We have recently made extraordinary progress in exploiting new 129Xenon delivery routes to add perfusion information to the high-resolution ventilation images we produce. Historically this was limited to 2D imaging, but with a recent breakthrough in continuous 129Xe vascular infusion, we have now succeeded in 3D imaging of pulmonary perfusion and gas exchange in rats. This work has led to a presentation at the 2011 19th annual meeting of the International Society of Magnetic Resonance in Medicine (ISMRM), May 7-13, Montreal: Cleveland ZI, Moller HE, Hedlund LW, Nouls J, Freeman M, Qi Y, Driehuys B. 3D imaging of pulmonary ventilation and perfusion in rats using hyperpolarized 129Xe, Abstract 4548.
Proper matching of ventilation (V) and pulmonary perfusion (Q) is essential for efficient gas exchange. Moreover, mismatches between V and Q and spatial heterogeneity in the V/Q ratio are hallmarks of virtually all pulmonary diseases. Unfortunately, available methods of imaging V and Q in small animals: a) lack 3D resolution, which is needed to measure V/Q heterogeneity; b) employ multiple modalities or contrast agents, which complicates data quantification; or c) require hour-long image acquisitions, which prevent monitoring acute changes in V/Q. Potentially, these problems can be avoided using hyperpolarized 129Xe, which can generate lung images that reflect either ventilation or perfusion if delivered via the vasculature [Driehuys et al. Radiology 252, 386-93, 2009 Free PMC article]. To exploit these unique properties, we previously introduced a method of continuously infusing 129Xe to the blood using an extracorporeal (EC) circuit [Moller et al. Proc ISMRM 2009]. We demonstrated that EC infusion can be used to generate 3D images of pulmonary perfusion.
(A) Schematic depicting the extracorporeal (EC) infusion of hyperpolarized (HP) 129Xe in a rat.
- 129Xe gas flows from a reservoir within a pressurized cylinder into the gas exchange module where it is infused into the venous blood.
- Simultaneously, blood is drawn from the carotid artery, passed through the exchange module, and returned to the rat via the jugular vein.
- 129Xe then diffuses from the capillary blood into the adjacent alveolar airspaces.
(B) Axial slice from an EC infusion image.
(C) Corresponding ventilation image slice.
(D) 3D EC infusion image (color) overlaid on the 3D ventilation image (grayscale).
- The 2 images show good spatial agreement, but moderate heterogeneity is observed in the EC infusion image, which is consistent with normal variability in perfusion.