Quantitative and kinetic evolution of wound healing through image analysis

Application of deep learning to pressure injury staging

OBJECTIVE

Accurate assessment of pressure injuries (PIs) is necessary for a good outcome. Junior and non-specialist nurses have less experience with PIs and lack clinical practice, and so have difficulty staging them accurately. In this work, a deep learning-based system for PI staging and tissue classification is proposed to help improve its accuracy and efficiency in clinical practice, and save healthcare costs.

METHOD

A total of 1610 cases of PI and their corresponding photographs were collected from clinical practice, and each sample was accurately staged and the tissues labelled by experts for training a Mask Region-based Convolutional Neural Network (Mask R-CNN, Facebook Artificial Intelligence Research, Meta, US) object detection and instance segmentation network. A recognition system was set up to automatically stage and classify the tissues of the remotely uploaded PI photographs.

RESULTS

On a test set of 100 samples, the average precision of this model for stage recognition reached 0.603, which exceeded that of the medical personnel involved in the comparative evaluation, including an enterostomal therapist.

CONCLUSION

In this study, the deep learning-based PI staging system achieved the evaluation performance of a nurse with professional training in wound care. This low-cost system could help overcome the difficulty of identifying PIs by junior and non-specialist nurses, and provide valuable auxiliary clinical information.

Diagnostic and Prognostic Utility of Non-Invasive Multimodal Imaging in Chronic Wound Monitoring: a Systematic Review

Monitoring chronic wound [CW] healing is a challenging issue for clinicians across the world. Moreover, the health and cost burden of CW are escalating at a disturbing rate due to a global rise in population of elderly and diabetic cases. The conventional approach includes visual contour, sketches, or more rarely tracings. However, such conventional techniques bring forth infection, pain, allergies. Furthermore, these methods are subjective as well as time-consuming. As such, nowadays, non-touching and non-invasive CW monitoring system based on imaging techniques are gaining importance. They not only reduce patients' discomfort but also provide rapid wound diagnosis and prognosis. This review provides a survey of different types of CW characteristics, their healing mechanism and the multimodal non-invasive imaging methods that have been used for their diagnosis and prognosis. Current clinical practices as well as personal health systems [m-health and e-health] for CW monitoring have been discussed.

3D hybrid wound devices for spatiotemporally controlled release kinetics

This paper presents localized and temporal control of release kinetics over 3-dimensional (3D) hybrid wound devices to improve wound-healing process. Imaging study is performed to extract wound bed geometry in 3D. Non-Uniform Rational B-Splines (NURBS) based surface lofting is applied to generate functionally graded regions. Diffusion-based release kinetics model is developed to predict time-based release of loaded modifiers for functionally graded regions. Multi-chamber single nozzle solid freeform dispensing system is used to fabricate wound devices with controlled dispensing concentration. Spatiotemporal control of biological modifiers thus enables a way to achieve target delivery to improve wound healing.

Wound healing assessment: does the ideal methodology for a research setting exist?

INTRODUCTION

Studies on dressings frequently measure wound healing to demonstrate performance. Knowledge of existing methodologies available for wound healing assessment, including their advantages and limitations, is paramount when evaluating the literature on dressings.

METHODOLOGY

Medline and Cochrane databases were searched for wound healing assessment methodologies used in research or in clinical practice.

RESULTS

Twenty-nine methodologies were identified and classified into 8 categories: scales (n = 4), one-dimensional measurements (n = 2), area measurements (n = 4), volume measurements (n = 6), 3-dimensional wound reproduction systems (n = 5), methodologies based on wound physical characteristics (n = 3), rates and surrogates end point calculated from variation in wound dimensions (n = 4), and time to wound healing (n = 1). The main problems encountered during wound healing assessment include the following: boundary definition, assessor's contact with the wound, irregular wound shape, and difficulty in evaluating early healing.

CONCLUSION

At this time, an ideal methodology does not exist. Research in this area is lacking and should be the focus in wound healing evaluation.

Reflectance measurement using digital camera and a protecting dome with built in light source

The reflectance of the skin reveals the chemical and physical changes of the skin as well as many metabolic changes. The reflectance measurement is an important method for medical diagnosis, follow-up and screening. This article concentrates on designing and validating an imaging system, based on a digital camera. The proposed system can measure the reflectance of the skin with high spatial and currently four channel spectral resolution, in the range of 450 nm to 980 nm. The accuracy of the system is determined by imaging a colour checker board and comparing the obtained values with both given values and spectrometer measurements. The diffuse interreflections of both, the integrating sphere and the lighting dome of the imaging system, is compensated with a correction factor. The accuracy of the proposed system is only slightly weaker than the spectrometer. The imaging system characteristics are independent of the camera characteristics.

Automatic evaluation of pressure sore status by combining information obtained from high-frequency ultrasound and digital photography

In this study, the different phases of pressure sore generation and healing are investigated through a combined analysis of high-frequency ultrasound (20 MHz) images and digital color photographs. Pressure sores were artificially induced in guinea pigs, and the injured regions were monitored for 21 days (data were obtained on days 3, 7, 14, and 21). Several statistical features of the images were extracted, relating to both the altering pattern of tissue and its superficial appearance. The features were grouped into five independent categories, and each category was used to train a neural network whose outputs were the four days. The outputs of the five classifiers were then fused using a fuzzy integral to provide the final decision. We demonstrate that the suggested method provides a better decision regarding tissue status than using either imaging technique separately. This new approach may be a viable tool for detecting the phases of pressure sore generation and healing in clinical settings.

Automatic colorimetric calibration of human wounds

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

1^st 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.

Three-dimensional assessment of skin wounds using a standard digital camera

In this paper, after an overview of the literature concerning the imaging technologies applied to skin wounds assessment, we present an original approach to build 3-D models of skin wounds from color images. The method can deal with uncalibrated images acquired with a handheld digital camera with free zooming. Compared with the cumbersome imaging systems already proposed, this novel solution uses a low-cost and user-friendly image acquisition device suitable for widespread application in health care centers. However, this method entails the development of a robust image processing chain. An original iterative matching scheme is used to generate a dense estimation of the surface geometry from two widely separated views. The best configuration for taking photographs lies between 15 ( degrees ) and 30 ( degrees ) for the vergency angle. The metric reconstruction of the skin wound is fully automated through self-calibration. From the 3-D model of the skin wound, accurate volumetric measurements are achieved. The accuracy of the inferred 3-D surface is validated by registration to a ground truth and repetitive tests on volume. The global precision around 3% is in accordance with the clinical requirement of 5% for assessing the healing process.

Occlusive dressings and the healing of standardized abrasions

CONTEXT

Acute skin trauma during sport participation, resulting in partial-thickness abrasions, is common. The limited investigations focusing on the acute wound environment and dressing techniques and the subsequent lack of evidence-based standards complicate clinical wound care decisions.

OBJECTIVE

To examine the effects of occlusive dressings on healing of standardized, partial-thickness abrasions.

DESIGN

Controlled, counterbalanced, repeated-measures design.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Sixteen healthy women (n = 10) and men (n = 6).

INTERVENTION(S)

Four standardized, partial-thickness abrasions were inflicted. Film, hydrogel, and hydrocolloid occlusive dressings and no dressing (control) were applied. Participants returned on postwound days 1, 3, 5, 7, 10, and 14 for digital imaging. Wound healing time was measured by change in wound contraction (cm(2)) and change in wound color (chromatic red) and luminance in red, green, and blue color values.

MAIN OUTCOME MEASURE(S)

Wound contraction, color (chromatic red), and luminance.

RESULTS

A day-by-dressing interaction was found for wound contraction, color, and luminance. Post hoc testing indicated that the film and hydrocolloid dressings produced greater wound contraction than the hydrogel and no dressing on days 7 and 10. Film, hydrogel, and hydrocolloid dressings also resulted in greater wound contraction than the control on day 14. Hydrocolloid dressings produced smaller measures of color and greater measures of luminance than no dressing on day 7. Film, hydrogel, and hydrocolloid dressings also resulted in smaller measures of color and greater measures of luminance compared with no dressing on days 10 and 14.

CONCLUSIONS

When compared with the control (no dressing), the film, hydrogel, and hydrocolloid occlusive dressings were associated with a faster healing rate of partial-thickness abrasions across time measured by wound contraction, color, and luminance. Overall, these data indicate that occlusive dressings were more effective in healing than no dressing was.

3D modeling from uncalibrated color images for a complete wound assessment tool

This paper is concerned with the 3D modeling of skin wound using uncalibrated vision techniques for the volumetric assessment of the healing process. We have developed an original approach for matching two color images captured with a free-handled digital camera and generate a semi-dense 3D model. We evaluate the precision of the inferred 3D model by registration to a ground truth on artificial wounds. The method is then applied to volumetric measurements. The clinician requirements of a global 5% precision are overshot as 3% is obtained locally. The best configuration for taking photos lies between 1.2 and 1.5 for distance ratios and between 15 degrees and 30 degrees for vergence of the stereo pair. This work is part of the ESCALE project dedicated to the design of a complete 3D and color wound assessment tool using a simple free handled digital camera: a smart solution for massive diffusion in care centers as such very low cost system should be operated directly by nurses.

A computer assisted diagnosis tool for the classification of burns by depth of injury

In this paper, a computer assisted diagnosis (CAD) tool for the classification of burns into their depths is proposed. The aim of the system is to separate burn wounds from healthy skin, and to distinguish among the different types of burns (burn depths) by means of digital photographs. It is intended to be used as an aid to diagnosis in local medical centres, where there is a lack of specialists. Another potential use of the system is as an educational tool. The system is based on the analysis of digital photographs. It extracts from those images colour and texture information, as these are the characteristics observed by physicians in order to form a diagnosis. Clinical effectiveness of the method was demonstrated on 35 clinical burn wound images, yielding an average classification success rate of 88% compared to expert classified images.

Segmentation and classification of burn images by color and texture information

In this paper, a burn color image segmentation and classification system is proposed. The aim of the system is to separate burn wounds from healthy skin, and to distinguish among the different types of burns (burn depths). Digital color photographs are used as inputs to the system. The system is based on color and texture information, since these are the characteristics observed by physicians in order to form a diagnosis. A perceptually uniform color space (L*u*v*) was used, since Euclidean distances calculated in this space correspond to perceptual color differences. After the burn is segmented, a set of color and texture features is calculated that serves as the input to a Fuzzy-ARTMAP neural network. The neural network classifies burns into three types of burn depths: superficial dermal, deep dermal, and full thickness. Clinical effectiveness of the method was demonstrated on 62 clinical burn wound images, yielding an average classification success rate of 82%.

Wound healing: a multidisciplinary approach for dermatologists

This article has provided a review of common and some less common approaches to wound healing. Chronic wound healing is one of the more challenging areas of medicine, with a nice balance of the science and art of medicine. An evidence-based, patient-centered approach can be used to effectively improve the care of many difficult to heal ulcers in often frustrated patients. The multidisciplinary wound clinic concept can work to improve the outcomes of patients with leg ulcers.