Original Jpn J Radiol Technol 2000 ;
Application of Gray-level Run Length Analysis for Computerized Analysis
of Interstitial Infiltrates on Chest Radiographs

JUNJI MORISHITA, SHIGEHIKO KATSURAGAWA,1) and KUNIO DOI2)
Department of Radiological Technology, Kyoto College of Medical Technology
1)Department of Medical Engineering, Iwate Medical School
2)Kurt Rossmann Laboratories for Radiologic Image Research, Department of Radiology, University of Chicago
Received Oct. 15, 1999; Revision accepted Dec. 30, 1999; Code Nos. 530, 532

Summary
We have been developing computerized schemes using texture analysis for automated detection and characterization of interstitial infiltrates on chest radiographs. To improve the performance of the schemes, new alternative texture measures need to be developed. In this study, we applied gray-level run length analysis to digital chest x-ray images and examined its potential usefulness for the detection of interstitial infiltrates. In addition, we proposed new run length matrices, which do not depend on direction, namely, the line-component run length matrix and the area-component run length matrix. Physical texture measures were defined based on the new gray-level run length analyses, such as the total number of different line components at each gray level in the line-component run length matrix and the total number of different area components at each gray level in the area-component run length matrix. We found that gray-level nonuniformity, which shows nonuniformity of gray-level distribution in the run length matrix, was an effective measure to identify correctly most difficult normal and most difficult abnormal cases, i.e., 50% correct detection for ten difficult false-negative cases, and 18% correct detection for eleven difficult false-positive cases in the previous texture analysis. Since gray-level nonuniformity represents different properties of the interstitial infiltrate patterns compared with texture analysis based on Fourier analysis, we believe that gray-level nonuniformity provides new and alternative physical measures for the detection and characterization of interstitial infiltrates on chest radiographs. In addition, our preliminary results indicated that new texture measures which were calculated from line- or area-component run length matrices may be useful for accurate detection and characterization of interstitial infiltrates on chest radiographs.

Key words: Computer-aided diagnosis(CAD), Chest radiograph, Interstitial infiltrate, Gray-level run length