Calibrated LCD/TFT stimulus presentation for visual psychophysics in fMRI.
Standard projection techniques using liquid crystal (LCD) or thin-film transistor (TFT) technology show drastic distortions in luminance and contrast characteristics across the screen and across grey levels. Common luminance measurement and calibration techniques are not applicable in the vicinity of MRI scanners. With the aid of a fibre optic, we measured screen luminances for the full space of screen position and image grey values and on that basis developed a compensation technique that involves both luminance homogenisation and position-dependent gamma correction. By the technique described, images displayed to a subject in functional MRI can be specified with high precision by a matrix of desired luminance values rather than by local grey value.
Strasburger
H
H
Generation Research Program Bad Tölz, Human Studies Center, Ludwig-Maximilians-Universität München, Arzbacherstr. 12, D-83646, Bad Tölz, Germany. strasburger@uni-muenchen.de
Wüstenberg
T
T
Jäncke
L
L
D001931:Brain Mapping; D002138:Calibration / Q000592:standards; D003118:Color Perception; D016288:Computer Terminals / Q000592:standards; D015350:Contrast Sensitivity; D003626:Data Display; D005336:Fiber Optic Technology / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008029:Lighting; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000523:psychology; D010775:Photic Stimulation; D011601:Psychophysics / Q000379:methods*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014173:Transistors, Electronic / Q000592:standards; D014796:Visual Perception / Q000502:physiology*