A heat transfer model of skin tissue for the detection of lesions: sensitivity analysis.

Cetingül MP¹, Herman C.

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Abstract

In this paper, we study the transient thermal response of skin layers to determine to which extent the surface temperature distribution reflects the properties of subsurface structures, such as benign or malignant lesions. Specifically, we conduct a detailed sensitivity analysis to interpret the changes in the surface temperature distribution as a function of variations in thermophysical properties, blood perfusion rate, metabolic heat generation and thicknesses of skin layers, using a multilayer computational model. These properties can vary from individual to individual or depend on location, external and internal influences, and in certain situations accurate property data are not available in the literature. Therefore, the uncertainties in these data could potentially affect the accuracy of the interpretation/diagnosis of a lesion in a clinical setting. In this study, relevant parameters were varied within characteristic physiological ranges, and differences in the surface temperature response were quantified. It was observed that variations in these parameters have a small influence on the surface temperature distribution. Analysis using this multilayer model was further conducted to determine the sensitivity of transient thermal response to different lesion sizes. This work validates the idea of examining the transient thermal response obtained using a thermal imaging system with the objective of lesion identification. The modeling effort and the sensitivity analysis reported in this paper comprise a portion of a comprehensive research effort involving experimentation on a skin phantom model as well as measurements on patients in a clinical setting, that are currently underway. One of the preliminary results from the ongoing clinical trial is also included to demonstrate the feasibility of the proposed approach.

Heat transfer model for deep tissue injury: a step towards an early thermographic diagnostic capability

Akanksha Bhargava,¹ Arjun Chanmugam,² and Cila Herman¹

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Abstract

Background

Deep tissue injury (DTI) is a class of serious lesions which develop in the deep tissue layers as a result of sustained tissue loading or pressure-induced ischemic injury. DTI lesions often do not become visible on the skin surface until the injury reaches an advanced stage, making their early detection a challenging task.

Theory

Early diagnosis leading to early treatment mitigates the progression of the lesion and remains one of the priorities in clinical care. The aim of the study is to relate changes in tissue temperature with key physiological changes occurring at the tissue level to develop criteria for the detection of incipient DTIs.

Method

Skin surface temperature distributions of the damaged tissue were analyzed using a multilayer tissue model. Thermal response of the skin surface to a cooling stress, was computed for deep tissue inflammation and deep tissue ischemia, and then compared with computed skin temperature of healthy tissue.

Results

For a deep lesion situated in muscle and fat layers, measurable skin temperature differences were observed within the first five minutes of thermal recovery period including temperature increases between 0.25°C to 0.9°C during inflammation and temperature decreases between −0.2°C to −0.5°C during ischemia.

Conclusions

The computational thermal models can explain previously published thermographic findings related to DTIs and pressure ulcers. It is concluded that infrared thermography can be used as an objective, non-invasive and quantitative means of early DTI diagnosis.

Medical Infrared Imaging

Skin temperature measured by infrared thermography after ultrasound-guided blockade of the sciatic nerve.

van Haren FG¹, Kadic L, Driessen JJ.

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Abstract

BACKGROUND:

In the present study, we assessed the relationship between subgluteal sciatic nerve blocking and skin temperature by infrared thermography in the lower extremity. We hypothesized that blocking the sciatic nerve will lead to an increase in temperature, and that this will correlate with existing sensory block tests.

METHODS:

We studied 18 healthy individuals undergoing orthopaedic surgery of the foot under ultrasound-guided subgluteal blockade of the sciatic nerve with 30 ml ropivacaine 7.5 mg/ml. Skin temperature was measured on the toes, the dorsal and plantar side of the foot, the malleoli, and the lateral side of the lower leg, just before sciatic nerve blockade and at 10-min intervals thereafter.

RESULTS:

Baseline skin temperatures showed a significant distal-to-proximal gradient. After sciatic block, temperatures on the blocked side increased significantly in the toes and foot. When comparing pinprick to skin temperature in a receiver operating curve, there was an AUC of 85.9% (95% confidence interval = 83.7-88.2%, P < 0.001). The medial malleolus (not being innervated by the sciatic nerve) showed no significant difference to the lateral.

CONCLUSIONS:

After sciatic nerve block, temperatures of the foot increased significantly. There was a good correlation between pinprick testing and infrared temperature measurement. This makes infrared skin temperature measuring a good test in determining block success when sensory testing is impossible.

© 2013 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Medical Infrared Imaging

Does the temperature gradient correlate with the photodynamic diagnosis parameter numerical colour value (NCV)?

Cholewka A, Stanek A, Kwiatek S, Sieroń A, Drzazga Z.

Source

Institute of Physics, Department of Medical Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland. armand.cholewka@gmail.com

Abstract

BACKGROUND:

Photodynamic diagnosis (PDD) as well as thermovision belong to the category of non-invasive optical diagnosis techniques. Among many different skin cancer diseases, basal cell carcinoma (BCC) is the most frequently occurring one (almost 95% of all skin tumours). In contrast, seborrhoeic keratosis represents almost 70% of benign skin tumours. In this paper we present infrared thermography as an additional method, combined with PDD, to show the differentiation between these two skin mutations.

METHODS:

The photodynamic diagnosis studies were performed by using the autofluorescence diagnosis system Xillix Onco. As an additional non-invasive diagnosis technique, thermovision studies were performed. Thermal imaging was done by using a Thermovision Camera A40M with a sensitivity of 0.07K. The thermograms of the chosen areas were performed in a special room with a temperature of 22.5±1°C. All patients were treated in the Chair and Clinic of Internal Diseases, Angiology and Physical Medicine in Bytom. Thirteen skin lesions were studied: 9 diagnosed as basal cell carcinoma and 4 as seborrhoeic keratosis. All skin lesions were confirmed in histopathological examinations.

RESULTS AND CONCLUSIONS:

The results of the studies revealed significant differences in skin thermal mapping between patients suffering from basal cell carcinoma and seborrhoeic keratosis. It appears that benign skin lesions are characterised by a lower mean temperature than the surrounding healthy skin. To the contrary, cancerous skin mutations appeared on the thermal map at a higher mean temperature. Thermal images for the chosen skin lesions and temperature parameters derived from the thermograms are contiguous with the photodynamic diagnosis results and may give some additional diagnostic information.