Spectroscopic Detection of Caries Lesions.

Background. A caries lesion causes changes in the optical properties of the affected tissue. Currently a caries lesion can be detected only at a relatively late stage of development. Caries diagnosis also suffers from high interobserver variance. Methods. This is a pilot study to test the suitability of an optical diffuse reflectance spectroscopy for caries diagnosis. Reflectance visible/near-infrared spectroscopy (VIS/NIRS) was used to measure caries lesions and healthy enamel on extracted human teeth. The results were analysed with a computational algorithm in order to find a rule-based classification method to detect caries lesions. Results. The classification indicated that the measured points of enamel could be assigned to one of three classes: healthy enamel, a caries lesion, and stained healthy enamel. The features that enabled this were consistent with theory. Conclusions. It seems that spectroscopic measurements can help to reduce false positives at in vitro setting. However, further research is required to evaluate the strength of the evidence for the method's performance.

A review of indocyanine green fluorescent imaging in surgery.

The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

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.

New closed-form approximation for skin chromophore mapping.

The concentrations of blood and melanin in skin can be estimated based on the reflectance of light. Many models for this estimation have been built, such as Monte Carlo simulation, diffusion models, and the differential modified Beer-Lambert law. The optimization-based methods are too slow for chromophore mapping of high-resolution spectral images, and the differential modified Beer-Lambert is not often accurate enough. Optimal coefficients for the differential Beer-Lambert model are calculated by differentiating the diffusion model, optimized to the normal skin spectrum. The derivatives are then used in predicting the difference in chromophore concentrations from the difference in absorption spectra. The accuracy of the method is tested both computationally and experimentally using a Monte Carlo multilayer simulation model, and the data are measured from the palm of a hand during an Allen's test, which modulates the blood content of skin. The correlations of the given and predicted blood, melanin, and oxygen saturation levels are correspondingly r = 0.94, r = 0.99, and r = 0.73. The prediction of the concentrations for all pixels in a 1-megapixel image would take ∼ 20 min, which is orders of magnitude faster than the methods based on optimization during the prediction.

How to assess scar hypertrophy--a comparison of subjective scales and Spectrocutometry: a new objective method.

Scar hypertrophy is a significant clinical problem involving both linear scars from elective surgery and scars caused by trauma or burns. The treatment of hypertrophic scars is often time consuming, and patients may need to be followed up for months or even years. The methods for reliable quantification of scar hypertrophy are at present unsatisfying. We have developed a new, objective method, Spectrocutometry, for documentation and quantification of scar hypertrophy. The instrument is based on standardized digital imaging and spectral modeling and calculates the estimated concentration change of hemoglobin and melanin from the entire scar and also provides standardized images for documentation. Three plastic surgeons have assessed 37 scars from melanoma surgery using Spectrocutometry, the Vancouver scar scale, and the patient and observer scar assessment scale. The intraclass correlation coefficient for the Vancouver scar scale and the patient and observer scar assessment scale was lower than required for reliable assessment (r=0.66 and 0.60, respectively). The intraclass correlation coefficient for Spectrocutometry was high (r=0.89 and 0.88). A Bayesian network analysis revealed a strong dependency between the estimated concentration change of hemoglobin and scar pain. Spectrocutometry is a feasible method for measuring scar hypertrophy. It is shown to be more reliable than subjective rating in assessing linear surgical scars.

Objective scar assessment--a new method using standardized digital imaging and spectral modelling.

INTRODUCTION: Quantitative assessment of scars is needed in clinical practice and in scientific studies. To date, there have been no entirely objective methods available for these purposes. We introduce a new method developed for scar assessment combining standardized digital imaging (SDI) and spectral modelling (SpM). With this method, the estimated concentration changes (ECCs) of haemoglobin and melanin in the scar can be determined quantitatively. PATIENT AND METHODS: In the current study, 22 skin graft donor site (SGDS) wounds were treated with two alternative dressing materials, Suprathel® and Mepilex Transfer®, side by side on the same wound. The SGSD scars were assessed using SDI and SpM. The scars were given subjective ratings by three surgeons using the POSAS and the Vancouver Scar Scale (VSS). The correlations between the ECCs of melanin and haemoglobin and the corresponding subjective ratings were calculated as well as the Intraclass Correlation Coefficient (ICC) of the subjective ratings. RESULTS: There was a statistically significant correlation between the ECCs of melanin and haemoglobin and the subjective ratings. A single observer could reliably assess pigmentation with the POSAS scale (ICC = 0.75) but not vascularity (ICC = 0.51). The reliability ratings of the VSS were unacceptably low. CONCLUSIONS: The ECC values of haemoglobin and melanin give accurate documentation of the scar status. The results also show that the subjective ratings in this study were unreliable especially when interfering pigmentation and increased vascularity were both present at the same time.

The colour of blood in skin: a comparison of Allen's test and photonics simulations.

BACKGROUND: The colour of the skin reflects many physiological and pathological states of an individual. Usually, the skin colour is examined by the bare eye alone. Several scaling systems have been developed to quantify the sensory evaluation of skin colour. In this work, the reflectance of the skin is measured directly using an objective instrument. Haemoglobin inside the dermal circulation is one of the key factors of skin colour and it also has a major role in the appearance of many skin lesions and scars. To quantitatively measure and analyse such conditions, the relation between the skin colour and the haemoglobin concentration in the skin needs to be resolved. METHODS: To examine the effect of blood concentration on the skin colour, five Allen's tests were performed on 20 persons. The skin colour change was measured using a spectrophotometer by changing the blood concentration by the Allen's test. Light interaction with the skin was simulated with a Monte Carlo model, tuning the blood concentration parameter until the simulated and the measured spectra matched, yielding the relationship between the skin colour and the blood concentration. RESULTS: The simulation produced spectra similar to those measured. The change in the blood concentration in the simulation model and in the skin produced changes similar to the spectra. The reflectance of the skin was found to be a nonlinear function of the blood concentration. CONCLUSION: The relationship found between skin colour and blood concentration makes it possible to quantify those skin conditions expressed by blood volume better than plain colour.

Lower extremity ulcer image segmentation of visual and near-infrared imagery.

BACKGROUND/PURPOSE: We propose an automatic ulcer segmentation system with a simple manual correction possibility. In addition to visual color information, we use near-infrared (NIR) images because NIR can penetrate deeper into tissue than visual light. The system is able to measure the surface area of a lower extremity ulcer segmented at its different stages and constructs corresponding healing curves over time. This knowledge is useful in monitoring lower extremity ulcers and helps clinicians select the most efficient therapy. METHODS: Eighteen lower extremity ulcers and one ulcer on the back were examined from 17 patients. The patients were elderly individuals residing in the long-term care department of the Vaasa city hospital. One of the patients (P14) had been diagnosed with diabetes. The inclusion criteria for patients were an ulcer with a suitable size for the imaging device and the free will to volunteer. We developed a four-band spectral digital camera to image the reflectance of the skin. We use the spectral image pixels, in visual light and NIR, in analysis of lower extremity ulcers. For segmentation, the support vector classifier was found to be the best one. The segmentation system is designed to analyze three main ulcer tissue classes: black/necrotic, yellow/fibrous and red/granulation tissue. RESULTS: The experiments conducted confirm the feasibility of our approach. In most cases, the computed healing curves correspond to those made manually. The maximum error rate of ulcer area measurement for red/granulation tissue is 33% for 20 cases. This corresponds to the results published in the literature. The black/necrotic tissue may be located deeper under the skin surface; hence, the ulcer boundaries are not well defined, allowing only a rough estimate, yielding a maximum error of 44% for the three cases analyzed. For yellow/fibrous tissue, we had only one image in our database, whose error value is 23%. CONCLUSION: We propose a new imaging system for segmentation and measurement of different kinds of ulcers. This system is useful in practice for analysis and measurement of ulcer surface areas and observation of their change over time, which helps clinicians in the treatment of ulcers.