Room: AAPM ePoster Library
Purpose: airway dimensions with luminal diameter less than 2mm are important biomarker for the airway obstruction disease such as asthma and chronic obstructive pulmonary disease (COPD). This study validates an integrated intensity-based (IIB) method in small airway evaluation as compared with a standard full-width half-maximum (FWHM) method.
Methods: cylindrical polyurethane phantom with 14 silicone tubing (inner diameter: 0.3-3.4mm; wall thickness: 0.15-1.6mm) was fitted in an Anthropomorphic QRM-Thorax phantom. Images of the phantom were acquired at different tube voltages (120, 100 and 80Kv) and currents (200 and 50mA) using a 320-slice CT scanner. Images were reconstructed with filtered back projection (FPB) or an adaptive iterative algorithm (ADIR3D) with three different lung kernels. A semi-automated technique based on the integrated intensity was used to calculate the luminal diameter and wall thickness of the airway phantom. A standard FWHM method was also used for comparison purposes. The measurements were compared to the known dimensions by linear regression, t-test, root-mean-square-error(RMSE) and mean error.
Results: results of luminal diameter measurements using IIB (D_IIB) and FWHM (D_FWHM) were related to the known diameters (D_K) by D_IIB=0.95D_K-0.02 (r=0.98, RMSE=0.19mm, % error=-2.04%) and D_FWHM=0.97x_ID-0.23(r=0.96, RMSE=0.39mm, % error=-22.71%), respectively. The results of wall thickness measurement using IIB (W_IIB) and FWHM (W_FWHM) were related to the known wall thickness (W_K) by W_IIB=0.92W_K+0.06(r=0.99, RMSE=0.08mm) and W_FWHM=0.63W_K+0.64(r=0.92, RMSE=0.44mm). The mean error for the IIB and FWHM methods was calculated to be 0.01±0.01mm (2.56%) and 0.37±0.06mm (108.56%), respectively. No significant difference was found between different reconstruction algorithms. The CT dose index was in the range of 0.7-9.7mGy.
Conclusion: integrated intensity-based technique enables accurate quantification of small airway dimensions, which can potentially be used for assessment of asthma and COPD.