肺部CT图像的自动评估：基于形态学的概念。

Automated CT image evaluation of the lung: a morphology-based concept.

作者信息

Blechschmidt R A, Werthschützky R, Lörcher U

机构信息

University of Technology, Department of Electrical Engineering and Information Technology, Darmstadt, Germany.

出版信息

IEEE Trans Med Imaging. 2001 May;20(5):434-42. doi: 10.1109/42.925296.

DOI:10.1109/42.925296

PMID:11403202

Abstract

UNLABELLED

Computed tomography (CT) provides the most reliable method to detect emphysema in vivo. Commonly used methods only calculate the area of low attenuation [pixel index (PI)], while a radiologist considers the bullous morphology of emphysema. The PI is a good, well-known measure of emphysema. But it is not able to detect emphysema in cases in which emphysema and fibrosis occur at the same time. This is because fibrosis leads to a low number of low-attenuation pixels, while emphysema leads to a high number of pixels. The PI takes the average of both and, consequently, may present a result within the normal range.

METHOD

The main focus of this paper is to present a new algorithm of thoracic CT image evaluation based on pulmonary morphology of emphysema. The PI is extended, in that it is enabled to differentiate between small, medium, and large bullae (continuous low-attenuation areas). It is not a texture-based algorithm. The bullae are sorted by size into four size classes: class 1 being within the typical size of lung parenchyma; classes 2-4 presenting small, medium, and large bullae. It is calculated how much area the different classes take up of all low-attenuation pixels. The bullae index (BI) is derived from the percentage of areas covered, respectively, by small, medium, and large bullae. From the relation of the area of bullae belonging to class 4, to that of those belonging to class 2, a measure of the emphysema type (ET)is calculated. It classifies the lung by the type of emphysema in bullous emphysema or small-sized, diffuse emphysema, respectively.

RESULTS

The BI is as reliable as the PI. In cases in which the PI indicates normal values while in fact emphysema is coexisting with fibrosis, the BI, nevertheless, detects the destruction caused by the emphysema. The BI combined with the ET reflects the visual assessment of the radiological expert.

CONCLUSION

The BI is an objective and reliable index in order to quantify emphysematous destruction, hence, avoiding interobserver variance. This is particularly interesting for follow-up. The classification of the ET is a helpful and unique approach to achieving an exact diagnosis of emphysema.

摘要

未标注

计算机断层扫描（CT）是检测体内肺气肿最可靠的方法。常用方法仅计算低衰减区域面积[像素指数（PI）]，而放射科医生会考虑肺气肿的肺大疱形态。PI是一种常用且熟知的肺气肿测量指标。但在肺气肿与纤维化同时出现的情况下，它无法检测出肺气肿。这是因为纤维化导致低衰减像素数量少，而肺气肿导致像素数量多。PI取两者的平均值，因此可能呈现出正常范围内的结果。

方法

本文的主要重点是提出一种基于肺气肿肺部形态的胸部CT图像评估新算法。对PI进行了扩展，使其能够区分小、中、大肺大疱（连续低衰减区域）。这不是一种基于纹理的算法。肺大疱按大小分为四个尺寸类别：1类在肺实质的典型大小范围内；2 - 4类分别表示小、中、大肺大疱。计算不同类别在所有低衰减像素中所占的面积。肺大疱指数（BI）由小、中、大肺大疱分别覆盖的面积百分比得出。根据4类肺大疱面积与2类肺大疱面积的关系，计算出肺气肿类型（ET）的一个指标。它分别根据肺大疱性肺气肿或小灶性、弥漫性肺气肿的类型对肺进行分类。