Hyperpolarised xenon-129 diffusion-weighted magnetic resonance imaging for assessing lung microstructure in...

Hyperpolarised 129-xenon (¹²⁹Xe) magnetic resonance imaging (MRI) shows promise in monitoring the progression of idiopathic pulmonary fibrosis (IPF) due to the lack of ionising radiation and the ability to quantify functional impairment. Diffusion-weighted (DW)-MRI with hyperpolarised gases can provide information about lung microstructure. The aims were to compare ¹²⁹Xe DW-MRI measurements with pulmonary function tests (PFTs), and to assess whether they can detect early signs of disease progression in patients with newly diagnosed IPF.

This is a prospective, single-centre, observational imaging study of patients presenting with IPF to Northern General Hospital (Sheffield, UK). Hyperpolarised ¹²⁹Xe DW-MRI was performed at 1.5 T on a whole-body General Electric HDx scanner and PFTs were performed on the same day as the MRI scan.

There was an increase in global ¹²⁹Xe apparent diffusion coefficient (ADC) between the baseline and 12-month visits (mean 0.043 cm²·s^-1, 95% CI 0.040-0.047 cm²·s^-1 versus mean 0.045 cm²·s^-1, 95% CI 0.040-0.049 cm²·s^-1; p=0.044; n=20), with no significant change in PFTs over the same time period. There was also an increase in ¹²⁹Xe ADC in the lower zone (p=0.027), and an increase in ¹²⁹Xe mean acinar dimension in the lower zone (p=0.033) between the baseline and 12-month visits. ¹²⁹Xe DW-MRI measurements correlated strongly with diffusing capacity of the lung for carbon monoxide (% predicted), transfer coefficient of the lung for carbon monoxide (K_CO) and K_CO (% predicted).

¹²⁹Xe DW-MRI measurements appear to be sensitive to early changes of microstructural disease that are consistent with progression in IPF at 12 months. As new drug treatments are developed, the ability to quantify subtle changes using ¹²⁹Xe DW-MRI could be particularly valuable.