Speaker
Description
Hybrid systems integrating Positron Emission Tomography (PET), Magnetic Resonance Imaging (MRI), and Focused Ultrasound (FUS) are highly attractive for preclinical imaging and therapy monitoring, yet no commercial trimodal solution is currently available. In this work, we present the development and validation of a dedicated preclinical PET insert designed for simultaneous operation with high-field MRI and commercial FUS devices, and we demonstrate its potential in both trimodal imaging applications and positron-range confinement studies at 9.4 T. The system is based on monolithic LYSO crystals and provides an axial field of view of 67 mm. Performance evaluation, inspired by the NEMA NU-4 2008 protocol, showed a homogeneous submillimeter spatial resolution of 0.9 mm with depth-of-interaction capability, a sensitivity of 3.8%, and a peak Noise Equivalent Count Rate of 80 kcps. Image quality measurements yielded recovery coefficients up to 0.89 and spill-over ratios of 11% in air and 22% in water, demonstrating performance comparable to state-of-the-art preclinical PET systems.
Beyond technical validation, the PET insert was employed in different trimodal experiments. In a first phantom proof-of-concept, the system was combined with a custom low-field MRI and a dedicated FUS device. Focused ultrasound was used to locally heat the phantom and melt a gelatin barrier, enabling the redistribution of an initially confined ¹⁸F-FDG solution. This process was successfully monitored over time by PET-MRI, showing the ability of the platform to track FUS-induced changes in tracer distribution. In addition, in vivo feasibility was demonstrated in murine brain studies using the PET insert together with a 9.4 T MRI scanner and a commercial FUS system. Blood–brain barrier opening was induced with microbubbles, and co-administered Gd-DOTA and ⁶⁴Cu-DOTA allowed MRI and PET to confirm co-localized enhancement in the sonicated regions.
Finally, the system was used to experimentally investigate positron-range confinement under strong magnetic fields. Thin glass capillaries filled with ¹⁸F, ⁸⁹Zr, and ⁶⁸Ga were imaged inside and outside a 9.4 T MRI scanner in different phantom materials and orientations relative to the magnetic field. While ¹⁸F showed minimal changes, higher-energy emitters exhibited a clear anisotropic reduction of positron-range blurring inside the MRI. For ⁸⁹Zr, improvements of about 25% were observed, whereas for ⁶⁸Ga the reconstructed FWHM decreased by up to 32–39%, with FWTM reductions reaching 56–58% depending on phantom density. These findings were further supported by microDerenzo measurements, where the magnetic field enabled improved rod separation for high-energy emitters, including resolution of 1.0 mm rods for ⁶⁸Ga at 9.4 T. Overall, this work demonstrates the versatility of the proposed trimodal PET-MRI-FUS platform for system validation, image-guided therapy monitoring, and high-field preclinical PET studies.
| Track | PSMR |
|---|---|
| Presentation type | Oral |