Speaker
Description
Compton cameras show promise in medical applications in which the performance of gamma cameras is not optimal. This is the case of Targeted Radionuclide Therapy (TRT) assessment, which is gaining interest as a cancer treatment option. In this treatment modality, secondary photon emission from the therapeutic radionuclides can be employed to image the radiopharmaceutical distribution in the body. However, high photon energies and, in the case of alpha therapy, low activities, make conventional gamma cameras sub-optimal for this task. Compton cameras can overcome such problems offering better performance and higher image quality in TRT assessment.
The IRIS group has developed a Compton camera prototype made of monolithic LaBr3 crystals coupled to SiPM arrays that is being evaluated for secondary photon imaging in TRT. The detectors are read out with the ASIC VATA64HDR16 and operated with the AliVATA readout system. The latest prototype version, MACACO III+, is made of two planes. The first one consists of a single detector and the second one is made of four detectors. The prototype has been tested with custom-made Derenzo-like phantoms filled with F-18 and I-131 and also with irregular phantoms with hot spots in a warm background. In addition, mouse phantoms and living mice injected with I-131NaI have been successfully imaged. Simulations of mice undergoing treatments with Ac-225 show very promising results and experimental measurements with this radionuclide are planned.
Good timing resolution is a relevant parameter in Compton imaging, since the operation of the two planes in time coincidence makes it essential to reduce background. In addition, achieving a timing resolution better than 200 ps would allow to identify the backscattering events, further reducing background. Timing information can also be employed for a better determination of the photon interaction.
In spite of the excellent results achieved with the prototype MACACO III+, timing resolution remains to be a parameter to optimize in the prototype. Contrary to PET, Compton cameras have to deal with time walk in signal processing, degrading the timing resolution. In addition, timing resolution in monolithic detectors is challenging due to the spread of the light among the different photodetector pixels, resulting in strong light variations among channels. The group achieved a coincidence time resolution of 1.5 ns in Compton camera mode with the TOFPET2 ASIC from PETsys. However, nonlinearities in the electronics response resulted in a sub-optimal imaging performance.
Current attempts in the system performance improvement are twofold. On one hand, through the use of the FASTIC+ ASIC. On the other hand, the IRIS group coordinates the European project AIDER, which aims at the development of a high performance Compton camera for TRT. The developments include dedicated readout electronics for improved timing resolution.
| Track | FTMI |
|---|---|
| Presentation type | Oral |