Clinical applications for thermography

Thirty years of clinical use and more than 8,000 peer-reviewed studies in medical literature have established thermography as a safe and effective means to examine the human body. It is non-invasive and, as such, does not require the use of radiation or other potentially harmful elements. Since the world’s first, commercial infrared scanning camera was introduced by Agema in 1965 (a company that subsequently became FLIR Systems), the application scope of this technology has grown exponentially with its falling cost and the medical field has become one of its major beneficiaries. The technology has proven to be a useful tool in research, as well as being helpful in the diagnosis of breast cancer, nervous system disorders, metabolic disorders, neck and back problems, pain syndromes, arthritis, vascular disorders, and soft tissue injuries, among others.

Small nerve fibre dysfunction

One of the latest applications of thermography includes research into small nerve fibre dysfunction using a high end scientific thermal imaging camera. While standard neurological examination and electromyography (EMG) is ideal for looking at large nerve fibres, no noninvasive technique currently exists to detect and qualify small fibre dysfunction that is common in diabetics. In research funded by the Dutch Technology Foundation (STW), thermal imaging technology is now being used for this purpose. The current method of detecting small nerve fibre dysfunction is skin biopsy but this method has serious limitations, explained Dr IR Sjoerd Niehof, thermography expert at the Erasmus University Medical Centre in Rotterdam. “It is an invasive method that involves anaesthesia and is relatively slow. Furthermore, it only reveals information about the small area of skin that has been removed. Our aim was to prove that thermal imaging is a better method allowing us to speed up assessment, saving time and money, while imposing minimal stress on the patient.” The theory behind this method, is based on changes in blood flow. The body’s thermoregulatory control system responds to thermal stimuli by increasing or decreasing local blood flow and this can be detected using thermal imaging technology. For the pilot study, the thermal stimulus was delivered to the patient using a cold plate. Although this proved the concept, the method was uncomfortable for the patient, so the plate was substituted by an infrared lamp. This also provided the benefit of infrared radiation in a specific spectral frequency so a spectral band filter could be used to block that part of the infrared spectrum before it reached the camera. In this way the research team could be certain the measured skin temperatures were accurate. The hypothesis is that the way the body responds to thermal stimuli can indicate the function and integrity of small nerve fibres. If these are compromised the reaction of the body’s control mechanism is likely to be altered. Indeed, early tests have shown that patients with small nerve fibre dysfunction show a slower response to the thermal stimulus than healthy individuals. In some cases, those with the condition have shown no response at all. The thermal imaging camera used for this work is a FLIR Systems SC5000 which is specifically designed for scientific applications. Its InSb focal plane array provides thermal images of 640 x 512 pixels at a sensitivity rating below 20 mK (0.02°C) Although the primary focus of this work is on small nerve fibre dysfunction Dr Niehof confirmed the research has wider scope: “We want the system to be used for other diseases as well. For example, we think it would be helpful for burn injuries, Raynauld’s disease, and vascularisation of skin cancer to name but a few.” He continued: “The use of thermal imaging technology in medicine is currently limited by the absence of standardisation in recording methods and lack of knowledge of the underlying mechanisms that result in the measured temperature differences. With this research we hope to partially fill those gaps.”