Speaker
Description
Conventional Micromegas detectors are typically based on charge readout, which requires a complex electronic chain and becomes increasingly demanding for large-area and high-granularity requirements. As an alternative, optical readout Micromegas detectors use cameras and optical elements to record the scintillation light produced during avalanche multiplication.
Such detectors have demonstrated promising performance for the imaging of X-rays, neutrons, and beta particles. In neutron imaging, the aim is real-time operation in high-radiation environments for applications related to radioactive waste and nuclear fuel characterization. In beta imaging, these detectors are being developed to investigate low-activity radiolabelled samples, with the long-term objective of imaging isotope distributions at the cellular scale. Specifically, this approach could support the development of more effective anti-cancer therapies by enabling the characterization, in pre-clinical models, of the intracellular accumulation of dual labelled antibody–drug conjugates (ADCs). These ADCs would incorporate a tritiated (3H) drug and a 14C-labelled protein component, allowing their distribution to be tracked within individual tumour cells.
In this context, optimizing the optical imaging system to achieve high spatial resolution and sensitivity is a central aspect of this work, with performance determined by both the detector design and the optical chain, including the lens and the camera. An X-ray generator was used to compare detectors with different characteristics, including a non-reflective black mesh, a standard mesh, and a detector incorporating a wavelength shifter (WLS). Spatial resolution was evaluated using a dedicated target with line patterns of varying spatial frequencies. The black-mesh detector operated with an Ar/CF4 gas mixture delivered the best performance, due to reduced light reflections, whereas the WLS-based detector showed degraded resolution as a result of diffusion in the Ar/isobutane gas mixture. In addition, optimization of the optical chain through the use of different lenses made it possible to image X-ray beams with dimensions down to a few tens of micrometres.
For beta imaging, 3H-labelled glucose samples with activities ranging from 10 Bq to 0.01 Bq were studied, and dedicated analysis made it possible to detect drops with activities down to 0.1 Bq. A triple gas mixture of Ar/CF4/Isobutane showed very promising performance, improving detector stability while maintaining sufficient light yield even without the use of a wavelength shifter. In addition, 14C-labelled and 3H-labelled glucose with the same activity were measured simultaneously, demonstrating the feasibility of discriminating between the two isotopes. Imaging of cells constitutes the next step of this work and is currently underway.
| Name of the speaker | Elisavet Fasoula |
|---|---|
| Eligible for the Georges Charpak Young Scientist Award. | yes |