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J. M. Reinhardt, S. A. Raab, N. D. D'Souza, and E. A. Hoffman. Intra-thoracic airway measurement: Ex vivo validation. In E. A. Hoffman, ed., Proc. SPIE Conf. Medical Imaging, vol. 3033, pp. 69-80, Newport Beach, CA, 1997.

Abstract: High-resolution X-ray CT (HRCT) provides detailed images of the lungs and bronchial tree. HRCT-based imaging and quantitation of peripheral bronchial airway geometry provides a valuable tool for assessing regional airway physiology. Such measurements have been used to address physiological questions related to the mechanics of airway collapse in sleep apnea, the measurement of airway response to broncho-constriction agents, and to evaluate and track the progression of disease affecting the airways, such as asthma and cystic fibrosis. Significant attention has been paid to the measurement of extra- and intra-thoracic airways in two-dimensional sections from volumetric X-ray CT. A variety of manual and semi-automatic techniques have been proposed for airway geometry measurement, including the use of standardized display window and level settings for caliper measurements, methods based on manual or semi-automatic border tracing, and more objective, quantitative approaches such as the use of the ?half-max? criteria. A recently proposed measurement technique uses a model-based deconvolution to estimate the location of the inner and outer airway walls. Validation using a plexiglass phantom indicates that the model-based method is more accurate than the half-max approach for thin-walled structures. In vivo validation of these airway measurement techniques is difficult because of the problems in identifying a reliable measurement ?gold standard.? In this paper we report on ex vivo validation of the half-max and model-based methods using an excised pig lung. The lung is sliced into thin sections of tissue and scanned using an electron beam CT scanner. Airways of interest are measured from the CT images, and also measured with using a microscope and micrometer to obtain a measurement gold standard. The results show no significant difference between the model-based measurements and the gold standard (p $<$ 0.01); while the half-max estimates exhibited a measurement bias and were significantly different than the gold standard (p $<$ 0.01).

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Keywords: airways measurement

Other publications by: J. M. Reinhardt, S. A. Raab, N. D. D'Souza, E. A. Hoffman

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