LED-Based Photo-CIDNP Hyperpolarization Enables 19 F MR Imaging and 19 F NMR Spectroscopy of 3-Fluoro-DL-tyrosine at 0.6 T

Although 19 F has high potential to serve as a background-free molecular marker in bioimaging, the molar amount of marker substance is often too small to enable 19 F MR imaging or 19 F NMR spectroscopy with a sufficiently high signal-to-noise ratio (SNR). Hyperpolarization methods such as parahydrogen-based hyperpolarization or dynamic nuclear polarization (DNP) can significantly improve the SNR, but require expensive and complex sample preparation and the removal of toxic catalysts and solvents. Therefore, we used the biologically compatible model of the fluorinated amino acid 3-Fluoro-DL-tyrosine with riboflavin 5ʹ-monophosphate (FMN) as a chromophore dissolved in D 2 O with 3.4% H 2 O dest. , allowing to transform light energy into hyperpolarization of the 19 F nucleus via photo-chemically induced dynamic nuclear polarization (photo-CIDNP). We used a low-cost high-power blue LED to illuminate the sample replacing traditionally used laser excitation, which is both potentially harmful and costly. For the first time, we present results of hyperpolarized 19 F MRI and 19 F NMR performed with a low-cost 0.6 T benchtop MRI system. The device allowed simultaneous dual-channel 1 H/ 19 F NMR. 19 F imaging was performed with a (0.94 mm) 2 in-plane resolution. This enabled the spatial resolution of different degrees of hyperpolarization within the sample. We estimated the photo-CIDNP-based 19 F signal enhancement at 0.6 T to be approximately 465. FMN did not bleach out even after multiple excitations, so that the signal-to-noise ratio could be further improved by averaging hyperpolarized signals. The results show that the easy-to-use experimental setup has a high potential to serve as an efficient preclinical tool for hyperpolarization studies in bioimaging.