Miniaturized Compton gamma camera: More tests
The MiniPIX TPX3 based ultra/compact gamma camera introduced in the previous article by Dr. Jan Jakubek was tested with several different gamma emitting isotopes. Here we show the result of one experiment with three sources:
- Iodine I-131 (gamma line at 364 keV),
- Sodium Na-22 (annihilation gamma line at 511 keV)
- Cesium Cs-137 (gamma line at 662 keV)
All of them were placed in front of the MiniPIX TPX3 detector with a 2 mm thick CdTe sensor. The gamma radiation was recorded and the images were reconstructed for different energy channels. The result is graphically summarized in the following animation.
The result shows that the image reconstruction is nicely energy selective: The position of each source reconstructed in the selected energy interval is shown clearly without any traces of the other two sources.
It is important to remind that the detector does not use collimators for image formation. It uses a reconstruction of the Compton scattering effect occurring in its monolithic sensor. That is why it does not require any heavy shielding. Its total weight is just 41 g.
The angular resolution depends on the energy of gamma rays and statistics. Now with our current reconstruction algorithm, it is 4-9 degrees. Our models predict possible improvement by a factor of 2.
The sensitivity of the camera corresponds to the probability of Compton scattering in the single CdTe sensor (14x14x2 mm3) followed by absorption of a scattered gamma photon. The sensitivity can be easily increased using several MiniPIX TPX3 units.