e. 0.23 nm FWHM at 794.7 nm) [10]. Using stopped flow SEOP, the highest 129Xe polarization was found at pressures between 22 and 46 kPa depending on the mixture used as shown in Fig. 1. Similarly, the highest 83Kr polarization value for the various gas mixtures were found at a pressure range between 30 and 54 kPa. JQ1 in vitro In stopped flow SEOP, the gas mixture remains in the SEOP cell until a (near) steady state polarization is obtained, thus maximizing the obtained spin polarization. Note that the stopped flow mode is crucial for the production

of hp 83Kr for MRI applications. Furthermore, stopped flow SEOP opens up the possibility for a single extraction–compression cycle for the hp noble gases. In order to simplify comparison of the MR signal expected form diluted hp gas mixtures with that of concentrated hp 129Xe, the

apparent polarization, Papp, was defined for hp gas mixtures: equation(1) Papp=P·[NG]∑i[Mi]where the scaling of the spin polarization, P, is taken into account through the noble gas (number) density, [NG], divided by the overall (number) density of all components Mi in the mixture [10]. This definition is useful because Papp allows for easy comparison of the signal intensities from diluted hp noble gas mixtures – i.e. a dilute mixture with Papp = 10% results in the same NMR signal intensity as that of a pure hp noble gas with P = 10%. In the previous work, using 23 W of incident laser power, the highest apparent polarizations for hp 83Kr were found with the Papp=4.4±0.5%Papp=4.4±0.5% for the 25% krypton–75% N2 mixture and Papp=4.3±0.5%Papp=4.3±0.5% for the 50% krypton–50% www.selleckchem.com/products/Roscovitine.html N2 gas mixture. Higher and lower krypton concentration quickly leads to reduced apparent polarizations as shown in Fig. 1. Similarly, the highest 129Xe polarization was found for the 50% xenon–50% N2 mixture with Papp=15.5±1.9%Papp=15.5±1.9%. An apparent 129Xe polarization of Papp = 15.5% as shown in Fig. RG7420 mw 1 is sufficiently high to consider the cryogenics free hp 129Xe production for biomedical MRI applications. However, the cryogenic process

does not only facilitate gas separation, it usually also enables gas transport from the SEOP cell to a small volume cold finger during the freezing phase. Subsequent sublimation of the frozen hp 129Xe allows for recompression of the hp gas to ambient pressure or above. If this step is omitted, some other means of hp gas transportation needs to be instituted for low pressure SEOP. For simple polarization measurements the hp gas can be transferred through expansion from the SEOP cell through transfer tubing into a pre-evacuated sample cell for NMR detection at low pressures ( Fig. 2). This method was used in this work to provide baseline data and is therefore dubbed ‘Baseline Scheme’. However, for biomedical applications, such as lung MRI in an ambient pressure environment, the hp gas is required to be compressed before usage.