Thursday, March 20, 2008

Thermal imaging – a hotspot for the future?

Thermal Imaging has been considered for use in a wide range of medical circumstances. It has been shown to be useful in aiding diagnosis and guiding management of foot injuries in military recruits when combined with clinical examination, radiographs and bone scanning.4 Telethermography has been demonstrated as a useful tool in aiding diagnosis and management of sports injuries.5 Cole et al. demonstrated a significant relationship between early thermographic assessment of the depth of skin burns and clinical outcome.3 Various types of thermal imaging have also been used in studies of diabetic neuropathic feet,1 the detection of carpal tunnel syndrome,7 the investigation of tendon injuries in horses6 and in the monitoring of undesirable thermal proximity damage during surgical energized dissection and coagulation.2 During the international severe acute respiratory syndrome (SARS) crisis of 2003, thermal imaging was employed as a screening tool at border points. At Singapore's Changi International airport alone 442,973 passengers were screened and of those 136 identified for further investigation and observation.8 The modality's sensitivity for identifying passengers with even low grade pyrexia (>37.5 °C) highlights recent technological advances and brings to attention future possible uses.

The main problems previously identified with the use of thermal imaging in the evaluation of a possibly injured limb include a lack of specificity in identifying the site and nature of pathology and difficulty in establishing normal references. While thermography could never replace radiography as a diagnostic tool, it may be useful as an adjunct to clinical examination and X-ray. As this case demonstrates, children can prove difficult to assess in the accident and emergency department environment. Injury localisation in this patient group can prove difficult and the “survey” of a limb with X-ray may result. The use of thermal imaging could improve the sensitivity of clinical examination and therefore assist in injury localisation, preventing unnecessary X-ray exposure.

In this case it may be postulated that thermal imaging has detected a localised increase in temperature associated with the normal inflammatory response to a fracture. This is an early response and if it was shown to be reliable then the modality may be useful in a wider area of emergency medicine. Early radiological findings can be unreliable in conditions such as scaphoid fracture and the “toddler's” type fracture of the tibial shaft. Thermal imaging could potentially be used in early follow-up to exclude fracture in these situations and prevent prolonged immobilisation and possibly more invasive and expensive bone scanning. It is likely that thermal imaging would be of use when examining bones that are relatively superficial where temperature changes are going to be more apparent.

Thermal imaging has been shown to be effective in assessing the depth of skin burns3 by measuring different skin temperatures created by varying states of perfusion. It may therefore be useful as a real time assessment tool examining changes in peripheral perfusion during the resuscitation of a shocked patient, giving a continuous recording of response to treatment.

Modern thermal imaging is rapid, non-invasive, non-emitting and with improving technology becoming more user-friendly and more cost effective. Given these attributes and the potential applications to emergency medicine outlined above, there is a need for our speciality to study the technique further.

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