Back to the future: sagittal CT in the evaluation of COPD.

OBJECTIVES: To identify features of obstructive airway disease on sagittal reconstruction, compare the accuracy of findings to traditional imaging characteristics of COPD, and determine the fraction of additional cases identified using new characteristics. METHODS: The study was approved by the centre's Institutional Review Board and is HIPAA compliant. Two hundred sixteen patients with HRCT and spirometry within a 3-month window were included. Four radiologists evaluated each HRCT for traditional characteristics of COPD and new quantitative and qualitative features of obstruction on axial and sagittal reconstructions. Imaging characteristics were assessed for correlation with the spirometric diagnosis of obstructive airway disease. RESULTS: Quantitative and qualitative findings on sagittal reconstruction are highly specific for COPD (specificity >90 %). Features of hyperinflation on sagittal reconstruction are more accurate predictors of obstruction than traditional axial measures, with greater interobserver reliability (hyperinflation left hemidiaphragm: accuracy: 70.08 % ± 2.49 %; kappa: 0.511 versus traditional measures: accuracy: 62.00 % ± 5.38 %; kappa: 0.407). Sagittal reconstruction identified 27-70 % more patients with COPD than traditional axial findings (p < 0.05). CONCLUSIONS: Analysis of sagittal reconstruction enables greater accuracy and specificity in the diagnosis of obstructive airway disease compared to traditional measures on axial imaging. Use of sagittal reconstructions can help identify up to 70 % more patients with COPD than traditional imaging findings alone. KEY POINTS: • HRCT sagittal reconstruction is useful in the evaluation of obstructive lung disease. • Findings on sagittal reconstructions allow physicians to more accurately diagnose COPD. • Routine use of sagittal reconstructions increases the sensitivity for diagnosing COPD.