Optical Pumping System Design for Large Production of HyperpolarizedXe129

Abstract

We present a design for a spin-exchange optical pumping system to produce large quantities of highly polarized 129Xe. Low xenon concentrations in the flowing gas mixture allow the laser to maintain high Rb polarization. The large spin-exchange rate between Rb and 129Xe through the long-lived van der Waals molecules at low pressure, combined with a high flow rate, results in large production rates of hyperpolarized xenon. We report a maximum polarization of 64% achieved for a 0.3 l/h Xe flow rate, and maximum magnetization output of 6 l/h at 22% polarization. Our findings regarding the polarization dependence on temperature, nitrogen partial pressure, and gas mixture flow velocity are also reported.

Large Production System for Hyperpolarized 129Xe for Human Lung Imaging Studies

“…The maximum 129 Xe polarization achieved with our system was 64% for a xenon flow rate of 0.3 standard liters per hour (slh) or 5 sccm [27]. At higher flow rates, polarization remained remarkably high with output of 50% observed at 1.2 slh and 22% polarization at 6 slh.…”

Functional lung imaging using hyperpolarized gas MRI

“…However, recent advances in the design of optical pumping devices for efficient polarization of Xe-129 (45) and the wider availability and reduced cost of this gas make it a likely solution to the cost concerns. Moreover, Xe-129 has advantages for measuring both chemical and physical diffusion using MRI, as well as for T2-weighted acquisitions at lower field strengths.…”

“…In this method, depolarization is reduced by freezing the polarized nuclei in the solid state using a liquid N 2 cold finger (43,44). Recent breakthroughs using enriched Xe-129 have made polarization levels delivered to the subject comparable to those achieved with He-3 (45).…”

Functional Imaging: CT and MRI

“…(156) However, improvement in hyperpolarization systems has meant that 129-Xenon MR imaging is making rapid strides forward, giving new insight in lung function. (160)(161)(162).One of the main features of hyperpolarized gas imaging is that the signal introduced in the system is so high that imaging is less dependent on field strength than is the case for proton imaging, and this has advantages as lower field-strength magnets may result in fewer artifacts. (163)(164)(165) A main disadvantage to this technique is that the contrast is exogenous, and is non-renewable.…”