Skin cancer detection by deep learning and sound analysis algorithms: A prospective clinical study of an elementary dermoscope

A Dascalu, E O David, A Dascalu, E O David

Abstract

Background: Skin cancer (SC), especially melanoma, is a growing public health burden. Experimental studies have indicated a potential diagnostic role for deep learning (DL) algorithms in identifying SC at varying sensitivities. Previously, it was demonstrated that diagnostics by dermoscopy are improved by applying an additional sonification (data to sound waves conversion) layer on DL algorithms. The aim of the study was to determine the impact of image quality on accuracy of diagnosis by sonification employing a rudimentary skin magnifier with polarized light (SMP).

Methods: Dermoscopy images acquired by SMP were processed by a first deep learning algorithm and sonified. Audio output was further analyzed by a different secondary DL. Study criteria outcomes of SMP were specificity and sensitivity, which were further processed by a F2-score, i.e. applying a twice extra weight to sensitivity over positive predictive values.

Findings: Patients (n = 73) fulfilling inclusion criteria were referred to biopsy. SMP analysis metrics resulted in a receiver operator characteristic curve AUC's of 0.814 (95% CI, 0.798-0.831). SMP achieved a F2-score sensitivity of 91.7%, specificity of 41.8% and positive predictive value of 57.3%. Diagnosing the same set of patients' lesions by an advanced dermoscope resulted in a F2-score sensitivity of 89.5%, specificity of 57.8% and a positive predictive value of 59.9% (P=NS).

Interpretation: DL processing of dermoscopic images followed by sonification results in an accurate diagnostic output for SMP, implying that the quality of the dermoscope is not the major factor influencing DL diagnosis of skin cancer. Present system might assist all healthcare providers as a feasible computer-assisted detection system. FUND: Bostel Technologies. Trial Registration clinicaltrials.gov Identifier: NCT03362138.

Keywords: Artificial intelligence; Deep learning; Dermoscopy; Melanoma; Skin cancer; Sonification; Telemedicine.

Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.

Figures

Fig. 1
Fig. 1
Flowchart of image processing. A dermoscopy image is acquired by a smartphone and conveyed to cloud computing. A deep learning classifier predicts primary findings which are further processed by sonification. Final diagnosis is conferred to user as a malign or benign lesion diagnosis, i.e. excise or not indication.
Fig. 2
Fig. 2
An image from an elementary dermoscope (2a) was compared to the advanced dermoscope version (2b). A Fast Fourier Transformation was applied on images (2c, b), white areas were further thresholded (Fig. 2e, f) and area fraction was measured. The advanced dermoscope possesses higher spatial frequencies (p > .001) and therefore inputs a more detailed image.
Fig. 3
Fig. 3
Comparison of benign nevus (left), dysplastic nevus (middle) and melanoma (right). A. Skin magnifier with polarized light acquires hazy out of focus images, without a clear-cut pattern recognition of fine details required for diagnosis. B. Same lesions images acquired by an advanced dermoscope exhibit clear fine features and edges enabling diagnosis. C. Raw audio waves of a benign nevus, dysplastic nevus and melanoma, imperceptible to the human eye.
Fig. 4
Fig. 4
ROC curve of raw sonified audio files derived from an elementary dermoscope.

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