Evaluation of JPEG and JPEG2000 compression algorithms for dermatological images

Evaluation of High-Efficiency Image Coding algorithm for dermatology images in teledermatology

BACKGROUND

Currently, teledermatology assumes a progressively greater role in the modern healthcare system, especially in consultation, diagnosis, or examining lesions and skin cancers. One of the major challenges facing teledermatology systems is determining the optimal image compression method to efficiently reduce the space needed for electronic storage and data transmission.

OBJECTIVE

To the objective and subjective assessment of HEIC compression method on dermatological color images and benchmarking the performance of High-Efficiency Image Coding (HEIC) with different algorithms to a feasibility study of the method for teledermatology.

METHODS

Twenty-five clinical and five skin histopathology images were taken in department of dermatology, Imam Reza Hospital, Mashhad, Iran. For each image, a set of 24 compressed images with different compression rates, which is composed of eight JPEG, eight JPEG2000, and eight HEIC images, has been prepared. Compressed and original images were shown simultaneously to three dermatologists and one dermatopathologist with different experiences. Each dermatologist scored quality and suitability of compressed images for diagnostic, as well as educational/scientific purposes. An objective evaluation was performed by calculating the mean "distance" of pixel colors and peak signal-to-noise ratio (PSNR).

RESULTS

All compression rates for HEIC were objectively better than JPEG and JPEG2000, particularly at PSNR. Moreover, mean "color distance" per pixel for compressed images using HEIC was lower than others. The subjective image quality assessment also confirms the results of objective evaluation. In both educational and clinical diagnostic applications, HEIC compressed images have the highest score.

CONCLUSION

In consideration of objective and subjective evaluation, the HEIC algorithm represents an optimal performance in dermatology images compression compared with JPEG and JPEG2000.

Standardising and assessing digital images for use in clinical trials: a practical, reproducible method that blinds the assessor to treatment allocation

With the increasing availability of high quality digital cameras that are easily operated by the non-professional photographer, the utility of using digital images to assess endpoints in clinical research of skin lesions has growing acceptance. However, rigorous protocols and description of experiences for digital image collection and assessment are not readily available, particularly for research conducted in remote settings. We describe the development and evaluation of a protocol for digital image collection by the non-professional photographer in a remote setting research trial, together with a novel methodology for assessment of clinical outcomes by an expert panel blinded to treatment allocation.

JPEG vs. JPEG2000: benchmarking with dermatological images

BACKGROUND

Despite the importance of images in the discipline and the diffusion of digital imaging devices, the issue of image compression in dermatology was discussed only in few studies, which yielded results often not comparable, and left some unanswered questions.

OBJECTIVE

To evaluate and compare the performance of the JPEG and JPEG2000 algorithms for compression of dermatological images.

METHODS

Nineteen macroscopic and fifteen videomicroscopic images of skin lesions were compressed with JPEG and JPEG2000 at 18 different compression rates, from 90% to 99.5%. Compressed images were shown, next to uncompressed versions, to three dermatologists with different experience, who judged quality and suitability for educational/scientific and diagnostic purposes. Moreover, alterations and quality were evaluated by calculation of mean 'distance' of pixel colors between compressed and original images and by peak signal-to-noise ratio, respectively.

RESULTS

JPEG2000 was qualitatively better than JPEG at all compression rates, particularly highest ones, as shown by dermatologists' ratings and objective parameters. Agreement between raters was high, but with some differences in specific cases, showing that different professional experience can influence judgement on images.

CONCLUSION

In consideration of its high qualitative performance and wide diffusion, JPEG2000 represents an optimal solution for the compression of digital dermatological images.