Deriving Regionally Specific Biomarkers of Emphysema and Small Airways Disease Using Variable Threshold Parametric Response Mapping on Volumetric Lung CT Images
| Autor: | R. Baron, Rahim R. Rizi, L. Loza, Hooman Hamedani, Stephen Kadlecek, Yi Xin, F. Amzajerdian, Ian Duncan |
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| Rok vydání: | 2022 |
| Předmět: |
Male
Supine position computer.software_genre Article Rats Sprague-Dawley Voxel Vertical gradient Animals Medicine Radiology Nuclear Medicine and imaging Lung Lung function Parametric statistics Emphysema business.industry Cone-Beam Computed Tomography Rats Lung density Small airways disease medicine.anatomical_structure Tomography X-Ray Computed business Nuclear medicine computer Biomarkers |
| Zdroj: | Acad Radiol |
| ISSN: | 1076-6332 |
| Popis: | Purpose This study aims to develop and validate a parametric response mapping (PRM) methodology to accurately identify diseased regions of the lung by using variable thresholds to account for alterations in regional lung function between the gravitationally-independent (anterior) and gravitationally-dependent (posterior) lung in CT images acquired in the supine position. Methods 34 male Sprague-Dawley rats (260-540 g) were imaged, 4 of which received elastase injection (100 units/kg) as a model for emphysema (EMPH). Gated volumetric CT was performed at end-inspiration (EI) and end-expiration (EE) on separate groups of free-breathing (n = 20) and ventilated (n = 10) rats in the supine position. To derive variable thresholds for the new PRM methodology, voxels were first grouped into 100 bins based on the fractional distance along the anterior-to-posterior direction. Lower limits of normal (LLN) for x-ray attenuation in each bin were set by determining the smallest region that enclosed 98% of voxels from healthy, ventilated animals. Results When utilizing fixed thresholds in the conventional PRM methodology, a distinct posterior-anterior gradient was seen, in which nearly the entire posterior region of the lung was identified as HEALTHY, while the anterior lung was labeled as significantly less so (t(29) = -3.27, p = 0.003). In both cohorts, %SAD progressively increased from posterior to anterior, while %HEALTHY lung decreased in the same direction. After applying our PRM methodology with variable thresholds to the same rat images, the posterior-anterior trend in %SAD quantification was removed from all rats and the significant increase of diseased lung in the anterior was removed. Conclusions The PRM methodology using variable thresholds provides regionally specific markers of %SAD and %EMPH by correcting for alterations in regional lung function associated with the naturally occurring vertical gradient of dependent vs. non-dependent lung density and compliance. |
| Databáze: | OpenAIRE |
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