Carlotta Trigila et al.
Physics in Medicine & Biology, 67 (2022) 035011
Objective. Molecular radiotherapy is the most used treatment modality against malign and benign
diseases of thyroid. In that context, the large heterogeneity of therapeutic doses in patients and the
range of effects observed show that individualized dosimetry is essential for optimizing treatments
according to the targeted clinical outcome. Approach. We developed a high-resolution mobile gamma
camera specifically designed to improve the quantitative assessment of the distribution and biokinetics
of 131I at patients’s bedside after treatment of thyroid diseases. The first prototype has a field of view of
5 × 5 cm2 and consists of a high-energy parallel-hole collimator made of 3D-printed tungsten,
coupled to a 6 mm thick CeBr3 scintillator readout by an array of silicon photomultiplier detectors.
The intrinsic and overall imaging performance of the camera was evaluated with 133Ba and 131I
sources. In order to test its quantification capability in realistic clinical conditions, two different 3D-
printed thyroid phantoms homogeneously filled with 131I were used. Both single view and conjugate
view approaches have been applied, with and without scatter correction technique. Main Results. The
camera exhibits high imaging performance with an overall energy resolution of 7.68 ± 0.01%, a
submillimetric intrinsic spatial resolution of 0.74 ± 0.28 mm and a very low spatial distortion
0.15 ± 0.10 mm. The complete calibration of the camera shows an overall spatial resolution of
3.14 ± 0.03 mm at a distance of 5 cm and a corresponding sensitivity of 1.23 ± 0.01 cps/MBq, which
decreases with distance and slightly changes with source size due to the influence of scattering. Activity
recovery factors better than 97% were found with the thyroid phantoms. Significance. These
preliminary results are very encouraging for the use of our camera as a tool for accurate quantification
of absorbed doses and currently motivates the development of a fully operational clinical camera with
a 10 × 10 cm2 field of view and improved imaging capabilities.