Thermal imaging – a hotspot for the future?

Case report

A 6-year-old boy presented to accident and emergency with his mother complaining of a painful right elbow following a fall that day. He fell whilst walking up steps and gave a history of directly striking the elbow on the step. He had not been using the arm since. There was a recent history of a comminuted intra-articular fracture of the proximal ulna of the same elbow, and a cast had been removed just 5 weeks previously.

The patient was seen and examined by an experienced A&E senior house officer. He was difficult to assess and was complaining of pain in the entire arm. There was no swelling or deformity and no apparent bony tenderness to the limb. He was unwilling to actively move the elbow joint, however there was a good range of passive movement throughout the arm and good grip strength was noted. An X-ray of the elbow was performed and no bony injury or effusion of the elbow joint was apparent. The child was treated for a soft tissue injury of the elbow, advised regular analgesia and discharged.

The patient represented two days later complaining of persistent pain to the arm. He was now localising pain to the wrist and there was a corresponding area of tenderness over the distal radius. A thermal image was taken of the limb using a hand held FTI Mv thermal imager interfacing with LIPS Mini PC software. The image identified an obvious “hotspot” corresponding to the area of tenderness over the distal radius (Fig. 1 ), which clearly differed from a thermal image of the normal wrist (Fig. 2 ). Subsequent X-ray of the wrist revealed an undisplaced greenstick fracture of the distal radius. The child was treated with a plaster cast, referred to the orthopaedic fracture clinic and made an uneventful recovery.

Figure 1.

Thermal image of injured wrist with hotspot localising greenstick fracture of the distal radius.

Figure 2.

Thermal image of normal wrist.

Discussion

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.