Operating characteristics of hyperpolarized ³He and arterial spin tagging in MR imaging of ventilation and perfusion in healthy subjects

Rationale and Objectives. The authors tested the feasibility of a magnetic resonance (MR) imaging method combining the use of hyperpolarized helium 3 (³He) for ventilation imaging and an arterial spin-tagging sequence for perfusion imaging in six healthy human subjects. Materials and Methods. High-resolution sagittal images depicting ³He distribution were acquired after the subjects' inhalation of 500 mL of laser-hyperpolarized ³He produced by spin-exchange optical pumping. Perfusion MR imaging was performed with a steady-state arterial spin-tagging sequence that enabled the acquisition of three-dimensional images of pulmonary perfusion without the need for subject breath holding. Results. The ³He ventilation images display, with high signal intensity and detailed anatomic localization, the airspace of the lung parenchyma. The signal intensity on the perfusion images decreased by 23.2% with the use of arterial spin tagging. Ventilation and perfusion were matched, as is expected in healthy subjects. Conclusion. This method may have important applications in the assessment of lung function, enabling the calculation of regional ventilation-perfusion ratios. It may also aid in the selection of candidates for lung volume-reduction surgery.