3D Single-Breath Chemical Shift Imaging Hyperpolarized Xe-129 MRI of Healthy, CF, IPF, and COPD Subjects

Abstract

3D Single-breath Chemical Shift Imaging (3D-SBCSI) is a hybrid MR-spectroscopic imaging modality that uses hyperpolarized xenon-129 gas (Xe-129) to differentiate lung diseases by probing functional characteristics. This study tests the efficacy of 3D-SBCSI in differentiating physiology among pulmonary diseases. A total of 45 subjects-16 healthy, 11 idiopathic pulmonary fibrosis (IPF), 13 cystic fibrosis (CF), and 5 chronic obstructive pulmonary disease (COPD)-were given 1/3 forced vital capacity (FVC) of hyperpolarized Xe-129, inhaled for a ~7 s MRI acquisition. Proton, Xe-129 ventilation, and 3D-SBCSI images were acquired with separate breath-holds using a radiofrequency chest coil tuned to Xe-129. The Xe-129 spectrum was analyzed in each lung voxel for ratios of spectroscopic peaks, chemical shifts, and T2* relaxation. CF and COPD subjects had significantly more ventilation defects than IPF and healthy subjects, which correlated with FEV1 predicted (R = -0.74). FEV1 predicted correlated well with RBC/Gas ratio (R = 0.67). COPD and IPF had significantly higher Tissue/RBC ratios than other subjects, longer RBC T2* relaxation times, and greater RBC chemical shifts. CF subjects had more ventilation defects than healthy subjects, elevated Tissue/RBC ratio, shorter Tissue T2* relaxation, and greater RBC chemical shift. 3D-SBCSI may be helpful in the detection and characterization of pulmonary disease, following treatment efficacy, and predicting disease outcomes.

Keywords: COPD; MRI; cystic fibrosis; hyperpolarized xenon-129; idiopathic pulmonary fibrosis.

Figure 1

Ventilation images from a healthy subject and each disease type. Bright, homogeneous areas show that the lungs are ventilating normally.

Figure 2

Ventilation images overlaid on proton images in sample healthy, IPF, CF, and COPD subjects. Each row shows five lung slices from anterior (left) to posterior (right). Green areas indicate regions of normal ventilation and hyperventilation. Orange areas indicate regions of hypoventilation. Red areas indicate regions of no ventilation.

Figure 3

Tissue/RBC ratio maps (top) and boxplots (bottom) for each disease type. (p < 0.001 = ***, ⁺ outlier).

Figure 4

RBC/Gas ratio maps (top) and boxplots (bottom) for each disease type. (p < 0.001 = ***, p < 0.01 = **, p < 0.5 = *).

Figure 5

Tissue/Gas ratio maps (top) and boxplots (bottom) for each disease type. (p < 0.001 = ***, p < 0.01 = **, p < 0.5 = *, ⁺ outlier).

Figure 6

Tissue T2* maps (top) and boxplots (bottom) for each disease type. (p < 0.01 = **, p < 0.5 = *, ⁺ outlier).

Figure 7

RBC T2* maps (top) and boxplots (bottom) for each disease type. (p < 0.01 = **, p < 0.5 = *).

Figure 8

Tissue chemical shift maps (top) and boxplots (bottom) for each disease type. The color bar corresponds to the location of the geometric center of the tissue peak. Results are not significantly different. (⁺ outlier).

Figure 9

RBC chemical shift maps (top) and boxplots (bottom) for each disease type. The color bar corresponds to the location of the geometric center of the RBC peak. (p < 0.001 = ***, p < 0.01 = **).