Digital imaging techniques in dermatology

Diagnostics Using Non-Invasive Technologies in Dermatological Oncology

The growing incidence of skin cancer, with its associated mortality and morbidity, has in recent years led to the developing of new non-invasive technologies, which allow an earlier and more accurate diagnosis. Some of these, such as digital photography, 2D and 3D total-body photography and dermoscopy are now widely used and others, such as reflectance confocal microscopy and optical coherence tomography, are limited to a few academic and referral skin cancer centers because of their cost or the long training period required. Health care professionals involved in the treatment of patients with skin cancer need to know the implications and benefits of new non-invasive technologies for dermatological oncology. In this article we review the characteristics and usability of the main diagnostic imaging methods available today.

Perception and Acceptability of Medical Photography in Chinese Dermatologic Patients: A Questionnaire Survey

BACKGROUND

Medical photography is increasingly used by physicians, but studies assessing the perception and acceptability of medical photography by Chinese dermatologic patients are scarce.

OBJECTIVE

To assess the perception and acceptability of medical photography in Chinese dermatologic patients.

MATERIALS AND METHODS

From July to December 2014, adult patients visiting the Dermatology Clinic of The First Affiliated Hospital of Third Military Medical University were included in this study. They were required to fill an anonymous questionnaire regarding perception and acceptability of medical photography.

RESULTS

A total of 509 consecutive patients completed the questionnaire, with 35 and 474 declining and undergoing medical photography, respectively. Meanwhile, 81.0% of the patients preferred to be photographed by attending physicians; 63.3% favored clinic-owned cameras, and 81.0% would rather have their photographs stored in the department's database. Besides, most patients allowed their photographs to be used in case studies (92.8%) or medical record keeping (90.3%).

CONCLUSION

Most Chinese dermatologic patients accept medical photography. However, the principles of privacy protection and informed consent should be strictly enforced in clinical practice, and appropriate photographic devices and storage methods should be used, for better acceptance.

Integrating digital image management software for improved patient care and optimal practice management

BACKGROUND

Photographic images provide vital documentation of preoperative, intraoperative, and postoperative results in the clinical dermatologic surgery practice and can document histologic findings from skin biopsies, thereby enhancing patient care. Images may be printed as part of text documents, transmitted via electronic mail, or included in electronic medical records.

OBJECTIVES

To describe existing computer software that integrates digital photography and the medical record to improve patient care and practice management.

CONCLUSIONS

A variety of computer applications are available to optimize the use of digital images in the dermatologic practice.

Digital dermoscopy analysis of atypical pigmented skin lesions: a stepwise logistic discriminant analysis approach

BACKGROUND

Digital microscopy is a non-invasive diagnostic technique enabling determination of characteristics that cannot be appreciated by direct observation. If correctly applied, this technique can be useful for the diagnosis of pigmented skin lesions.

PURPOSE

To evaluate the utility of digital microscopy for analysing atypical benign and malignant pigmented skin lesions exploiting digital numerical filtering and automatic measurements.

METHODS

Forty-eight parameters were identified as possible discriminating variables, and were grouped in four categories: geometries, colours, textures, and islands of colour. Statistical analysis was used to identify the variables with the highest discriminating power.

RESULTS

The high quality of the digital image made it possible to observe diagnostic signs in pigmented skin lesion images, acquired by the present technique, in great detail. Specially designed filtering enhanced certain diagnostic patterns. Stepwise discriminant analysis selected only 10 variables (the means of these variables were higher in melanomas than in nevi).

CONCLUSIONS

The combined use of digital dermoscopy and stepwise logistic discriminant analysis made it possible to single out the best objective variables for distinguishing atypical nevi and early melanoma.

Intravenous lidocaine infusion in the treatment of experimental human skin burns - digital colour image analysis of erythema development

Previous studies have shown that local anaesthetics possess a wide range of effects on the pathophysiology of burns, including inhibition of burn oedema and inhibition of progressive burn ischemia. The present randomised double-blind cross-over study in six volunteers investigated the effects of intravenous lidocaine infusion on partial thickness skin burns. A thermoprobe was used to induce a standardised thermal injury (1 cm(2)) on the flexor side of one forearm and was repeated on the opposite side 1 week later. Subjects received either an intravenous bolus dose of lidocaine (1 mg kg(-1)) immediately after the thermal trauma followed by continuous intravenous infusion of lidocaine (40 microg kg(-1) min(-1)) during 4 h or equal volumes of isotonic saline. Macrophotographs of the experimental skin area were taken preburn and 1, 2, 3, 4, and 12 h postburn and evaluated by computerised image colour analysis using normalised rgb (n-rgb) and Hue-Saturation-Intensity (HSI) colour systems as a quantitative measure of pathophysiological events. Maximum erythema occurred 2-3 h postburn. Differences between lidocaine- and placebo-treated burns were not significant during the first 4 h postburn. At 12 h postburn, the lidocaine-treated burn demonstrated a significantly faster restitution of residual erythema compared to control sites. The present study shows that intravenous lidocaine significantly inhibits the long-term inflammation-induced tissue responses to thermal trauma.

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.

The uses of digital photography in dermatology

Digital photography is a powerful tool that is transforming the specialty of dermatology by integrating patient and practice management. The fundamentals of digital imaging are discussed, and an approach to the selection of a digital camera and its associated hardware and software is provided. The applications of this technology to patient and practice management are addressed, and the ethical implications of digital tampering are also discussed.

Digital image analysis of erythema development after experimental thermal injury to human skin: effect of postburn topical local anesthetics (EMLA)

Local anesthetics inhibit edema and improve circulation in experimental burns. We evaluated the effect of topical local anesthetics on human skin burns in volunteers using computerized color analysis that allowed repeated noninvasive quantitative measurements. A standardized partial-thickness burn (1 cm2) was induced in one forearm of 10 healthy volunteers and in the opposite forearm a week later. The burned areas were treated with lidocaine/prilocaine cream (EMLA; Astra, Sweden) or a placebo cream for 1 h. The experimental skin area was photographed before and 1, 2, 4, and 12 h postburn. Digitized images were evaluated using normalized red-green-blue and Hue-Saturation-Intensity. Differences in erythema between skin treated with EMLA and placebo were not significant during the first 4 h postburn. However, 12 h postburn, a pronounced decrease in the degree of erythema was observed in EMLA-treated skin compared with placebo-treated skin. We conclude that topical local anesthetics administered for 1 h postburn significantly reduces the duration of erythema after a mild thermal injury, which suggests a potential use in clinical practice in the treatment of minor skin burns.

IMPLICATIONS

Burn injury constitutes a serious type of tissue damage that activates inflammatory mechanisms, often causing pain, disfiguration, or malfunction. We treated burns using an anesthetic cream and demonstrated a reduction in burn-induced inflammation by using computer-based color image analysis.

Remote interpretation of microbiology specimens based on transmitted still images

A pilot study was carried out to examine the feasibility of the remote interpretation of microbiology specimens, that is, micro-organisms grown on agar in Petri dishes. The objective of our study was to decide whether still images contained enough information for microbiology specialists to identify the microorganisms accurately. A representative sample of microbiology specimens grown on the most commonly used agar media was used. Still images were captured using a video camera and a PC-based system. The results from a pilot study with the first video camera were discouraging, the interpretations differing in five out of 22 specimens; results with a second video camera were also disappointing. Images were then captured on photographic film, at a considerably higher resolution than images captured by the digitizer board in the PC. Again, however, the results were disappointing. We conclude that interpretation of microbiology specimens based exclusively on visual information is problematical. Remote microbiology interpretation in the future will require images of higher information content (e.g., including three-dimensional information), and will probably require additional information as well, from other senses, such as smell.

Improvement of monitoring of melanocytic skin lesions with the use of a computerized acquisition and surveillance unit with a skin surface microscopic television camera

BACKGROUND

Photographic documentation of melanocytic skin lesions is important. Storage and retrieval of slides, however, take much time and space.

OBJECTIVE

Our purpose was to develop and clinically test a computerized acquisition and surveillance (CAS) unit with a television camera for monitoring including measurements of lesional areas.

METHODS

A CAS unit connected with a skin surface microscopic television camera was used for monitoring of melanocytic nevi (MN). The lesional area and the skin surface microscopic appearance (SMA) were analyzed after 10 to 21 months in 54 of 1355 MN.

RESULTS

In 19 MN (35.2%), changes were found. In eight cases, changes in size of more or less than 15% were detected; in five cases only the SMA changed. In six cases both characteristics changed.

CONCLUSION

In approximately 25% of MN, changes were only detectable in the SMA but not with area measurements. This favors the use of systems such as CAS because only they allow a time-saving comparison of actual and previous images.

Digital image analysis (DIA) of colour changes in human skin exposed to standardized thermal injury and comparison with laser Doppler measurements

Clinical macrophotography followed by digitization and computer-assisted image analysis was performed on volunteers exposed to a mild experimental thermal injury. The aim was to elaborate a non-invasive technique allowing repetitive and quantitative monitoring of induced erythema and to evaluate a possible relationship with laser Doppler measurement of skin perfusion. A standardized 1 x 1 cm large thermal trauma was induced in the skin of the ventral forearm of 12 volunteers. Photographic recordings and skin blood flow measurements were made preburn and at 30-min, 1-h, 2-h, 4-h and 12-h postburn. Image analysis was performed with two colour systems, normalized rgb-values (rgb) and Hue-Saturation-Intensity (HSI). Erythema measured by rgb and HSI was most pronounced during the first hour postburn, after which it gradually decreased in order to increase again at 12 h postburn. Skin perfusion peaked at 30 min postburn and then continuously decreased during the course of the experiments. Degree of erythema could be quantified using both colour systems and a linear relationship was obtained between the observed colour changes of both systems and changes in skin perfusion. Results may also indicate that erythema can be present without a concomitant increase in skin perfusion, probably representing postburn venous stasis. The present study showed that digital image analysis is a non-invasive technique allowing repetitive and quantitative analysis of skin erythema which can be used to monitor pathophysiological changes in the body as well as the result of their treatment.

Intraobserver agreement in interpretation of digital epiluminescence microscopy

BACKGROUND

Although a major problem with the classification of epiluminescence microscopy (ELM) findings is the lack of standard definitions, reproducibility of the criteria proposed has never been investigated.

OBJECTIVES

Our purposes were (1) to perform a review of four major published classifications to obtain a set of apparently well-defined ELM variables and descriptors and (2) to evaluate the ability of one of us to report consistently ELM findings in melanocytic lesions according to these criteria.

METHODS

Intraobserver agreement (with a set of 44 selected descriptors) between two readings of 150 digital ELM images was evaluated with the kappa (kappa) statistic. Subgroups of descriptors were compared for kappa value distribution.

RESULTS

The median kappa value for the whole series of descriptors was 0.66. Median kappa did not vary significantly among the four classification systems (kappa = 0.61 to 0.67). Agreement was significantly better as to the presence or absence of ELM findings (kappa range, 0.39 to 1.00; median kappa, 0.77) compared with agreement as to their distribution (kappa range, 0.10 to 0.79; median kappa, 0.47; p = 0.0007) and their width, thickness, and size (kappa range, 0.06 to 0.83; median kappa, 0.39; p = 0.0075).

CONCLUSION

Although nothing can be inferred from a single study, descriptors associated with low intraobserver agreement are likely to be inadequately defined.

Computerized digital image analysis: an aid for melanoma diagnosis--preliminary investigations and brief review

Both digital imaging and epiluminescence microscopy hold promise for improved early detection of cutaneous melanoma. Several centers have been actively working in these areas during the past decade. These experiences and preliminary work based on the image capture of 83 pigmented lesions at our center using a prototype digital imaging system (SKINVIEW) are described. This system is based, in part, on the analysis of lesional morphologic features, such as shape, border, and radii. Histopathologic correlation was matched against these features to assess the efficacy of diagnosis. At our center, these parameters alone were not sufficient to discriminate between benign and malignant lesions, in part, because the melanomas were, in general, early lesions and many of the nevi were sufficiently clinically atypical to require removal for discrimination from melanoma. In addition, technical improvements in the image capturing and processing mechanism are needed. Rapid progress in this area is anticipated.

Evaluation of different image acquisition techniques for a computer vision system in the diagnosis of malignant melanoma

BACKGROUND

Digital image analysis was found to be a useful technique for improved accuracy of preoperative diagnosis of melanocytic lesions. In previous studies digitized color slides were used as input for digital image analysis. New technologies and smaller video cameras made it possible to develop a camera system that allows the digitization of skin lesions directly from the patient.

OBJECTIVE

We investigated whether conventional color slides or directly digitized images should be used for a reliable recognition of malignant melanoma.

METHODS

Computer features describing characteristics of the lesions were computed for 404 digitized color slides and for 309 directly acquired lesions. Statistical analysis and classifier construction was performed by the commercial statistical classification program CART.

RESULTS

With the data set derived either from the color slides or from the directly digitized lesions a sensitivity of about 90% for the recognition of malignant melanoma could be obtained.

CONCLUSION

Both image acquisition techniques allow a reliable detection of malignant melanoma and both are appropriate as input for an image analysis system regarding its efficiency as a diagnostic tool. However, none of the classifiers can be applied with reasonable significance to both techniques.

Photography without film: low-cost digital cameras come of age in dermatology

BACKGROUND

Photography is integral to the practice of dermatology. Digital imaging techniques have only recently been used to assess cutaneous disorders. Previously reported imaging systems have been both expensive and cumbersome. Consequently, they have failed to gain wide-spread acceptance.

METHODS

We describe our experience using an inexpensive digital camera. Photographs taken with this portable digital camera (FotoMan) compare favorably to those obtained with conventional 35 mm cameras.

RESULTS

This inexpensive digital camera provides photographs of acceptable quality for a variety of dermatologic applications. Images created with this system are available within minutes and are less expensive than traditional photographs.

CONCLUSIONS

Digital imaging is a new and exciting development. The digital camera described is simple to operate and provides a useful alternative or adjunct to conventional photography.