Enhancement of Xe-129 polarization by off-resonant spin exchange optical pumping

A high power narrow line width (38 W, 0.09 nm full width at half maximum) external cavity diode laser is investigated for rubidium spin exchange optical pumping of Xe-129. This tunable photon source has a constant line width, independent of operating power or wavelength within a 1 nm tuning range. When using this laser, an increase in the Xe-129 nuclear polarization is observed when optically pumping at a lower wavelength than the measured Rb electron D-1 absorption. The exact detuning from D1 for the highest polarization is dependent upon the gas density. Furthermore, at high power and/or high Rb density, a reduction in the polarization occurs at the optimum wavelength as previously reported in spin exchange optical pumping studies of He-3 which is consistent with high absorption close to the cell front face. These results are encouraging for moderate high throughput polarization of Xe-129 in the midpressure range of (0.5-2.0 amagat). (C) 2010 American Institute of Physics. [doi: 10.1063/1.3478707

Enhancement of Xe-129 polarization by off-resonant spin exchange optical pumping

A high power narrow line width (38 W, 0.09 nm full width at half maximum) external cavity diode laser is investigated for rubidium spin exchange optical pumping of Xe-129. This tunable photon source has a constant line width, independent of operating power or wavelength within a 1 nm tuning range. When using this laser, an increase in the Xe-129 nuclear polarization is observed when optically pumping at a lower wavelength than the measured Rb electron D-1 absorption. The exact detuning from D1 for the highest polarization is dependent upon the gas density. Furthermore, at high power and/or high Rb density, a reduction in the polarization occurs at the optimum wavelength as previously reported in spin exchange optical pumping studies of He-3 which is consistent with high absorption close to the cell front face. These results are encouraging for moderate high throughput polarization of Xe-129 in the midpressure range of (0.5-2.0 amagat). (C) 2010 American Institute of Physics. [doi: 10.1063/1.3478707

New disagreement metrics incorporating spatial detail – applications to lung imaging

Evaluation of medical image segmentation is increasingly important. While set-based agreement metrics are widespread, they assess the absolute overlap, but fail to account for any spatial information related to the differences or to the shapes being analyzed. In this paper, we propose a family of new metrics that can be tailored to deal with a broad class of assessment needs

Functional image-based radiotherapy planning for non-small cell lung cancer: a simulation study

Background and purpose: To investigate the incorporation of data from single-photon emission computed tomography (SPECT) or hyperpolarized helium-3 magnetic resonance imaging (He-3-MRI) into intensity-modulated radiotherapy (IMRT) planning for non-small cell lung cancer (NSCLC). Material and methods: Seven scenarios were simulated that represent cases of NSCLC with significant functional lung defects. Two independent IMRT plans were produced for each scenario; one to minimise total lung volume receiving >= 20 Gy (V-20), and the other to minimise only the functional lung volume receiving >= 20 Gy (FV20). Dose-volume characteristics and a plan quality index related to planning target volume coverage by the 95% isodose (V-PTV95/FV20) were compared between anatomical and functional plans using the Wilcoxon signed ranks test. Results: Compared to anatomical IMRT plans, functional planning reduced FV20 (median 2.7%, range 0.6-3.5%, p = 0.02), and total lung V-20 (median 1.5%, 0.5-2.7%, p = 0.02), with a small reduction in mean functional lung dose (median 0.4 Gy, 0-0.7 Gy, p = 0.03). There were no significant differences in target volume coverage or organ-at-risk doses. Plan quality index was improved for functional plans (median increase 1.4, range 0-11.8, p = 0.02). Conclusions: Statistically significant reductions in FV20, V-20 and mean functional lung dose are possible when IMRT planning is supplemented by functional information derived from SPECT or He-3-MRI. (C) 2009 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 93 (2009) 32-3

Imaging pathophysiological changes in the lungs in IPF with xenon magnetic resonance imaging

Editoria

Comparison of MEMS switches and PIN diodes for switched dual tuned RF coils

PURPOSE: To evaluate the performance of micro-electromechanical systems (MEMS) switches against PIN diodes for switching a dual-tuned RF coil between19F and1H resonant frequencies for multi-nuclear lung imaging. METHODS: A four-element fixed-phase and amplitude transmit-receive RF coil was constructed to provide homogeneous excitation across the lungs, and to serve as a test system for various switching methods. The MR imaging and RF performance of the coil when switched between the19F and1H frequencies using MEMS switches, PIN diodes and hardwired configurations were compared. RESULTS: The performance of the coil with MEMS or PIN diode switching was comparable in terms of RF measurements, transmit efficiency and image SNR on both19F and1H nuclei. When the coil was not switched to the resonance frequency of the respective nucleus being imaged, reductions in the transmit efficiency were observed of 32% at the19F frequency and 12% at the1H frequency. The coil provides transmit field homogeneity of ±12.9% at the1H frequency and ±14.4% at the19F frequency in phantoms representing the thorax with the air space of the lungs filled with perfluoropropane gas. CONCLUSION: MEMS and PIN diodes were found to provide comparable performance in on-state configuration, while MEMS were more robust in off-state high-powered operation (>1 kW), providing higher isolation and requiring a lower DC switching voltage than is needed for reverse biasing of PIN diodes. In addition, clear benefits of switching between the19F and1H resonances were demonstrated, despite the proximity of their Larmor frequencies

Feasibility of human lung ventilation imaging using highly polarized naturally abundant xenon and optimized three-dimensional steady-state free precession

Purpose To demonstrate the potential for high quality MRI of pulmonary ventilation using naturally abundant xenon (NAXe) gas. Methods MRI was performed at 1.5 Tesla (T) and 3 T on one healthy smoker and two healthy never-smokers. 129Xe gas was polarized to ∼25% using an in-house spin-exchange optical pumping polarizer fitted with a laser diode array with integrated volume holographic grating and optical train system. Volunteers inhaled 1 L of NAXe for an 8 to 15 s breathhold while MR images were acquired with full-lung coverage using a three-dimensional steady-state free precession sequence, optimized for maximum signal-to-noise ratio (SNR) at a given spatial resolution. For the purpose of image quality comparison, the MR acquisition was repeated at 1.5 T with 400 mL enriched xenon and 200 mL 3He. Results All NAXe lung images were of high quality, with mean SNRs of 25–40 (voxel 4.2 × 4.2 × 8/10 mm3) and ∼30% improvement at 3 T versus 1.5 T. The high SNR permitted identification of minor ventilation defects in the healthy smoker's lungs. NAXe images were of comparable SNR to those obtained with enriched xenon and 3He. Conclusion Optimization of MR pulse sequences and advances in polarization technology have facilitated high quality pulmonary ventilation imaging with inexpensive NAXe gas. Magn Reson Med 74:346–352, 2015

High resolution spectroscopy and chemical shift imaging of hyperpolarized 129 Xe dissolved in the human brain in vivo at 1.5 tesla

Purpose Upon inhalation, xenon diffuses into the bloodstream and is transported to the brain, where it dissolves in various compartments of the brain. Although up to five chemically distinct peaks have been previously observed in 129Xe rat head spectra, to date only three peaks have been reported in the human head. This study demonstrates high resolution spectroscopy and chemical shift imaging (CSI) of 129Xe dissolved in the human head at 1.5 Tesla. Methods A 129Xe radiofrequency coil was built in-house and 129Xe gas was polarized using spin-exchange optical pumping. Following the inhalation of 129Xe gas, NMR spectroscopy was performed with spectral resolution of 0.033 ppm. Two-dimensional CSI in all three anatomical planes was performed with spectral resolution of 2.1 ppm and voxel size 20 mm × 20 mm. Results Spectra of hyperpolarized 129Xe dissolved in the human head showed five distinct peaks at 188 ppm, 192 ppm, 196 ppm, 200 ppm, and 217 ppm. Assignment of these peaks was consistent with earlier studies. Conclusion High resolution spectroscopy and CSI of hyperpolarized 129Xe dissolved in the human head has been demonstrated. For the first time, five distinct NMR peaks have been observed in 129Xe spectra from the human head in vivo

Polymorphism in glutathione S-transferase P1 is associated with susceptibility to chemotherapyinduced leukemia

Glutathione S-transferases (GSTs) detoxify potentially mutagenic and toxic DNA-reactive electrophiles, including metabolites of several chemotherapeutic agents, some of which are suspected human carcinogens. Functional polymorphisms exist in at least three genes that encode GSTs, including GSTM1, GSTT1, and GSTP1. We hypothesize, therefore, that polymorphisms in genes that encode GSTs alter susceptibility to chemotherapy-induced carcinogenesis, specifically to therapy-related acute myeloid leukemia (t-AML), a devastating complication of long-term cancer survival. Elucidation of genetic determinants may help to identify individuals at increased risk of developing t-AML. To this end, we have examined 89 cases of t-AML, 420 cases of de novo AML, and 1,022 controls for polymorphisms in GSTM1, GSTT1, and GSTP1. Gene deletion of GSTM1 or GSTT1 was not specifically associated with susceptibility to t-AML. Individuals with at least one GSTP1 codon 105 Val allele were significantly over-represented in t-AML cases compared with de novo AML cases [odds ratio (OR), 1.81; 95% confidence interval (CI), 1.11–2.94]. Moreover, relative to de novo AML, the GSTP1 codon 105 Val allele occurred more often among t-AML patients with prior exposure to chemotherapy (OR, 2.66; 95% CI, 1.39–5.09), particularly among those with prior exposure to known GSTP1 substrates (OR, 4.34; 95% CI, 1.43–13.20), and not among those t-AML patients with prior exposure to radiotherapy alone (OR,1.01; 95% CI, 0.50–2.07). These data suggest that inheritance of at least one Val allele at GSTP1 codon 105 confers a significantly increased risk of developing t-AML after cytotoxic chemotherapy, but not after radiotherapy