Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 49 (2016)

Hyperpolarizationofof flowing
flowing water
water by dynamic
dynamic nuclear
Hyperpolarization
nuclearpolarization
polarization
K. Yamada, *1, *2 K. Tateishi,*1 and T. Uesaka*1

߳ ൌ ͳ െ ߩ݂‫ݏ‬หߛ݁ หఊ೙,where ߩ is the coupling factor, ݂ is the leakage factor, ‫ݏ‬is the saturation factor, and ߛ௘ and ߛ௡ are thegyromagnetic ratios of the electron and 1H, respectively.
With the above setup, ߩ, ݂, and ‫ ݏ‬are estimated to be 0.07,0.90, and 1, respectively,3) and the expected polarization is0.0041 %.
*1*2RIKEN Nishina Center
Department of Physics, Toho University- 172 -NMR
Gel functionalized with radicalMicrowave
MRI system
NMR CoilCylindricalli dcavity
i TE011 (9 GHGHz)
Pump (1.5 mL/min)) Electromagnet (0.3 T)

Fig. 1. Experimental set up for flow-DNP.
We constructed the system except for the gel this time, anddetected the NMR signal of 1H spins in the flowing waterwith a flow rate of ͳǤͷȀ for demonstration. The
result is shown in Fig. 2. Although the line width is a littlebroad compared to the one obtained from a conventional
solution NMR, it is narrow enough for flow-DNP. Next year,
we will synthesize the gel and carry out the flow-DNP
experiment.
signal intensity (a.u.)

Magnetic resonance angiography (MRA) is a techniquefor imaging blood vessels based on magnetic resonanceimaging (MRI) for the evaluation of aneurysms, stenosis,
occlusions, and so on. To obtain clear images, imaging timeneed to be done for a long for signal averaging, and thismakes the resolution, in particular of heart, worse due to thebeating. To overcome this problem, the injection of polarizedwater into a blood vessel was demonstrated1). Both theimaging time and the resolution were improved through theuse of this method. In this experiment, the polarized 1H spinsin water were generated by dynamic nuclear polarization(DNP) method. The method can be used to polarize > 30%of 1H spins using cryogenics and sub-terahertz devices,
however, about 90% of the polarization was relaxed before
injection, due to the short spin-lattice relaxation time of 1H
spins.2) In this work, we adopted the flow-DNP method topolarize 1H spins in flowing water for simplicity.
The DNP method is used to transfer electron spinpolarization to nuclei with microwave irradiation. We
applied it to flowing water (flow-DNP).3) This is a very
compact, cheap, and versatile method for polarizing liquidstate samples. We would like to apply this method not onlyto MRA but also for various studies such as on proteins using
high-resolution NMR system.4)
Experimental setup of flow-DNP is shown in Fig. 1. Amicrowave cavity with a frequency of ͻ  is placed in
the electromagnet. The external magnetic field is set at ͲǤ͵.
Water is flowed into the cavity by a pump. The tube in thecavity is filled with gels functionalized with radicals to slow
down the flow rate only inside the cavity. The microwave
irradiates the radicals with an incident power of ͵ .
Although the polarized water is looped back to the pump incurrent setup, it will be sent to the MRI system in the future.
The coil in the NMR is placed in the downstream directionof the cavity to check the polarization. The enhancement
factor ߳ of the polarization is given as

10.50-150-100-50050
offset (kHz)

100150Fig. 2. NMR signals of the 1H spins in flowing water inthermal equilibrium. Offset means the difference between theresonance frequency of 1H and the frequency ofelectromagnetic waves.
References

1) J. Ardenkjaer-Larsen et al., Magn. Reson. Med. 71, 50 (2014).
2) Q. Chappuis et al., J. Phys. Chem. Lett. 6, 1674 (2015).
3) M. D. Lingwood et al., J. Magn. Reson. 205, 247 (2010).
4) M. Reese et al., J. Am. Chem. Soc. 131, 15086 (2009).