Automatic colorimetric calibration of human wounds

Contains fulltext : 88431.pdf (publisher's version ) (Open Access)BACKGROUND: Recently, digital photography in medicine is considered an acceptable tool in many clinical domains, e.g. wound care. Although ever higher resolutions are available, reproducibility is still poor and visual comparison of images remains difficult. This is even more the case for measurements performed on such images (colour, area, etc.). This problem is often neglected and images are freely compared and exchanged without further thought. METHODS: The first experiment checked whether camera settings or lighting conditions could negatively affect the quality of colorimetric calibration. Digital images plus a calibration chart were exposed to a variety of conditions. Precision and accuracy of colours after calibration were quantitatively assessed with a probability distribution for perceptual colour differences (dE_ab). The second experiment was designed to assess the impact of the automatic calibration procedure (i.e. chart detection) on real-world measurements. 40 Different images of real wounds were acquired and a region of interest was selected in each image. 3 Rotated versions of each image were automatically calibrated and colour differences were calculated. RESULTS: 1st Experiment: Colour differences between the measurements and real spectrophotometric measurements reveal median dE_ab values respectively 6.40 for the proper patches of calibrated normal images and 17.75 for uncalibrated images demonstrating an important improvement in accuracy after calibration. The reproducibility, visualized by the probability distribution of the dE_ab errors between 2 measurements of the patches of the images has a median of 3.43 dE* for all calibrated images, 23.26 dE_ab for all uncalibrated images. If we restrict ourselves to the proper patches of normal calibrated images the median is only 2.58 dE_ab! Wilcoxon sum-rank testing (p < 0.05) between uncalibrated normal images and calibrated normal images with proper squares were equal to 0 demonstrating a highly significant improvement of reproducibility. In the second experiment, the reproducibility of the chart detection during automatic calibration is presented using a probability distribution of dE_ab errors between 2 measurements of the same ROI. CONCLUSION: The investigators proposed an automatic colour calibration algorithm that ensures reproducible colour content of digital images. Evidence was provided that images taken with commercially available digital cameras can be calibrated independently of any camera settings and illumination features

A new digital image analysis system useful for surface assessment of vitiligo lesions in transplantation studies

So far there is no uniformity in the evaluation methods used in the assessment of treatment outcome in vitiligo studies. The ability to objectively measure surfaces of vitiligo lesions is important for both clinical practice and research. Our objective was to assess the reproducibility, accuracy, user-friendliness and time effectiveness of a new digital image analysis system for surface measurement of vitiligo lesions. Three different observers performed both a visual estimation and a digital image analysis on 30 images of 10 vitiligo lesions. Inter- and intraobserver variation were evaluated and results were compared with the 2D gold standard measurements and a 3D measurement. A high inter- and intra-observer variability was observed for the visual estimation of surfaces. With the digital image analysis system a significant improvement of the reproducibility was achieved (p = 0.01). Moreover, results were accurate and the measurement procedure was user-friendly. Importantly, a systematic underestimation was demonstrated when comparing the 2D with the 3D measurements. We introduced an objective measurement method that might be useful in the future for consistently measuring surfaces of selected vitiligo lesions both before and after different therapeutic modalities

Quantification of myocardial Infarction on PET images

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