Assessment of lung density in pediatric patients using three-dimensional ultrashort echo-time and four-dimensional zero echo-time sequences

Konstantinos G. Zeimpekis,Julia Geiger,Christian J. Kellenberger

doi:10.1007/s11604-022-01258-1

Konstantinos G. Zeimpekis, Julia Geiger + Show 1 more

Open Access

https://doi.org/10.1007/s11604-022-01258-1

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Abstract

PurposeLung magnetic resonance imaging (MRI) using conventional sequences is limited due to strong signal loss by susceptibility effects of aerated lung. Our aim is to assess lung signal intensity in children on ultrashort echo-time (UTE) and zero echo-time (ZTE) sequences. We hypothesize that lung signal intensity can be correlated to lung physical density.Materials and methodsLung MRI was performed in 17 children with morphologically normal lungs (median age: 4.7 years, range 15 days to 17 years). Both lungs were manually segmented in UTE and ZTE images and the average signal intensities were extracted. Lung-to-background signal ratios (LBR) were compared for both sequences and between both patient groups using non-parametric tests and correlation analysis. Anatomical region-of-interest (ROI) analysis was performed for the normal cohort for assessment of the anteroposterior lung gradient.ResultsThere was no significant difference between LBR of normal lungs using UTE and ZTE (p < 0.05). Both sequences revealed a LBR age-dependency with a high negative correlation for UTE (Rs = – 0.77; range 2.98–1.41) and ZTE (Rs = – 0.82; range 2.66–1.38)). Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were age-dependent for both sequences. SNR was higher for children up to 2 years old with 3D UTE Cones while for the rest it was higher with 4D ZTE. CNR was similar for both sequences. Posterior lung areas exhibited higher signal intensity compared to anterior ones (UTE 9.4% and ZTE 12% higher), both with high correlation coefficients (R2UTE = 0.94, R2ZTE = 0.97).ConclusionThe ZTE sequence can measure signal intensity similarly to UTE in pediatric patients. Both sequences reveal an age- and gravity-dependency of LBR.

Highlights

Magnetic resonance imaging (MRI) for assessment of lung parenchyma used to be challenging and its clinical application in children was limited in the past
MRI provides an important advantage in avoiding radiation exposure in children, who are the most radiosensitive [9], establishing it as safer compared to Computed tomography (CT) for follow-up scans of pediatric patients [10]
This study showed that ZTE provided higher SNR for the lung parenchyma compared to UTE

Summary

Introduction

Magnetic resonance imaging (MRI) for assessment of lung parenchyma used to be challenging and its clinical application in children was limited in the past. MRI has been becoming more popular in pediatric exams of lung pathologies and airways in recent years thanks to technical advances and emergence of new sequences [1–8]. Ultrashort echo-time and zero echo-time sequences are designed to capture the rapid decaying T2* signal of tissues like the lung or bone. Both sequences have been implemented for lung morphology and pathology [11–16], and ultrashort echo-time sequences have been recently used for COVID-19 patients [17–19]

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