Application Of Automatic Airway Measurement Based On CT Images To Quantitative Diagnosis Of COPD

Chronic Obstructive Pulmonary Disease (COPD) is a major cause of morbidity and mortality worldwide. It is easily to led to misdiagnosis and missed-diagnosis of COPD by the pulmonary function test. There is still lack of sensitive and specific criteria to evaluate the COPD at its earlier stage now. With the development of CT technology, quantitative airway measurement on CT images is becoming the research focus of the diagnosis of COPD with small airway diseases. Due to the influence of blurring introduced during CT imaging procedure and the limitations of measurement methods, accurate airway measurement has become a crucial problem to use the CT images to diagnose the COPD with small airway diseases.The airway phantom, which was made from poly-acryl tubes with different sizes embedded in foam, was scanned with Siemens64-multi-detector row CT scanner. The scan data obtained with different FOV was reconstructed into CT images with different reconstruction kernels. The CT images of the airway phantom were measured by full width at half maximum (FWHM), zero crossing (ZC), Model-Based (M-B) and phase congruency (PC), and the measurement errors were compared. The results of phantom experiment show that, for the tubes with the thickness of about1-2mm, the accuracy of FWHM and ZC is influenced most by reconstruction kernels, and the error range reached the minimum at B50f; the accuracy of M-B is also influenced by reconstruction kernels, but its error range is small; PC is insensitive to reconstruction kernels, but it obviously overestimates the thickness of small tube.Thoracic CT images of diagnosed COPD patients with small airway diseases were collected and the airways from3rd to5th generation were measured with the4methods described above. The airway parameters were analyzed to find the difference between COPD patients with different stage. The results show that, on the thoracic CT images of COPD patients, the ratio of wall thickness to outer diameter (TD%) and the ratio of airway wall area to outer lumen area (WA%) of the3rd and 4th generation of airways obtained by M-B method are expected to be the indication for COPD quantitative diagnosis with enlarged sample size.