Gradient-Echo Imaging Considerations for Hyperpolarized129Xe MR

Zhao, Lei; Mulkern, Robert V.; Tseng, Ching-Hsiang; Williamson, Daniel; Patz, Samuel; Kraft, Robert A.; Walsworth, Ronald L.; Jólesz, Ferenc A.; Albert, Mitchell S.

doi:10.1006/jmrb.1996.0173

Cited by 192 publications

(216 citation statements)

References 10 publications

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“…We hypothesize that with centric or half-Fourier phase encoding a higher flip angle can be used, with an inherent increase in SNR. This substantiates the qualitative observations reported by other groups that used centric ordering in morphologic imaging studies (17,19,20). Applications that will benefit from this approach include thin-slice 2D experiments, which requires a more precise knowledge of the slice integrity than that attainable using thick slices or the non-slice-selective projection approaches in the literature (4 -6,10,11).…”

Section: Discussionsupporting

confidence: 83%

“…If we assume short repetition times (TRs), such that longitudinal relaxation can be ignored, i.e., nTR ϽϽ T 1 for gaseous 3 He, and a spoiling of residual transverse magnetization following acquisition, then the transverse magnetization M y , tipped in to the xy plane by the nth RF excitation is well approximated by M 0 (cos ) n-1 sin , where M 0 represents the initial hyperpolarized longitudinal magnetization and a rotation about the -x axis (17,21,22). An indication of the SNR in the reconstructed image is the amplitude of this magnetization evaluated at the central k-space point.…”

Section: Theorymentioning

confidence: 99%

“…Mugler (16) referred to the potential k-space filtering effects of a diminishing polarization. In a qualitative study, Zhao et al (17) compared SNR and the resolution of boundaries of images of sealed cells of hyperpolarized 129 Xe acquired with sequential and centric phase-encoding strategies. Chawla et al (19) made a similar qualitative comparison of the influence of phase-encoding strategies on the SNR of in vitro images of samples of 3 He encapsulated in microspheres.…”

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confidence: 99%

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k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized ³He MRI: Spatial resolution and signal‐to‐noise ratio considerations

Wild

Paley

Viallon

et al. 2002

Magnetic Resonance in Med

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In this work some of the factors that can influence the signal-tonoise ratio (SNR) and spatial resolution in MR images of inhaled hyperpolarized gases are systematically addressed. In particular, the effects of RF depletion of longitudinal polarization and image gradient diffusion dephasing were assessed in terms of their contribution to a k-space filter. By means of theoretical simulations and a novel method of experimental validation using a variable transverse magnetization of the 1 H signal, systematic quantitative and qualitative investigations of the effects of k-space filtering intrinsic to imaging of hyperpolarized gas were made. A 2D gradient-echo image is considered for a range of flip angles with centric, sequential, and half-Fourier Cartesian phase-encoding strategies, and the results are assessed in terms of SNR and spatial resolution in the reconstructed images. Centric phase encoding was found to give the best SNR at higher flip angles, with a trade-off in spatial resolution compared to sequential phase encoding. A half-Fourier approach potentially offers increased SNR through the use of higher flip angles without compromising the spatial resolution, which is comparable to that achieved with sequential encoding. Magn Reson Med 47:687-695, 2002.

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Section: Discussionsupporting

confidence: 83%

Section: Theorymentioning

confidence: 99%

mentioning

confidence: 99%

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k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized ³He MRI: Spatial resolution and signal‐to‐noise ratio considerations

Wild

Paley

Viallon

et al. 2002

Magnetic Resonance in Med

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“…More rapid methods have been recently proposed that are capable of measuring center frequency and flip angle without the need for a separate test-dose scan (58). Interesting approaches to maximizing SNR also have been proposed using a variable flip angle technique in which the flip angle is increased with each TR so as to consume all the available longitudinal magnetization during the acquisition (59,60).…”

Section: Rf Excitation and Signal Calibrationmentioning

confidence: 99%

Functional lung imaging using hyperpolarized gas MRI

Fain

Korosec

Holmes

et al. 2007

Magnetic Resonance Imaging

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158

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The noninvasive assessment of lung function using imaging is increasingly of interest for the study of lung diseases, including chronic obstructive pulmonary disease (COPD) and asthma. Hyperpolarized gas MRI (HP MRI) has demonstrated the ability to detect changes in ventilation, perfusion, and lung microstructure that appear to be associated with both normal lung development and disease progression. The physical characteristics of HP gases and their application to MRI are presented with an emphasis on current applications. Clinical investigations using HP MRI to study asthma, COPD, cystic fibrosis, pediatric chronic lung disease, and lung transplant are reviewed. Recent advances in polarization, pulse sequence development for imaging with Xe-129, and prototype low magnetic field systems dedicated to lung imaging are highlighted as areas of future development for this rapidly evolving technology.

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“…This dictates that all HHe signals have an inherent T 1 and flip angle weighting. Thus, the detected signal from a series of n RF pulses of constant flip angle ( ), constant TE, and constant TR for a HHe diffusion experiment is given by (19):…”

Section: T 1 and Flip Angle-related Attenuation Correctionmentioning

confidence: 99%

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

Shanbhag

Altes

Miller

et al. 2006

Magnetic Resonance Imaging

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Purpose:To examine the utility of a 3 He spectroscopic q-space technique for detecting changes in lung morphometry in vivo. Materials and Methods:A diffusion-weighted spectroscopy sequence was used to collect global diffusion data from healthy adults (N ϭ 11), healthy children (N ϭ 5), and chronic obstructive pulmonary disease (COPD) patients (N ϭ 2) using 40 cc of hyperpolarized 3 He gas within a two second breathhold. Displacement probability profiles (DPP) were obtained by Fourier transformation of diffusion data with respect to q. A bi-Gaussian model was used to decompose the DPPs into narrow and broad components, characterized by root-mean-square displacements X rms1 and X rms2 , respectively. Results:In healthy adults, the narrow component (X rms,1 ) of the DPP had a mean displacement of 188 Ϯ 10 m, slightly less than the reported average size of the alveoli. The broad component (X rms,2 ) had a mean value of 474 Ϯ 44 m, comparable to the diameter of the respiratory bronchioles in the acinus. In children, both X rms1 (167 Ϯ 4 m) and X rms2 (382 Ϯ 22 m) compared to healthy adults (P Ͻ 0.01). In COPD patients, the mean displacements were elevated (X rms1 : 265 Ϯ 71 m; X rms2 : 530 Ϯ 109 m) compared to healthy adults. Excellent correlation was found between rms displacements and age (age vs. X rms,1 : r ϭ 0.78, P Ͻ 0.001; age vs. X rms,2 : r ϭ 0.90, P Ͻ 0.001). Conclusion:The q-space parameters agreed remarkably well with published alveolar morphometry data. The results suggest that the technique may be sensitive to disease, as evident from the elevated mean displacements in COPD patients compared to healthy volunteers. Detailed lung microstructural information can be obtained using a very low volume of inhaled 3 He.

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Gradient-Echo Imaging Considerations for Hyperpolarized129Xe MR

Cited by 192 publications

References 10 publications

k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized ³He MRI: Spatial resolution and signal‐to‐noise ratio considerations

k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized ³He MRI: Spatial resolution and signal‐to‐noise ratio considerations

Functional lung imaging using hyperpolarized gas MRI

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

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Gradient-Echo Imaging Considerations for Hyperpolarized129Xe MR

Cited by 192 publications

References 10 publications

k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized 3He MRI: Spatial resolution and signal‐to‐noise ratio considerations

k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized 3He MRI: Spatial resolution and signal‐to‐noise ratio considerations

Functional lung imaging using hyperpolarized gas MRI

q‐space analysis of lung morphometry in vivo with hyperpolarized3He spectroscopy

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Product

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k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized ³He MRI: Spatial resolution and signal‐to‐noise ratio considerations

k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized ³He MRI: Spatial resolution and signal‐to‐noise ratio considerations

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy