[ROC analysis of detection of interval changes in interstitial lung diseases on digital chest radiographs using the temporal subtraction technique].
OBJECTIVE
To demonstrate the clinical usefulness of a temporal subtraction technique for the detection of interval changes in various interstitial lung diseases on digital chest radiographs.


METHODS
One hundred pairs of chest radiographs in 34 patients (63 with and 37 without interval changes) with various interstitial lung diseases were selected. All cases were confirmed by serial chest computed tomography (CT) and ascertained by radiologists. All chest radiographs were obtained with a computed radiography (CR) system, and temporal subtraction images were produced with an iterative image-warping technique. Four radiologists and two thoracic physicians provided confidence levels for interval changes in interstitial lung diseases with and without temporal subtraction. Their performances with and without temporal subtraction were evaluated by means of receiver operating characteristic (ROC) analysis using a sequential test.


RESULTS
The area under the ROC curve (Az) values of six observers obtained with and without temporal subtraction were 0.90 and 0.78, respectively. Results showed that the detection of interval changes in interstitial lung diseases was significantly improved by the use of temporal subtraction images compared with CR images alone(P = 0.002). Furthermore, the high detection rate was achieved with temporal subtraction images regardless of the subtlety and location of interval changes.


CONCLUSIONS
Temporal subtraction improved the diagnostic accuracy of radiologists in detecting interval changes in interstitial lung diseases on chest radiographs. It was also useful for cases of multiple interval changes.
Department of Radiological Sciences, School of Health Sciences, Faculty of Medicine, Kyushu University.
Yoshiharu
Y
Higashida
Tadamitsu
T
Ideguchi
Toru
T
Muranaka
Nobuyuki
N
Tabata
Ryuichi
R
Miyajima
Fumio
F
Akazawa
Hirotaka
H
Ikeda
Ken
K
Morimoto
Masafumi
M
Ohki
Fukai
F
Toyofuku
Kunio
K
Doi
D000328:Adult; D005260:Female; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011856:Radiographic Image Enhancement; D013902:Radiography, Thoracic / Q000379:methods*; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed