Psychophysical evaluation of calibration curve for diagnostic LCD monitor.
OBJECTIVE
In 1998, Digital Imaging Communications in Medicine (DICOM) proposed a calibration tool, the grayscale standard display function (GSDF), to obtain output consistency of radiographs. To our knowledge, there have been no previous reports of investigating the relation between perceptual linearity and detectability on a calibration curve.


METHODS
To determine a suitable calibration curve for diagnostic liquid crystal display (LCD) monitors, the GSDF and Commission Internationale de l'Eclairage (CIE) curves were compared using psychophysical gradient delta and receiver operating characteristic (ROC) analysis for clinical images.


RESULTS
We succeeded in expressing visually recognized contrast directly using delta instead of the just noticeable difference (JND) index of the DICOM standard. As a result, we found that the visually recognized contrast at low luminance areas on the LCD monitor calibrated by the CIE curve is higher than that calibrated by the GSDF curve. On the ROC analysis, there was no significant difference in tumor detectability between GSDF and CIE curves for clinical thoracic images. However, the area parameter Az of the CIE curve is superior to that of the GSDF curve. The detectability of tumor shadows in the thoracic region on clinical images using the CIE curve was superior to that using the GSDF curve owing to the high absolute value of delta in the low luminance range.


CONCLUSIONS
We conclude that the CIE curve is the most suitable tool for calibrating diagnostic LCD monitors, rather than the GSDF curve.
Uemura
Masanobu
M
Department of Central Radiology, Kinki University Hospital, 377-2 Ohnohigashi, Osaka-Sayama 589-8511, Japan. uemura@radt.med.kindai.ac.jp
Asai
Yoshiyuki
Y
Yamaguchi
Michihiro
M
Fujita
Hideki
H
Shintani
Yuuko
Y
Sanada
Shigeru
S
D002138:Calibration; D016288:Computer Terminals / Q000592:standards*; D006801:Humans; D050866:Liquid Crystals; D011601:Psychophysics / Q000592:standards*; D012372:ROC Curve; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000592:standards*; D012015:Reference Standards