Correlation of helical and incremental high-resolution thin-section computed tomographic and histomorphometric quantitative evaluation of an acute inflammatory response of lungs in dogs

OBJECTIVE: To compare quantitative densitometric computed tomography (CT), morphometric, and histologic data of normal lungs in dogs with similar parameters obtained after induction of an acute inflammatory response and determine whether CT densitometry correlated with histopathologic changes. ANIMALS: 6 healthy adult dogs. PROCEDURE: After initial CT, 1 mL of 0.1 M hydrochloric acid (HCI) and 3 mL of autologous blood were instilled into the right middle (RM) and caudal segment of the left cranial (LCCd) lung lobes, respectively. Immediately and 24 hours after instillation, CT was repeated. At 24 hours, dogs were euthanatized and lungs were fixed and sampled for morphometric and histologic evaluation. The CT data were compared with lung morphology and morphometry by use of unpaired t tests. Comparison with lungs from control dogs was performed using Spearman rank correlation coefficients. RESULT: Mean Hounsfield units (HU) from control and baseline HU from experimental dogs were identical. Immediately after instillation of HCI or blood, there was increased attenuation in both lobes. Autologous blood initially induced severe changes that almost completely resolved at 24 hours; HCI induced severe changes at 24 hours. Significant increases in percentage of parenchymal airspace and alveolar diameter resulted in decreased surface area-to-volume ratio in lobes receiving HCl. Histologic scores were significantly higher in the RM lobe, compared with controls. CONCLUSIONS AND CLINICAL RELEVANCE: Computed tomography attenuation correlated well with histomorphometry and histologic findings in this model. Lung lesions after autologous blood were transient and of limited severity. Lesions induced by HCl were severe; alterations in morphometric and histologic parameters were reflected in CT attenuation measurements.