Using hyperpolarized 129Xe MRI to quantify regional gas transfer in idiopathic pulmonary fibrosis

Key messages What is the key question?

How can we directly and sensitively measure the regional functional impairment caused by idiopathic pulmonary fibrosis (IPF)?

What is the bottom line?

Hyperpolarised ¹²⁹Xe MRI provides non-invasive measures of pulmonary gas transfer at the alveolar capillary level that correlate robustly with diffusing capacity of the lungs for carbon monoxide, while revealing spatially resolved patterns of function that reflect a loss of gas transfer efficiency in the subpleural and basal lung in patients with IPF.

Why read on?

¹²⁹Xe MRI demonstrated three different patterns of impaired gas exchange that could represent different disease stages or phenotypes, which may aid in understanding the significant heterogeneity in disease courses often seen in IPF.

Introduction

Idiopathic pulmonary fibrosis (IPF), the most common interstitial pneumonia, is a devastating disease with a poor prognosis and estimated survival of 2-3 years after diagnosis. 1-3 Historically, treatment has been limited to lung transplantation, 1 4 but today, patients are routinely treated with antifibrotic therapy using either the tyrosine kinase inhibitor, nintedanib, or the tumour growth factor-beta inhibitor, pirfenidone. 1 5 6

However, treatment of IPF and development of new therapies continue to be hampered by the lack of reliable metrics to assess therapeutic response and disease progression. To date, the primary indicators have been forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DL_CO). 1 While DL_CO measures gas exchange, it has been difficult to standardise in multi-institutional trials. 7 Thus, FVC is used as a surrogate endpoint in most clinical trials, despite the continued lack of consensus on a threshold to define clinically significant decline, predict outcomes and validate treatment decisions. 1 8-10

The pathogenesis of IPF is thought to involve excess collagen deposition that limits the capacity of alveoli to participate in gas exchange. 4 However, the disease is heterogeneous in its distribution, and this cannot be captured using global metrics. Thus, imaging is needed to highlight and quantify disease activity regionally. To this end, high-resolution CT has become a mainstay in IPF, detecting fibrotic changes and structural abnormalities to establish the presence of a usual interstitial pneumonia (UIP) pattern without the need for surgical lung biopsies. 1 This has led to further interest in...