Oxygen-sensitive 3He-MRI in bronchiolitis obliterans after lung transplantation

Abstract

Oxygen-sensitive 3 He-MRI was studied for the detection of differences in intrapulmonary oxygen partial pressure (pO 2 ) between patients with normal lung transplants and those with bronchiolitis obliterans syndrome (BOS). Using software developed in-house, oxygen-sensitive 3 He-MRI datasets from patients with normal lung grafts (n=8) and with BOS (n=6) were evaluated quantitatively. Datasets were acqiured on a 1.5-T system using a spoiled gradient echo pulse sequence. Underlying diseases were pulmonary emphysema (n=10 datasets) and fibrosis (n=4). BOS status was verified by pulmonary function tests. Additionally, 3 He-MRI was assessed blindedly for ventilation defects. Median intrapulmonary pO 2 in patients with normal lung grafts was 146 mbar compared with 108 mbar in patients with BOS. Homogeneity of pO2 distribution was greater in normal grafts (standard deviation pO2 34 versus 43 mbar). Median oxygen decrease rate during breath hold was higher in unaffected patients (−1.75 mbar/s versus −0.38 mbar/s). Normal grafts showed fewer ventilation defects (5% versus 28%, medians). Oxygen-sensitive 3 He-MRI appears capable of demonstrating differences of intrapulmonary pO2 between normal lung grafts and grafts affected by BOS. Oxygen-sensitive 3 He-MRI may add helpful regional information to other diagnostic techniques for the assessment and followup of lung transplant recipients.

Imaging of lung function using hyperpolarized helium‐3 magnetic resonance imaging: Review of current and emerging translational methods and applications

“…Recent work has allowed measurement within a single breath-hold (85,87). The technique has potential application in pulmonary embolism (88) and in bronchiolitis obliterans after lung transplant (89)…”

3He pO2 mapping is limited by delayed‐ventilation and diffusion in chronic obstructive pulmonary disease

“…For free 3 He diffusion in air D ¼ 0.86 cm 2 /s (7), whereas smaller apparent diffusion coefficients (ADCs) are characteristic of longer diffusion times in healthy acinar tissue when measured with longitudinal diffusion weighted magnetization pulse sequences (8-11). Similarly, any other change in signal decay, which is not related to oxygen concentration or RF depolarization, such as a delayed in-flow of gas into the region of interest (ROI), could cause errors in the pO 2 values calculated with the technique.3 He pO 2 mapping has been used to image patients with bronchiolitis obliterans (12) and lung transplant (12,13), and several studies have performed pO 2 mapping in patients with chronic obstructive pulmonary disease (COPD) (13)(14)(15)(16)(17). COPD is characterized by abnormalities of air-flow and elevation in regional gas ADC related to emphysema in the alveolar spaces (18).…”

“…3 He pO 2 mapping has been used to image patients with bronchiolitis obliterans (12) and lung transplant (12,13), and several studies have performed pO 2 mapping in patients with chronic obstructive pulmonary disease (COPD) (13)(14)(15)(16)(17). COPD is characterized by abnormalities of air-flow and elevation in regional gas ADC related to emphysema in the alveolar spaces (18).…”

Chronic Allograft Rejection: Epidemiology, Diagnosis, Pathogenesis, and Treatment

“…Other potential measures include exhaled breath condensate, 141 methacholine challenge, 142 induced sputum, 143 and hyperpolarized 3 He magnetic resonance imaging. 144 However, the predictive value of these techniques in prospective longitudinal studies remains to be determined.…”