Periodic Reporting for period 3 - GAMMA-MRI (gamma-MRI: the future of molecular imaging)
Periodo di rendicontazione: 2023-10-01 al 2024-09-30
GAMMA-MRI has introduced not merely a hybrid approach combining existing technologies, but an entirely new imaging modality. It simultaneously achieves the high spatial resolution of MRI and the high sensitivity of gamma photons detection as in nuclear medicine techniques. Unlike conventional MRI or PET-MRI systems, GAMMA-MRI does not require ultra-high magnetic fields, expensive electromagnetic shielding, or coincidence detection of gamma rays, thereby resulting in a less complex and more affordable solution compared to current state-of-the-art systems, especially hybrid ones.
The key objectives that have been successfully achieved in the GAMMA-MRI project are:
G1: Efficient hyperpolarisation of several radioactive isotopes of xenon (mXe).
G2: Preservation of mXe hyperpolarisation long enough to reach the targeted object of interest from the administration site.
G3: Development of compressed sensing strategies to obtain GAMMA-MRI images.
G4: Integration of unique, compact, fast, magnetic-field-compatible, high-performance gamma detectors and electronics.
G5: Construction of a prototype device for in vitro and in vivo demonstration of the GAMMA-MRI technique.
The pioneering GAMMA-MRI project has demonstrated the feasibility of a new imaging technique, laying the foundation for future developments in accessible and high-performance diagnostic imaging using radioactive rare gases, such as xenon.
One major achievement was the optimisation and standardisation of the production of two key xenon isomers, 129mXe and 131mXe, in two European nuclear reactors, a significant step forward in developing novel MR-based radiotracers.
Two Spin Exchange Optical Pumping (SEOP) systems were also developed, extensively tested, and validated through Nuclear Magnetic Resonance (NMR) and gamma-detection experiments, achieving over 40% polarisation for stable 129Xe and about 30% for radioactive 129mXe, a significant breakthrough supporting the GAMMA-MRI methodology.
A flexible NMR system was built, incorporating custom RF coils and digital electronics for precise monitoring of xenon polarisation, and facilitating indirect measurements through gamma-asymmetry detection after RF pulses. Simulation tools based on Bloch equations and Monte Carlo methods were developed to optimise the experiments and predict signal behaviour under varying conditions.
The project culminated in the construction of a low-field GAMMA-MRI prototype, built around a homogeneous permanent magnet integrating fast gamma detectors. Complete integration of RF coils, gradient systems, and shimming elements was achieved and successfully validated through ¹H and ¹²⁹Xe MRI experiments and gamma-asymmetry measurements, marking the first realisation of the GAMMA-MRI technique.
The GAMMA-MRI project outcomes are already influencing ongoing research activities. Key technical developments, including the SEOP systems and the integrated gamma-NMR modules, are being considered for further development and commercialisation. The project has led to several scientific publications, with others submitted for peer review and more in preparation, along with presentations at international conferences.
Our work has provided European leaders in science and technology with a unique competitive advantage in developing next-generation imaging modalities, applicable in preclinical and clinical settings for multi-tracer, real-time, high-speed, and high-sensitivity studies.
During the course of the project, several critical science-to-technology breakthroughs were accomplished:
- Efficient hyperpolarisation of metastable xenon isotopes (mXe) through Spin Exchange Optical Pumping (SEOP).
- Successful storage and transport of Hyperpolarized gamma-emitting tracers, enabling the separation of hyperpolarisation and imaging phases.
- Development of fast, compact, high-sensitivity gamma detectors compatible with magnetic fields and capable of high count rates.
- Development of advanced data acquisition strategies, including compressed sensing methods.
The project also delivered a low-field prototype GAMMA-MRI device, which successfully combined all these technological advances. Tests using 1H and 129Xe MRI, along with gamma-asymmetry detection experiments, demonstrated the technique's potential for revolutionary in vitro and possibly in vivo imaging applications.
GAMMA-MRI offers major advantages for healthcare: reduced device cost (estimated under €100,000), portability, enhanced safety through lower magnetic fields, and improved accessibility to molecular imaging at the point-of-care. Initially focused on brain perfusion and stroke diagnosis, the technology is adaptable to other organs and clinical applications. The project’s results are expected to create new jobs in the imaging and medical technology sectors, and to contribute significantly to budget savings in European healthcare systems by shifting towards simpler, more affordable imaging devices.