The situation is different for xenon. Due to its large compressible outer electron shell, 129Xe exhibits a significant chemical shift when placed into different chemical environments as compared to the gas phase. The 129Xe NMR chemical shift range is just below 300 ppm for the various materials and solvents that may absorb the xenon atoms [11], [12], [15] and [16]. Note, that 129Xe NMR signal in the bulk gas phase approximated to zero pressure is typically referenced with 0 ppm and the

shift increases by about of 0.6 ppm/bar in pure xenon gas at ambient temperature and pressure conditions close to ideal gas behavior. There is an extensive literature covering hyperpolarized DZNeP chemical structure 129Xe NMR spectroscopy in addition to work with thermally polarized 129Xe that utilizes the chemical shift as a

PLX4032 datasheet ‘spy’ for the environment of the xenon atoms. However, with the recent advances in hyperpolarization of this nucleus, the interrogation of dissolved xenon chemical shift has excellent perspectives for MRI applications in materials science and biomedical studies. 129Xe chemical shift selective imaging can be used to visualize the effects of gas transport in porous media [63] and [64]. In conventional MRI, the variation of the recycle delay can lead to T1 relaxation weighted contrast. In hp MRI, the variation of recycle delay may produce Temsirolimus chemical structure a gas transport weighted contrast if hp 129Xe is continuously delivered. The gas is hyperpolarized outside the superconducting magnet and its transport into the sample through flow and diffusion will take time. After a 90° excitation pulse,

all hp 129Xe within the detection region has been depolarized and the following scan will only detect any signal if the recycle delay is long enough to permit for renewed hp 129Xe delivery. This allows for the unique transport weighted contrast that provides a ‘snapshot’ of the gas penetration into porous samples as shown in Fig. 5. Note that the xenon concentration in the sample is constant in time but the ‘concentration’ of the hp nuclear spin state is time dependent. The application of depolarizing radiofrequency (RF) pulses requires that new hp gas is delivered into the material during the recycle delay. At constant recycle delays, a steady state is generated that can be imaged [64]. The chemical shift of 129Xe is also very useful for pulmonary MRI where continuous flow hp 129Xe transport is replaced by usage of the breathing cycle for delivery. When coupled with xenon’s high solubility, it is possible to record a distinct signal arising from xenon atoms associated only with parts of lungs where xenon dissolves, i.e. lung tissue and its components.