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Characterization of R2and tissue density in the human lung: Application to neonatal imaging in the intensive care unit
Journal article   Peer reviewed

Characterization of R2and tissue density in the human lung: Application to neonatal imaging in the intensive care unit

Andrew D. Hahn, Annelise Malkus, Jeffery Kammerman, Nara Higano, Laura Walkup, Jason Woods and Sean B. Fain
Magnetic resonance in medicine, Vol.84(2), pp.920-927
08/01/2020
DOI: 10.1002/mrm.28137
PMCID: PMC7180096
PMID: 31855294
url
https://www.ncbi.nlm.nih.gov/pmc/articles/7180096View
Open Access

Abstract

Purpose Novel demonstration of R2* and tissue density estimation in infant lungs using 3D ultrashort echo time MRI. Differences between adult and neonates with no clinical indication of lung pathology is explored, as well as relationships between parameter estimates and gravitationally dependent position and lung inflation state. This provides a tool for probing physiologic processes that may be relevant to pulmonary disease and progression in newborns. Methods R2* and tissue density were estimated in a phantom consisting of standards allowing for ground truth comparisons and in human subjects (N = 5 infants, N = 4 adults, no clinical indication of lung dysfunction) using a 3D radial multiecho ultrashort echo time MRI sequence. Whole lung averages were compared between infants and adults. Dependence of the metrics on anterior-posterior position as well as between end-tidal inspiration and expiration were explored, in addition to the general relationship between R2* and tissue density. Results Estimates in the phantom did not differ significantly from ground truth. Neonates had significantly lower mean R2* (P = .006) and higher mean tissue density (P = 1.5e-5) than adults. Tissue density and R2* were both significantly dependent on anterior-posterior position and lung inflation state (P < .005). An overall inverse relationship was found between R2* and tissue density, which was similar in both neonates and adults. Conclusion Estimation of tissue density and R2* in free breathing, nonsedated, neonatal patients is feasible using multiecho ultrashort echo time MRI. R2* was no different between infants and adults when matched for tissue density, although density of lung parenchyma was, on average, lower in adults than neonates.
Life Sciences & Biomedicine Radiology, Nuclear Medicine & Medical Imaging Science & Technology

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