An imaging system with calibrated color image acquisition for use in dermatology.
We propose a novel imaging system useful in dermatology, more precisely, for the follow-up of patients with an increased risk of skin cancer. The system consists of a Pentium PC equipped with an RGB frame grabber, a three-chip charge coupled devices (CCD) camera controlled by the serial port and equipped with a zoom lens and a halogen annular light source. Calibration of the imaging system provides a way to transform the acquired images, which are defined in an unknown color space, to a standard, well-defined color space called sRGB. sRGB has a known relation to the CIE1 XYZ and CIE L*a*b* colorimetric spaces. These CIE color spaces are based on the human vision, and they allow the computation of a color difference metric called CIE deltaE*ab, which is proportional to the color difference, as seen by a human observer. Several types of polynomial RGB to sRGB transforms will be tried, including some optimized in perceptually uniform color spaces. The use of a standard and well-defined color space also allows meaningful exchange of images, e.g., in teledermatology. The calibration procedure is based on 24 patches with known color properties, and it takes about 5 minutes to perform. It results in a number of settings called a profile that remains valid for tens of hours of operation. Such a profile is checked before acquiring images using just one color patch, and is adjusted on the fly to compensate for short-term drift in the response of the imaging system. Precision or reproducibility of subsequent color measurements is very good with (deltaE*ab) = 0.3 and deltaE*ab < 1.2. Accuracy compared with spectrophotometric measurements is fair with (deltaE*ab) = 6.2 and deltaE*ab < 13.3.
Vander Haeghen
Y
Y
Department of Engineering, ELIS-MEDISIP, University Gent, Belgium. yves.vanderhaeghen@rug.ac.be
Naeyaert
J M
JM
Lemahieu
I
I
Philips
W
W
D002138:Calibration; D003116:Color; D003626:Data Display; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D010781:Photography / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012867:Skin / Q000473:pathology; D012878:Skin Neoplasms / Q000473:pathology*