Indirect detection of lung perfusion using susceptibility‐based hyperpolarized gas imaging

Abstract

To address the problem of inadequate signal-to-noise ratio (SNR) encountered in lung perfusion magnetic resonance imaging (MRI) by developing an indirect detection based on the strong hyperpolarized (HP) gas signal. Our model is based on detecting the effects of gadolinium (Gd) flowing through lung capillaries by recording the phase of the nearby alveolar HP gas. In a HP gas 3He phantom we imaged gas phases before and after removing tubes containing paramagnetic solution away from the phantom. We also imaged HP gas phases in pig lungs before and after injection of Gd. Finally, parenchymal spin phase in excised lungs was measured as a function of Gd concentration. In the phantom, the differential phase map displayed a pattern characteristic of a susceptibility-induced dipole field, showing the possibility of an indirect detection. In vivo, the differential phase map showed homogeneous appearance, as expected for uniform perfusion in healthy lungs. Ex vivo, the parenchymal spin phases were shown to depend linearly on Gd concentration. Our method should allow indirect perfusion (Q) and direct ventilation (V) to be assessed simultaneously, thus allowing for diagnosis of V/Q mismatches. The linear dependency of parenchymal spin phase vs. Gd concentration may allow for quantification of lung perfusion.