Human Pulmonary Imaging and Spectroscopy with Hyperpolarized 129Xe at 0.2T

Patz, Samuel; Muradian, Iga; Hrovat, Mirko I.; Ruset, Iulian C.; Topulos, George P.; Covrig, S.; Frederick, Eric; Hatabu, Hiroto; Hersman, F. W.; Butler, James P.

doi:10.1016/j.acra.2008.01.008

Cited by 132 publications

(150 citation statements)

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“…While in conventional proton MRI the signal-to-noise ratio (SNR) increases with higher B 0 field strength, the influence of B 0 on imaging of hyperpolarized species is less obvious (1), and imaging at low field strengths becomes feasible and possibly preferable due to longer transverse relaxation times (2)(3)(4)(5).…”

mentioning

confidence: 99%

Susceptibility effects in hyperpolarized ³He lung MRI at 1.5T and 3T

Deppe

Parra‐Robles

Ajraoui

et al. 2009

Magnetic Resonance Imaging

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Purpose:To compare susceptibility effects in hyperpolarized 3 He lung MRI at the clinically relevant field strengths of 1.5T and 3T. Materials and Methods:Susceptibility-related B 0 inhomogeneity was evaluated on a macroscopic scale by B 0 field mapping via phase difference. Subpixel susceptibility effects were quantified by mapping T * 2 . Comparison was made between ventilation images obtained from the same volunteers at both field strengths. Results:The B 0 maps at 3T show enhanced off-resonance effects close to the diaphragm and the ribs due to susceptibility differences. The average T * 2 from a voxel (20 ϫ 4 ϫ 4) mm 3 was determined as T * 2 ϭ 27.8 msec Ϯ 1.2 msec at 1.5T compared to T * 2 ϭ 14.4 msec Ϯ 2.6 msec at 3T. In ventilation images the most prominent effect is increased signal attenuation close to the intrapulmonary blood vessels at higher B 0 . Conclusion:Image homogeneity and T * 2 are lower at 3T due to increased B 0 inhomogeneity as a consequence of susceptibility differences. These findings indicate that 3 He imaging at 3T has no obvious benefit over imaging at 1.5T, as signal-to-noise ratio (SNR) was comparable for both fields in this work. IN MRI OF HYPERPOLARIZED NUCLEI the contribution of the Boltzmann polarization, which depends on the field strength (B 0 ) of the static magnetic field, to the longitudinal magnetization is negligible, with the nuclear polarization governed by the external (hyper)polarization physics. While in conventional proton MRI the signal-to-noise ratio (SNR) increases with higher B 0 field strength, the influence of B 0 on imaging of hyperpolarized species is less obvious (1), and imaging at low field strengths becomes feasible and possibly preferable due to longer transverse relaxation times (2-5).Nevertheless, the current trend for multinuclear MR development on whole-body scanners is toward field strengths Ն3T, driven by the need for improved SNR in new applications of low-abundance nuclei such as 13 C and 23 Na. As a consequence, imaging of hyperpolarized nuclei at 3T is emerging (6,7), and there is the need to evaluate the performance at this field strength.In addition to its influence on SNR (1,8), the B 0 field strength has an effect on the field homogeneity via localized magnetic susceptibility differences both on a microscopic (subpixel) and macroscopic (larger than pixel) length scale. The susceptibility difference between lung tissue and air is on the order of ⌬ Ϸ 9 ppm (9). Susceptibility-related field gradients have a bearing on image appearance and the local effective transverse relaxation time T * 2 measured over a given voxel size. Previously, susceptibility effects in 3 He lung MRI at different field strengths have been studied by ramping down a 1.5T scanner to 0.54T (10), and a method to compensate for susceptibility artifacts in gradient-echo imaging at 1.5T has been proposed (11).In this work the influence of susceptibility differences between tissue and gas spaces in 3 He lung imaging at 1.5T and 3T was studied on the macroscopic scale by empl...

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mentioning

confidence: 99%

Susceptibility effects in hyperpolarized ³He lung MRI at 1.5T and 3T

Deppe

Parra‐Robles

Ajraoui

et al. 2009

Magnetic Resonance Imaging

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“…This phenomenon has been observed previously at field strengths of 0.2 T (6) in humans and at 4.7 T (35) in guinea pigs. Patz et al (6) hypothesized that this enhanced spin-spin relaxation is due to slow exchange of the 129 Xe with one or more of the dissolved phases. This hypothesis is supported by the observation of multiple spin-spin relaxation components in the present study.…”

Section: Discussionmentioning

confidence: 99%

“…Although most previous studies have employed 3 He due to its higher signal-to-noise ratio (SNR), 3 He has a very low natural abundance, making it a poor candidate for widespread clinical use. Conversely, 129 Xe gas has the advantage over 3 He of being more abundant in the atmosphere and therefore relatively inexpensive compared with 3 He (6). 129 Xe is also highly soluble in blood and displays an exquisite sensitivity to its local environment through a broad range of chemical shift and relaxation effects.…”

Section: Introductionmentioning

confidence: 99%

“…This means that the SNR in a HNG experiment is substantial at the low field strengths for which Eq. 2 holds true, which motivates the application of low magnetic field strength systems to perform HNG studies of p A O 2 using R 2,CPMG (6,(25)(26)(27)(28). CPMG spin-spin relaxation rate measurements of hyperpolarized 3 He at a field strength of 3 mT have recently been performed in human lungs (26) with corresponding T 2 relaxation times of sec.…”

Section: Introductionmentioning

confidence: 99%

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Measurement of alveolar oxygen partial pressure in the rat lung using Carr‐Purcell‐Meiboom‐Gill spin–spin relaxation times of hyperpolarized ³He and ¹²⁹Xe at 74 mT

Kraayvanger

Bidinosti

Dominguez‐Viqueira

et al. 2010

Magnetic Resonance in Med

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Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, 3 He and 129 Xe, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin-spin relaxation rate (R 2 ) of 3 He at low magnetic field strengths (<0.1 T) in vivo. R 2 measurements can be achieved efficiently using the Carr-Purcell-Meiboom-Gill pulse sequence. In this work, alveolar oxygen partial pressure measurements based on Carr-PurcellMeiboom-Gill R 2 values of hyperpolarized 3 He and 129 Xe in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin-spin relaxivity constants for 3 He and 129 Xe were determined to be (5.2 6 0.6) 310 26 Pa 21 sec 21 and (7.3 6 0.4) 310 26 Pa 21 s 21 compared with spin-lattice relaxivity constants of (4.0 6 0.4) 310 26 Pa 21 s 21 and (4.3 6 1.3) 3 10 26 Pa 21 s 21 , respectively. In vivo experimental measurements of alveolar oxygen partial pressure using 3 He in whole rat lung show good agreement (r 2 5 0.973) with predictions based on lung volumes and ventilation parameters. For 129 Xe, multicomponent relaxation was observed with one component exhibiting an increase in R 2 with decreasing alveolar oxygen partial pressure. Magn Reson Med 64:1484-1490,

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“…It has been reported that several physiological quantities related to these processes were globally evaluated from measurements of alveolar gas uptake dynamics using CSSR in animals 30,[42][43][44][45] and humans. 39,46,47 Whole-lung spectroscopy, however, limits the assessments to be accepted as global measures without any information about the spatial distribution in the lung. An extension of spectroscopybased methods to imaging-based methods is an important step toward identifying a region with impaired function with higher sensitivity and evaluation of its variation in the whole lung.…”

Section: Dissolved-phase 129 Xe Mrimentioning

confidence: 99%