Graham Norquay

Simultaneous Imaging of Lung Structure and Function with Triple-Nuclear Hybrid MR Imaging

PURPOSE To re-engineer a standard clinical magnetic resonance (MR) imaging system to enable the acquisition, in the same breath hold, of lung images from two hyperpolarized gases (helium 3 [(3)He] and xenon 129 [(129)Xe]) with simultaneous registered anatomic proton (hydrogen 1 [(1)H]) MR images of lung structure. MATERIALS AND METHODS Studies with (3)He and (129)Xe were performed with National Research Ethics Committee approval, with informed consent from the volunteer. (1)H-(3)He-(129)Xe MR imaging was achieved in the same breath by using mutually decoupled nested radiofrequency coil hardware capable of transmit and receive on each respective nucleus without power cross talk. MR pulse sequences were also developed for rapid switching between each nucleus. The system is demonstrated with triple-nuclear lung images in a healthy individual following inhalation of a mixture of (3)He and (129)Xe gases. RESULTS Spatially and temporally registered images of all three nuclei were obtained with high signal to noise ratio and high spatial resolution in the same breath. CONCLUSION The multinuclear technique is capable of providing registered lung images with mutually complementary functional and structural spatial information.

Optimized production of hyperpolarized 129Xe at 2 bars for in vivo lung magnetic resonance imaging

In this work, the production rate of a spin-exchange optical pumping 129Xe gas polarizer was optimized for routine generation of hyperpolarized 129Xe for in vivo lung MRI. This system uses a narrow (∼ 0.1 nm linewidth), tuneable external cavity laser (operating at ∼25 W) for SEOP of 3% gas mixtures of Xe inside a mid-pressure (2 bars) cell of 491 cm3 volume. Under this regime, theoretical and experimentally measured 129Xe polarizations were calculated to be 24% and 12%, respectively, for a gas flow rate of 300 sccm and a cell temperature of 373 K. The photon efficiency was evaluated, yielding theoretical and experimental values of 0.039 and 0.046, respectively. The theoretical efficiency was calculated from spin-exchange and spin-destruction cross sections and the experimental photon efficiency was measured under flow for a gas-cell residency time equal to an empirically determined spin-exchange time of 45 s. In addition, details of the Xe freeze-out process were analyzed with a model of polarization deca...

Experimental validation of the hyperpolarized (129) Xe chemical shift saturation recovery technique in healthy volunteers and subjects with interstitial lung disease.

To assess the sensitivity of the hyperpolarized 129Xe chemical shift saturation recovery (CSSR) technique for noninvasive quantification of changes to lung microstructure and function in idiopathic pulmonary fibrosis (IPF) and systemic sclerosis (SSc).

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

To demonstrate the potential for high quality MRI of pulmonary ventilation using naturally abundant xenon (NAXe) gas.

Hyperpolarized 129Xe gas lung MRI–SNR and T2* comparisons at 1.5 T and 3 T

In this study, the signal‐to‐noise ratio of hyperpolarized 129Xe human lung magnetic resonance imaging was compared at 1.5 T and 3 T. Experiments were performed at both B0 fields with quadrature double Helmholtz transmit–receive chest coils of the same geometry with the same subject loads. Differences in sensitivity between the two field strengths were assessed from the signal‐to‐noise ratio of multi‐slice 2D 129Xe ventilation lung images obtained at the two field strengths with a spatial resolution of 15 mm × 4 mm × 4 mm. There was a systematically higher signal‐to‐noise ratio observed at 3 T than at 1.5 T by a factor of 1.25. Mean image signal‐to‐noise ratio was in the range 27–44 at 1.5 T and 36–51 at 3 T. T  2* of 129Xe gas in the partially inflated lungs was measured to be 25 ms and 18 ms at 1.5 T and 3 T, respectively. T  2* of 129Xe gas in fully inflated lungs was measured to be 52 ms and 24 ms at 1.5 T and 3 T, respectively. Magn Reson Med, 2012.

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

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.

Relaxation and exchange dynamics of hyperpolarized 129Xe in human blood

129Xe‐blood NMR was performed over the full blood oxygenation range to evaluate 129Xe relaxation and exchange dynamics in human blood.

Radiofrequency pulse design for the selective excitation of dissolved 129Xe

To optimize radiofrequency (RF) pulses for the selective excitation of dissolved phase 129Xe that take into account the very short T2*, while simultaneously, minimally exciting the much larger gas signal.

Lung ventilation volumetry with same-breath acquisition of hyperpolarized gas and proton MRI.

The purpose of this work was to assess the reproducibility of percentage of ventilated lung volume (PV) measured from hyperpolarized (HP) 3He and 1H anatomical images acquired in the same breath‐hold when compared with PV measured from 3He and 1H images from separate breath‐holds.

Detection of early sub-clinical lung disease in children with cystic fibrosis by lung ventilation imaging with hyperpolarized gas MRI

Hyperpolarised 3He ventilation-MRI, anatomical lung MRI, lung clearance index (LCI), low-dose CT and spirometry were performed on 19 children (6–16 years) with clinically stable mild cystic fibrosis (CF) (FEV1>−1.96), and 10 controls. All controls had normal spirometry, MRI and LCI. Ventilation-MRI was the most sensitive method of detecting abnormalities, present in 89% of patients with CF, compared with CT abnormalities in 68%, LCI 47% and conventional MRI 22%. Ventilation defects were present in the absence of CT abnormalities and in patients with normal physiology, including LCI. Ventilation-MRI is thus feasible in young children, highly sensitive and provides additional information about lung structure–function relationships.