A new multimodality system for quantitative in vivo studies in small animals: combination of nuclear magnetic resonance and the radiosensitive β-microprobe

Elucidating complex physiological mechanisms in small animal in vivo requires the development of new investigatory techniques including imaging with multiple modalities. Combining exploratory techniques has the tremendous advantage to record simultaneously complementary parameters on the same animal. In this field, an exciting challenge remains in the combination of nuclear magnetic resonance (NMR) and positron emission tomography (PET) since small animals studies are limited by strict technical constraints in vivo. Coupling NMR with a radiosensitive β-microprobe offers therefore an interesting technical alternative. To assess the feasibility of this new dual-modality system, we designed theoretical and experimental approaches to test the ability of the β-Microprobe to quantify radioactivity concentration in an intense magnetic field. In an initial step, simulations were carried out using Geant4. First, we evaluated the influence of a magnetic field on the probe field of view. Then, the detection sensitivity and energy response of the probe were quantified. In a second step, experiments were run within a 7-T magnet to confirm our simulations results. We showed that using the probe in magnetic fields leads to a slight attenuation in sensitivity and an increase of the scintillation light yield. These data showed the feasibility of combining NMR to the β-microprobe.