Multi-Emission Radioisotope - Marine Animal Imaging Device+ (MERMAID+)

• Applicant: Professorin Magdalena Rafecas, Ph.D.
• Subject Area: Medical Physics, Biomedical Technology ; Animal Physiology and Biochemistry
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 496099829

MERMAID+ aims to make in-vivo radioisotope imaging of small aquatic animals practicable. To this end, we will develop and characterize a proof-of-concept (PoC) device for positron emission tomography (PET) dedicated to small fish and mussels, and explore its combination with other imaging modalities. In the long-term, the MERMAID+ concept will be applied to research on sustainable fish farming (integrated multi trophic aquaculture) and biomedical research, as certain fish species (e.g. zebrafish) are being increasingly used as models for various human diseases (Alzheimer, diabetes, arteriosclerosis...). Thanks to the development of dedicated PET scanners for rodents, significant advances in pre-clinical and translational research have been achieved using specific radiotracers. Unfortunately, in-vivo functional imaging of fish is still very limited. While for transparent larvae optical methods might be sufficient, for adult zebrafish and other fish species further modalities are desired; on the other hand, molecular nuclear imaging for fish remains challenging. MERMAID+ aims to address these challenges. Preliminary work has been carried out within the project "Multi-Emission Radioisotopes - Marine Animal Imaging Device" (MERMAID), supported by one-year EU-ATTRACT seed funds. Within MERMAID+, our two-module PET prototype will be upgraded to 16 modules, and a CT device will be incorporated. Calibration and characterisation will be carried out with dedicated phantoms. Using i.a. 3D-printing technology, a fish phantom will be developed, as well as a dedicated imaging chamber. The latter includes fresh-water and anaesthesia supply and gentle fish immobilization. Regarding the possible use of non-pure PET tracers with emission of gamma rays, we will investigate the combination of PET with a Compton camera (CC) by means of Monte-Carlo simulations. The CC aims to increase the detection sensitivity by detecting single gamma rays; t should also complementary tomographic information. To exploit this unique hybrid detection concept, we will develop a novel image reconstruction algorithm capable to jointly reconstruct PET and CC data into a single image. This new approach requires i.a. dedicated and matched models of radioactive decay and detection processes for the two modalities. Image-quality phantoms will be simulated to study the effects on the image of various radioisotopes, configurations and reconstruction approaches. MERMAID+ this contains extremely original research: PoC system with water-filled imaging chamber, reconstruction algorithms, and novel application. The outcomes of MERMAID+ are relevant for those research fields that focus on the physiology and pathology of fish. Additionally, our methods are also of interest for other areas, as the envisioned software can be transferred to other applications and imaging configurations, and the fish imaging chamber can be adapted to other imaging modalities or commercial scanners.

• DFG Programme: Research Grants