Abnormalities in hyperpolarized (129)Xe magnetic resonance imaging and spectroscopy in two patients with pulmonary vascular disease

Abstract

The diagnosis of pulmonary vascular disease (PVD) is usually based on hemodynamic and/or clinical criteria. Noninvasive imaging of the heart and proximal vasculature can also provide useful information. An alternate approach to such criteria in the diagnosis of PVD is to image the vascular abnormalities in the lungs themselves. Hyperpolarized (HP) (129)Xe magnetic resonance imaging (MRI) is a novel technique for assessing abnormalities in ventilation and gas exchange in the lungs. We applied this technique to two patients for whom there was clinical suspicion of PVD. Two patients who had significant hypoxemia and dyspnea with no significant abnormalities on computed tomography imaging or ventilation-perfusion scan and only mild or borderline pulmonary arterial hypertension at catheterization were evaluated. They underwent HP (129)Xe imaging and subsequently had tissue diagnosis obtained from lung pathology. In both patients, HP (129)Xe imaging demonstrated normal ventilation but markedly decreased gas transfer to red blood cells with focal defects on imaging, a pattern distinct from those previously described for idiopathic pulmonary fibrosis or obstructive lung disease. Pathology on both patients later demonstrated severe PVD. These findings suggest that HP (129)Xe MRI may be useful in the diagnosis of PVD and monitoring response to therapy. Further studies are required to determine its sensitivity and specificity in these settings.

Keywords: magnetic resonance imaging; pulmonary hypertension; pulmonary vascular disease; xenon.

Figures

Figure 1

129Xe hyperpolarized magnetic resonance imaging (MRI) and spectroscopy in a healthy individual. A, High-resolution 129Xe ventilation MRI with normal homogeneous distribution. B, Gas spectroscopy demonstrating xenon signals in red blood cells (RBCs), barrier tissue, and gas-phase xenon in the airspaces. C, Representative slices from single-breath 3-D images of Xe in gas, barrier, and RBCs, depicting homogeneous distributions.

Figure 2

Imaging and pathology from case 1. A, Representative axial computed tomography image demonstrating no significant abnormalities. B, 129Xe magnetic resonance imaging of ventilation demonstrating no significant abnormalities. C, 129Xe spectroscopy showing a severe decrease in xenon signal in red blood cells (RBCs) relative to barrier tissue (left) and representative single-breath gas exchange images showing homogeneous gas and barrier signal while 129Xe transfer to RBCs contains severe focal abnormalities (right). D, Pathology demonstrating pulmonary venoocclusive disease.

Figure 3

Imaging and pathology from case 2. A, Representative axial computed tomography image of the lungs demonstrating no significant abnormalities near the bases. Mild upper lobe emphysema was noted on other images (not shown). B, 129Xe magnetic resonance imaging of ventilation demonstrating mild peripheral ventilation defects and mild upper lobe emphysema. C, 129Xe spectroscopy exhibiting a moderate decrease in xenon signal in red blood cells (RBCs) relative to barrier tissue (left) and single-breath gas exchange images demonstrating homogeneous gas and barrier signal while xenon uptake in RBCs contained severe focal abnormalities (right). D, Pathology demonstrating pulmonary hypertensive arteriopathy.

Figure 4

Differences in ventilation imaging between subjects with pulmonary vascular disease (PVD; A) and idiopathic pulmonary fibrosis (IPF; B). Subjects with PVD appear to have fairly normal ventilation with relatively high lung compliance (blue), while those with IPF appear to lose high-intensity signal (loss of blue signal), consistent with a loss of lung compliance.