Automatic calculation of total lung capacity from automatically traced lung boundaries in postero-anterior and lateral digital chest radiographs

Abstract

Total lung capacity (TLC) is a very important parameter in the study of pulmonary function. In the pulmonary function laboratory, it is normally obtained using plethysmography or helium dilution techniques. Several authors have developed methods of calculating the TLC using postero-anterior (PA) and lateral chest radiographs. These methods have not been often used in clinical practice. In the present work, we have developed and automated computer-based method for the calculation of TLC, by determining the pulmonary contours from digital PA and lateral radiographs of the thorax. The automatic tracing of the pulmonary borders is carried out using: (1) a group of reference lines is determined in each radiograph; (2) a family of rectangular regions of interest (ROIs) defined, which include the pulmonary borders, and in each of them the pulmonary border is identified using edge enhancement and thresholding techniques; (3) removing outlaying points from the preliminary boundary set; and (4) the pulmonary border is corrected and completed by means of interpolation, extrapolation, and arc fitting. The TLC is calculated using a computerized form of the radiographic ellipses method of Barnhard. The pulmonary borders were automatically traced in a total of 65 normal radiographs (65 PA and 65 lateral views of the same patients). Three radiologists carried out a subjective evaluation of the automatic tracing of the pulmonary borders, with a finding of no error or only one minor error in 67.7% of the PA evaluations, and in 75.9% of the laterals. Comparing the automatically traced borders with borders traced manually by an expert radiologists, we obtained a precision of 0.990 +/- 0.001 for the PA view, and 0.985 +/- 0.002 for the lateral. The values of TLC obtained by the automatic calculation described here showed a high correlation (r = 0.98) with those obtained by applying the manual Barnhard method.

Computer aided diagnosis in chest radiography

“…With rule-based systems we mean algorithms consisting of a series of steps, each containing specific processing and, usually, certain adjustable parameters. For the segmentation of lung fields, such schemes have been proposed by Xu et al [269,270], Duryea and Boone [65], and Carrascal et al [32]. Lung segmentation by pixel classification using neural networks has been investigated by McNittGray [179,178], Hasegawa et al [103], and Tsujii et al [235].…”

“…Others deal with parts of the problem, such as detection of the outer ribcage [269], the diaphragm [270], or the costophrenic angle (where the diaphragm and the rib cage meet) [7]. A few papers are focused on lateral chest radiographs [4,32]. Table 2.1 gives an overview of papers on lung segmentation.…”

“…It was tested on 15 radiographs. Carrascal et al [32] used their rule-based segmentation of PA and lateral lung fields to estimate the TLC for 65 radiographs.…”

“…A rule-based scheme is a sequence of steps, tests and rules. Most algorithms for the segmentation of lung fields fall in this category [198,269,270,65,4,6,7,32,82,84]. Techniques employed are (local) thresholding, region growing, edge detection, ridge detection, morphologi-RB PC PA / lateral evaluation remarks Toriwaki [233,232] × PA none describes a complete analysis system Harlow [102] × PA none Chien [37,38] × PA none only right lung, result used to detect abnormalities Hasegawa [103] × PA none Pietka [198] × PA none McNitt-Gray [179,178] × PA 16 Q uses 5 anatomical classes Duryea [65] × PA 802 Q Xu [269] × PA 1000 R outer rib cage only Xu [270] × PA 300 R diaphragm edges only Armato [7] × PA 600 R costophrenic angles only Armato [4] × lateral 200 Q Armato [6] × PA 600 R Carrascal [32] × both 65 RQ Vittitoe [250] × PA 99 Q Tsujii [235] × PA 71 Q Wilson, Brown [265,28] × PA none describes a complete analysis system Vittitoe [251] × PA 115 Q uses 6 anatomical classes Van Ginneken [82,84] (Chapter 3)…”

A computer-aided diagnosis approach for emphysema recognition in chest radiography

“…Unfortunately, segmentation of lung profile in lateral views is scarcely documented in the literature [26,27]. On the other hand, lateral projection provides important diagnostic information for recognizing emphysema: expansion of the retrosternal space is appreciated only in the lateral view which also accurately describes diaphragm flattening [8].…”