肺炎胸部X光表徵評估之電腦輔助診斷系統

Abstract

胸部Ｘ光因能顯現肺部表徵，故在肺炎的臨床診斷上有很重要的地位。肺炎在早期通常只有輕微的肺部Ｘ光表徵，容易被肉眼所忽略而影響診療。在這項研究中，我們發展了一套肺炎胸部Ｘ光之電腦輔助診斷系統。這套電腦輔助診斷系統由兩個部分所構成。其中一部分利用邊界偵測及二維小波轉換等技術以擷取肺炎胸部Ｘ光表徵。另一部分則利用二維非線性影像扭轉技術以減少Ｘ光影像間因拍攝參數及病患姿勢不同所造成空間結構之差異。將同一病患不同時間所拍攝之胸部Ｘ光影像對齊可應用在長期觀察之上。將不同病患的胸部Ｘ光影像對齊則可提高病患間相互比較之可能性。跟據我們的實驗結果，所發表的電腦輔助診斷系統可量化浸潤現象。且所擷取之肺炎表徵隨病情演進之變化和臨床上插管，拔管之時間點能夠互相印證。

Chest X-ray (CXR) is important for clinical diagnosis of pneumonia due to its ability to reveal pulmonary manifestation. In the early stage of pneumonia, pneumonic findings are subtle on plain films and can easily escape detection by visual inspection. In this work, we develop a computer-aided diagnosis (CAD) system in chest radiography for pneumonia. There are two major components in this CAD system. The first component comprises image processing techniques, such as edge detection and 2-D Haar wavelet transform, for the feature extraction of pneumonic manifestations in CXR images. The other one consists of 2-D nonlinear image warping techniques and can reduce the structural displacements in CXR images due to the variations of acquisition conditions and postures across examinations. Registering CXR images of the same subject can be useful for longitudinal study. Moreover, registering CXR images across subjects provides the possibility of inter-subject comparison. According to our experiments, the proposed CAD system can extract the infiltration in the lung field of CXR images. Furthermore, the progress of the extracted features is coherent to the diagnostic decisions of the timing of intubation and extubation for SARS patients.