@article {257, title = {Band-selective chemical exchange saturation transfer imaging with hyperpolarized xenon-based molecular sensors}, journal = {Journal of Magnetic Resonance}, volume = {213}, year = {2011}, note = {J Magn Reson847UKTimes Cited:3Cited References Count:29}, month = {Dec}, pages = {14-21}, abstract = {

Molecular imaging based on saturation transfer in exchanging systems is a tool for amplified and chemically specific magnetic resonance imaging. Xenon-based molecular sensors are a promising category of molecular imaging agents in which chemical exchange of dissolved xenon between its bulk and agent-bound phases has been use to achieve sub-picomolar detection sensitivity. Control over the saturation transfer dynamics, particularly when multiple exchanging resonances are present in the spectra, requires saturation fields of limited bandwidth and is generally accomplished by continuous wave irradiation. We demonstrate instead how band-selective saturation sequences based on multiple pulse inversion elements can yield saturation bandwidth tuneable over a wide range, while depositing less RF power in the sample. We show how these sequences can be used in imaging experiments that require spatial-spectral and multispectral saturation. The results should be applicable to all CEST experiments and, in particular, will provide the spectroscopic control required for applications of arrays of xenon chemical sensors in microfluidic chemical analysis devices. (C) 2011 Elsevier Inc. All rights reserved.

}, keywords = {xe-129}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2011.06.027}, url = {://WOS:000296997800002}, author = {Meldrum, T. and Bajaj, V. S. and Wemmer, D. E. and Pines, A.} } @article {261, title = {MRI Thermometry Based on Encapsulated Hyperpolarized Xenon}, journal = {Chemphyschem}, volume = {11}, year = {2010}, note = {Chemphyschem691LFTimes Cited:2Cited References Count:25}, month = {Nov 15}, pages = {3529-3533}, abstract = {

A new approach to MRI thermometry using encapsulated hyperpolarized xenon is demonstrated The method is based on the temperature dependent chemical shift of hyperpolarized xenon in a cryptophane-A cage This shift is linear with a slope of 029 ppm degrees C(-1) which is perceptibly higher than the shift of the proton resonance frequency of water (ca 0 01 ppm degrees C(-1)) that is currently used for MRI thermometry Using spectroscopic imaging techniques, we collected temperature maps of a phantom sample that could discriminate by direct NMR detection between temperature differences of 0 1 degrees C at a sensor concentration of 150 mu M Alternatively, the xenon-in-cage chemical shift was determined by indirect detection using saturation transfer techniques (Hyper-CEST) that allow detection of nanomolar agent concentrations Thermometry based on hyperpolarized xenon sensors improves the accuracy of currently available MRI thermometry methods, potentially giving rise to biomedical applications of biosensors functionalized for binding to specific target molecules

}, keywords = {xe-129}, isbn = {1439-4235}, doi = {Doi 10.1002/Cphc.201000507}, url = {://WOS:000285080600023}, author = {Schilling, F. and Schroder, L. and Palaniappan, K. K. and Zapf, S. and Wemmer, D. E. and Pines, A.} } @article {342, title = {Inclusion complexes oriented in thermotropic liquid-crystalline solvents studied with carbon-13 NMR}, journal = {Journal of Physical Chemistry B}, volume = {107}, year = {2003}, note = {J Phys Chem B743MATimes Cited:11Cited References Count:19}, month = {Nov 20}, pages = {12558-12561}, abstract = {

The inclusion complex of cryptophane-A and chloroform dissolved in two nonchiral liquid-crystalline environments was investigated via C-13 NMR. Stable solutions of oriented complexes were prepared using aromatic (ZLI 1132) and aliphatic (ZLI 1695) thermotropic nematic liquid crystals as solvents; ordering of the complexes was manifested by the H-1-C-13 dipolar splitting of the C-13 resonance of labeled chloroform. In both solutions, the dipolar splitting for the bound ligands was substantially larger than that obtained for the free ligands, indicating a significant increase in ligand ordering upon complexation despite the absence of direct contact with the oriented solvent molecules. A similar enhancement in ordering was observed for complexed ligands compared to that for free ligands in both liquid-crystalline solvents. Also, the application of heteronuclear decoupling to the ZLI 1695 solution resulted in a reduced line width for the bound C-13 chloroform resonance, suggesting that a significant component of the observed line broadening may originate from intermolecular couplings between host and guest molecules. These results demonstrate the potential for using restored dipolar couplings to investigate structural and dynamical aspects of inclusion complexes in solution.

}, keywords = {xe-129}, isbn = {1520-6106}, doi = {Doi 10.1021/Jp030431e}, url = {://WOS:000186574500003}, author = {Marjanska, M. and Goodson, B. M. and Castiglione, F. and Pines, A.} } @article {393, title = {Effects of diffusion on magnetic resonance imaging of laser-polarized xenon gas}, journal = {Journal of Chemical Physics}, volume = {108}, year = {1998}, note = {J Chem PhysZh114Times Cited:30Cited References Count:24}, month = {Apr 15}, pages = {6233-6239}, abstract = {

Molecular diffusion during the application of magnetic field gradients can distort magnetic resonance images. A systematic characterization of these distortions in one dimension was performed using highly spin-polarized xenon gas. By varying the strength of the applied gradient and the geometric dimension of the sample, the evolution of these image distortions between the regimes of strong and weak diffusion was observed. These results are compared with numerical simulations. By directly measuring the displacement distribution of the polarized xenon atoms, it is shown that in the weak-diffusion regime the image distortions originate from the restricted diffusive motion near the sample boundaries, in agreement with previous theoretical work. Additionally, it is shown that the effects of diffusion can be utilized to enhance the contrast between the boundaries and bulk in the images of polarized gas samples, and thus may be exploited as a means of boundary detection in such systems. (C) 1998 American Institute of Physics. [S0021-9606(98)02915-8].

}, keywords = {xe-129}, isbn = {0021-9606}, doi = {Doi 10.1063/1.476030}, url = {://WOS:000073073700018}, author = {Song, Y. Q. and Goodson, B. M. and Sheridan, B. and de Swiet, T. M. and Pines, A.} } @article {410, title = {Optical magnetic resonance imaging of Rb vapor in low magnetic fields}, journal = {Physics Letters A}, volume = {226}, year = {1997}, note = {Phys Lett AWf939Times Cited:12Cited References Count:19}, month = {Feb 10}, pages = {69-74}, abstract = {

By applying magnetic field gradients to alkali vapor cells, images of the spatial distribution of spin-polarized Rb atoms were obtained. Optical pumping is used to produce precessing spin-polarization in the ground state. Detection of the coherent spin transients is performed in the time-domain by a single optical probe beam covering the whole sample cell. Spatial resolution of better than 1 mm has been achieved by a projection-reconstruction method.

}, keywords = {xe-129}, isbn = {0375-9601}, doi = {Doi 10.1016/S0375-9601(96)00927-9}, url = {://WOS:A1997WF93900012}, author = {Skalla, J. and Wackerle, G. and Mehring, M. and Pines, A.} }