Neil J. Stewart

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.

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.

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.

Whole lung morphometry with 3D multiple b-value hyperpolarized gas MRI and compressed sensing

To demonstrate three‐dimensional (3D) multiple b‐value diffusion‐weighted (DW) MRI of hyperpolarized 3He gas for whole lung morphometry with compressed sensing (CS).

129 Xe chemical shift in human blood and pulmonary blood oxygenation measurement in humans using hyperpolarized 129 Xe NMR

To evaluate the dependency of the 129Xe‐red blood cell (RBC) chemical shift on blood oxygenation, and to use this relation for noninvasive measurement of pulmonary blood oxygenation in vivo with hyperpolarized 129Xe NMR.

Hyperpolarized (13) C,(15) N2 -Urea MRI for assessment of the urea gradient in the porcine kidney.

A decline in cortico‐medullary osmolality gradient of the kidney may serve as an early indicator of pathological disruption of the tubular reabsorption process. The purpose of this study was to investigate the feasibility of hyperpolarized 13C,15N2‐urea MRI as a biomarker of renal function in healthy porcine kidneys resembling the human physiology.

Observation of cardiogenic flow oscillations in healthy subjects with hyperpolarized 3He MRI

Recently, dynamic MRI of hyperpolarized (3)He during inhalation revealed an alternation of the image intensity between left and right lungs with a cardiac origin (Sun Y, Butler JP, Ferrigno M, Albert MS, Loring SH. Respir Physiol Neurobiol 185: 468-471, 2013). This effect is investigated further using dynamic and phase-contrast flow MRI with inhaled (3)He during slow inhalations (flow rate ∼100 ml/s) to elucidate airflow dynamics in the main lobes in six healthy subjects. The ventilation MR signal and gas inflow in the left lower lobe (LLL) of the lungs were found to oscillate clearly at the cardiac frequency in all subjects, whereas the MR signals in the other parts of the lungs had a similar oscillatory behavior but were smaller in magnitude and in anti-phase to the signal in the left lower lung. The airflow in the main bronchi showed periodic oscillations at the frequency of the cardiac cycle. In four of the subjects, backflows were observed for a short period of time of the cardiac cycle, demonstrating a pendelluft effect at the carina bifurcation between the left and right lungs. Additional (1)H structural MR images of the lung volume and synchronized ECG recording revealed that maximum inspiratory flow rates in the LLL of the lungs occurred during systole when the corresponding left lung volume increased, whereas the opposite effect was observed during diastole, with gas flow redirected to the other parts of the lung. In conclusion, cardiogenic flow oscillations have a significant effect on regional gas flow and distribution within the lungs.