Projection profile analysis for identifying different views of chest radiographs.
OBJECTIVE
For computerized analysis of chest images in the clinical environment, identification of frontal (posteroanterior/anteroposterior) and lateral chest radiographs is an important preprocessing step. In this study, we developed a method to distinguish frontal from lateral views of the chest radiographs based on an analysis of the projection profile.


METHODS
Projection profile is obtained by projecting a chest image on to the mediolateral axis. Two indices, body symmetry index and background percentage index, are computed from the projection profile. The combination of body symmetry index and background percentage index is used to determine the view of chest radiographs. The method is evaluated on a sample of 2000 frontal and 1000 lateral chest images.


RESULTS
The values of body symmetry index are found to be 1.18 +/- 0.23 and 3.07 +/- 1.42 for frontal and lateral chest images, respectively. The values of background percentage index are found to be 0.03 +/- 0.05 and 0.33 +/- 0.09 for frontal and lateral chest images, respectively. The discrimination is evaluated by linear discriminant analysis and receiver operating characteristic analysis. Area Az under the receiver operating characteristic curve with the combination of the two indices is 0.993.


CONCLUSIONS
The method can be used as a preprocessing step for further analysis in chest radiographs.
Kao
E-Fong
EF
Department of Computer Science and Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC. tonykao@ms12.url.com.tw
Lee
Chungnan
C
Jaw
Twei-Shiun
TS
Hsu
Jui-Sheng
JS
Liu
Gin-Chung
GC
D000465:Algorithms; D001185:Artificial Intelligence; D016247:Information Storage and Retrieval / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013902:Radiography, Thoracic / Q000145:classification* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity