Normalized T1 Magnetic Resonance Imaging for Assessment of Regional Lung Function in Adult Cystic Fibrosis Patients - A Cross-Sectional Study

Elliott C Dasenbrook,Shannon Donnola,Vikas Gulani,Chris A Flask,Lan Lu,Michael W Konstan,Peter M Jakob,David E Weaver

doi:10.1371/journal.pone.0073286

Abstract

BackgroundCystic fibrosis (CF) patients would benefit from a safe and effective tool to detect early-stage, regional lung disease to allow for early intervention. Magnetic Resonance Imaging (MRI) is a safe, non-invasive procedure capable of providing quantitative assessments of disease without ionizing radiation. We developed a rapid normalized T1 MRI technique to detect regional lung disease in early-stage CF patients.Materials and MethodsConventional multislice, pulmonary T1 relaxation time maps were obtained for 10 adult CF patients with normal spirometry and 5 healthy non-CF control subjects using a rapid Look-Locker MRI acquisition (5 seconds/imaging slice). Each lung absolute T1 map was separated into six regions of interest (ROI) by manually selecting upper, central, and lower lung regions in the left and right lungs. In order to reduce the effects of subject-to-subject variation, normalized T1 maps were calculated by dividing each pixel in the absolute T1 maps by the mean T1 time in the central lung region. The primary outcome was the differences in mean normalized T1 values in the upper lung regions between CF patients with normal spirometry and healthy volunteers.ResultsNormalized T1 (nT1) maps showed visibly reduced subject-to-subject variation in comparison to conventional absolute T1 maps for healthy volunteers. An ROI analysis showed that the variation in the nT1 values in all regions was ≤2% of the mean. The primary outcome, the mean (SD) of the normalized T1 values in the upper right lung regions, was significantly lower in the CF subjects [.914 (.037)] compared to the upper right lung regions of the healthy subjects [.983 (.003)] [difference of .069 (95% confidence interval .032−.105); p = .001). Similar results were seen in the upper left lung region.ConclusionRapid normalized T1 MRI relaxometry obtained in 5 seconds/imaging slice may be used to detect regional early-stage lung disease in CF patients.

Highlights

Cystic Fibrosis (CF) is the most common life-shortening autosomal recessive disorder in persons of European ancestry[1]
The primary outcome, the mean (SD) of the normalized T1 values in the upper right lung regions, was significantly lower in the Cystic fibrosis (CF) subjects [.914 (.037)] compared to the upper right lung regions of the healthy subjects [.983 (.003)] [difference of .069 (95% confidence interval .0322.105); p = .001)
CF patients ages ranged from 18–49 years and the mean [standard deviation (SD)] FEV1 was 93% predicted (14.5) and ranged from 73% to 123% predicted

Summary

Introduction

Cystic Fibrosis (CF) is the most common life-shortening autosomal recessive disorder in persons of European ancestry[1]. Adolescent and adult CF patients with early-stage lung disease are more common as evidenced by 50% of CF patients in the United States aged $18 years having a forced expiratory volume in one second (FEV1) value greater than 80% of predicted for a healthy population[3]. Clinical tools such as spirometry, bronchoscopy, and chest imaging are typically used to detect CF lung disease. We developed a rapid normalized T1 MRI technique to detect regional lung disease in early-stage CF patients

Methods

Results

Conclusion