Petri Välisuo

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.

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.

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.

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.

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.

Solving Optical Skin Simulation Model Parameters Using Genetic Algorithm

Near infrared spectroscopy is noninvasive method to obtain information from materials, such as human skin. A simulation model of light interaction with skin is used to simulate skin reflectance spectra when the chemical and physical parameters of the skin are known. Genetic algorithm is utilised for tuning the simulator to solve the inverse problem; to calculate the skin parameters from the measured reflectance spectra. The inverse problems are often ill-posed, which was also true for this problem in its original form. After assuming all physical parameters as fixed, the problem was regularised and a unique solution for blood melanin and water concentrations was found in all simulations. The accuracy and the uniqueness of the solution proved to be almost independent of the provided spectral resolution, as long as it is larger than three wavelengths. The accuracy of the solution depends on the MCML simulation noise level and the fitness function used. The performance of four different fitness functions was evaluated using fitness landscape and noise analysis, and the best of them was chosen. The achieved accuracy is satisfactory for many applications and it can probably be further improved by increasing the number of photons used in the MCML simulation or by further optimising the fitness function. Index Terms—Genetic algorithms, Monte Carlo methods, In- verse problems, Biomedical engineering, Optics, Biological tis- sues.

The Effect of the Shape and Location of the Light Source in Diffuse Reflectance Measurements

Optical measurements are fast and convenient mode to obtain information from human skin. However, the complicated interactions of light with skin may overwhelm our understanding of the measurements. Moreover, the high remittance from the surface of the skin may be often an obstacle for making measurements regarding deeper layers of skin. In this research, we have constructed a simulation model to show from which depths the remittance is coming from. Using this model we have studied the effects of light source shape and location to measure the remittance originating deeper. According to the model, the ring-shaped light source more than doubles the measurement depth, compared with the diffuse light. In fiber-based measurements, increase of the fiber separation increases the measurement depth.

Near infrared wavelength relevance detection of ultraviolet radiation-induced erythema

The acute effects of sun-bathing on the near-infrared absorption spectra of human skin were studied by exposing the shoulders of a male test subject to bright Finnish high summer mid-day sun. The spectra were measured before, immediately after and for several days after exposure. Four different spectral processing and classification methods were applied to the data set to identify differences caused by exposure to the sun. The spectrophotometer and measuring procedure were found to cause some systematic errors, calling for further development, even though they could, to a large extent, be compensated for computationally. Spectral regions indicating ultraviolet radiation-induced erythema were located and the degree of erythema could be predicted correctly but the signal is weak. This paper discusses promising wavelength selection methods to study the dermal effects of exposure to the sun, as well as difficulties and remedies of near infrared spectroscopic measurements of the skin.

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.

Long-Term Results of Intralesional Triamcinolone Acetonide Injections inKeloid Treatment

Background: Intralesional triamcinolone acetonide (TAC) injections are often used as the first alternative for treating keloid scarring. The long-term outcome of this treatment is unclear. Also, undesirable local side effects have been recognized in clinical work and literature but they have been labelled as harmless and rare. Methods: We documented the long-term outcome of intralesional TAC injections in the treatment of keloid scars in Tampere University Hospital. The main objectives were to investigate the remission rate and the occurrence of local side effects. We assessed 105 patients (46 women, 59 men) with 138 TAC treated keloid scars at the outpatient clinic. The keloids were photographed and assessed with Patient and Observer Scar Assessment Scale (POSAS). Results: Of the 138 keloids, 90 (65%) were clinically in remission. Local side effects, including atrophy of the skin or the subdermal fat, telangiectasia and cortisone traces, occurred in 55% of the cases. The number of injections did not correlate with remission rate or the occurrence of local side effect. ROC curve analysis showed that surface area >620 mm2 was a prognostic factor for not responding to TAC treatment. Conclusion: According to this study, intralesional TAC injections seem to be effective in the treatment of small keloids but not in larger than 620 mm2. Local side effects were more frequent than previously reported and occurred even after just 1 injection. The side effects seem to be permanent in nature.