²
Na) γ rays due to the limited energy range to measure, the multi-rod and multi-contrast phantoms for 511 keV (
²²
Na) could be visualized. The proposed evaluation method enables us to characterize the performance of various Compton imaging systems in the same manner.