Dynamic Thermography

Infrared thermography or infrared thermal imaging is based on analysis of skin surface temperatures as a reflection of normal or abnormal human physiology using a highly specialized IR-camera. In a fraction of a second, a large area of the human body can be imaged to an accuracy of less than 0.1°C as well as a spatial resolution of 25-50 micrometers (6) and, dynamic responses to stimuli are easily documented (1, 2). There are many circumstances where skin surface temperature and infrared emission are proportional to local blood flow.

Skin circulation can also be examined dynamically using IR-thermography. The technique of dynamic infrared thermography (DIRT) is based on the relationship between dermal perfusion and the rate of change of skin surface temperature following the application of a transient local thermal challenges (3,4, 5).  -  see also the 3 video examples below.

With dynamic infrared thermography it is possible to better evaluate skin perfusion.  It is very difficult to obtain adequate information on the dynamics of perfusion physiology with static infrared thermography. Rapid physiological changes can be readily registered with the new generation of infrared cameras. The information can be easily analysed using infrared camera which employ, for example, fire-wire technology. This new development allows real time analysis of images (i.e. image sequencing rather than just still pictures).  Having access to this technology provides an enormous advantage in the use of IR-thermography. This is especially important since being able to follow dynamic changes in skin temperature opens up a whole new field of possibilities for this technique. For example, it is very usual to use provocation tests (responses to heating and cooling) in both research and clinical situations.

1. Ohashi, Y. & Uchida, I. (2000). Applying dynamic thermography in the diagnosis of breast cancer.  IEE Enginer. Med. Biol. 19: 42-51.

2.  Rasmussen, L.K. Nielsen Johannsen, B. and Mercer, J.B. (2001). Changes in skin temperature in the hands and feet of young and elderly subjects in response to local cooling. Proceedings of the  Australian Physiological and Pharmacological Society. Suppl. 1. Vol. 32, No. 2. 126P.

3. Francis JE, Roggli R, Love TJ. Thermography as a means of blood perfusion measurements. J Biomech Eng 1979;101: 246-249

4. Wilson SB, Spence VA. Dynamic thermographic imaging method for quantifying dermal perfusion: potential and limitations. Med Biol Eng Comput 1989;27:496-501

5. Boe Setså, L., Mercer, J.B., de Weerd, L. & Elveness, O.P. (2005). Dynamic Thermography as a reliable, non-invasive and easy method for monitoring perfusion in free flap surgery, preliminary results. Thermology International 15: 75.
High speed video sequence showing  the effect of a mild fan cooling of the dorsal surface of the hands. The fan cooling period lasted 2 minutes. Note how the arteriovenous anastomosis in the finger tips open up at the end og the cooling period and how the hand rewarms "backwards" from the finger tips
Rewarming of hands in a patient with Raynauds syndrome. Prior to the rewarming the hands were placed in cold water for 1 minute. Note the asymetric warming pattern followed by a hyperaemic response.
In this sequence the finger tips were placed in ice water. Note how the superficial venous drainage becomes visible due to the venous blood being cooled. At first the veins are quite evident but with time the picture becomes more diffuse as the temperature of the tissue in close proximity to the veins also starts to cool down
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