title: Lung imaging in rodents using dual energy micro-CT.
abstract: Dual energy CT imaging is expected to play a major role in the diagnostic arena as it provides material decomposition on an elemental basis. The purpose of this work is to investigate the use of dual energy micro-CT for the estimation of vascular, tissue, and air fractions in rodent lungs using a post-reconstruction three-material decomposition method. We have tested our method using both simulations and experimental work. Using simulations, we have estimated the accuracy limits of the decomposition for realistic micro-CT noise levels. Next, we performed experiments involving ex vivo lung imaging in which intact lungs were carefully removed from the thorax, were injected with an iodine-based contrast agent and inflated with air at different volume levels. Finally, we performed in vivo imaging studies in (n=5) C57BL/6 mice using fast prospective respiratory gating in end-inspiration and end-expiration for three different levels of positive end-expiratory pressure (PEEP). Prior to imaging, mice were injected with a liposomal blood pool contrast agent. The mean accuracy values were for Air (95.5%), Blood (96%), and Tissue (92.4%). The absolute accuracy in determining all fraction materials was 94.6%. The minimum difference that we could detect in material fractions was 15%. As expected, an increase in PEEP levels for the living mouse resulted in statistically significant increases in air fractions at end-expiration, but no significant changes in end-inspiration. Our method has applicability in preclinical pulmonary studies where various physiological changes can occur as a result of genetic changes, lung disease, or drug effects.
authors.affiliation: Center for In Vivo Microscopy, Department of Radiology, Tsinghua University, Beijing, China.
authors.forename: C T
authors.initials: CT
authors.lastname: Badea
authors.forename: X
authors.initials: X
authors.lastname: Guo
authors.forename: D
authors.initials: D
authors.lastname: Clark
authors.forename: S M
authors.initials: SM
authors.lastname: Johnston
authors.forename: C
authors.initials: C
authors.lastname: Marshall
authors.forename: C
authors.initials: C
authors.lastname: Piantadosi
keywords: Micro-CT; dual energy; lung; small animal imaging
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