# Lung Density Measurement in Fontan Patients Using Zero Echo Time Sequences

## TL;DR

This study explores using MRI to measure lung density in patients who have undergone a Fontan procedure, linking lung density to heart and lung health indicators.

## Contribution

The study introduces lung density measurement via zero echo time MRI as a potential diagnostic tool for Fontan patients.

## Key findings

- Patients with higher lung-to-background ratio (LBR) showed increased extracellular volume and decreased TIMP-1 and sST-2 levels.
- Elevated LBR was associated with a history of higher pulmonary arterial pressure and collateral embolization.
- LBR did not correlate with most cardiovascular or pulmonary parameters, suggesting lung density is a unique indicator.

## Abstract

Pulmonary complications are known to occur in patients after Fontan palliation. Cardiac MRI is performed in the follow-up of Fontan patients to assess single ventricular function, hemodynamics and potential collateral flow. To date, pulmonary function tests have been used to detect functional lung impairment, but lung MRI has not been integrated into imaging follow-up. In this study, we measured lung-to-background ratio (LBR) on zero echo time (ZTE) MRI sequences in 32 children with Fontan palliation. Patients were divided into 2 groups: LBR > 1.5 and < 1.5 and assessed for associations between LBR and ventricular function, fibrosis, hemodynamics as well as biomarkers, spirometry and previous catheter results. We observed significantly increased extracellular volume (ECV) and decreased tissue inhibitor of metalloproteinase 1 (TIMP-1), soluble suppression of tumorigenicity 2 (sST-2) and a trend towards decreased growth differentiation factor 15 (GDF-15) as well as decreased albumin and prothrombin time values in patients with elevated LBR, whereas the other cardiovascular and pulmonary parameters did not differ significantly. Moreover, patients with LBR > 1.5 had a history of increased pulmonary arterial pressure prior to the Fontan and Glenn procedures and interventional veno-venous collateral embolization. Monitoring lung density with ZTE MRI sequences may be helpful in the diagnostic workup to assess the outcome of patients after Fontan procedure.