Improved visualization of stimulated nodules by adaptive enhancement of digital chest radiography.
OBJECTIVE
Although digital radiography of the chest has a wide dynamic range, difficulties still remain in visualizing the acquired images faithfully on gray-scale displays (cathode-ray tube [CRT] displays), which have a much lower level of luminance than film view boxes. We propose an adaptive-enhancement algorithm for digital chest radiography that provides faithful visualization of the chest on the CRT.


METHODS
We investigated the contrast sensitivity of a CRT monitor and developed an image processing algorithm that compresses the dynamic range and enhances image contrast selectively in the mediastinal area and that transforms the gray scale to visualize the image by use of the full effective dynamic range of the CRT. We performed a receiver-operating characteristic (ROC) study by using simulated nodules to evaluate the clinical value of the proposed algorithm.


RESULTS
The processed images provided improved visualization of both mediastinal and lung regions. The area under the ROC curve for retrocardiac or subdiaphragmatic nodule detection increased significantly (from 0.69 to 0.79; P < 0.05). The area under the ROC curve for lung nodule detection also increased (from 0.64 to 0.75; P < 0.1), although not to the level of statistical significance.


CONCLUSIONS
The proposed algorithm allows improved visualization of nodules on digital chest radiographs with the CRT display.
Kim
J H
JH
Department of Radiology, Seoul National University Hospital, South Korea.
Im
J G
JG
Han
M C
MC
Min
B G
BG
Lee
C W
CW
D000465:Algorithms; D003198:Computer Simulation; D004056:Differential Threshold; D005189:False Positive Reactions; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008482:Mediastinum / Q000000981:diagnostic imaging; D008954:Models, Biological; D015588:Observer Variation; D012372:ROC Curve; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*