The Role of Thermography in Detecting Source of Pain

Millions of people all over the world suffer from the agonies of chronic pain which is perhaps the single most frequent complaint heard in clinics and hospitals. And millions of tablets are sold across the counters in drug stores in every country bringing relief to those who suffer from rheumatoid arthritis, migraine, sciatica, gout and even cancer. But many people experience severe pain for which no apparent cause is known. Conventional methods such as X-rays or other medical tests do not exactly throw any light on the problem and doctors have to resort to an effective diagnostic technique known as thermography

About 2400 years ago when the famous Greek physician Hippocrates painted the bodies of some of his patients with a type of thin liquid cement consisting of wet clay, he noticed that the clay dried faster on warmer parts of the body producing a pattern indicating variations in skin temperature. Hippocrates was not able to explain the reason for these variations, but he came to the conclusion that if one side of the body or one arm or hip was warmer or colder than the other, it meant that there was something wrong somewhere. That reasoning has formed the basis of thermography.

 It is known that as a medical tool thermography was first used about fifty years ago in conjunction with X-rays for locating tumours in the breast. Many doctors in various parts or the United States and several pain centres now employ special thermographic infrared cameras which are connected to a video screen and Polaroid cameras to take thermograms that enable doctors to confirm the presence of pain in patients. Some physicians report a 97 per cent correlation between thermograph findings and traditional diagnostic tests; others humorously describe the thermographic machine as a sort of” lie detector” for pain. Thermograms are now being accepted as evidence by courts in an increasing number of cases involving personal injury lawsuits and workmen’s compensation claims.

A few years ago a 29-year old dental technician suffered due to an unbearable pain following a car accident. She could not even lift her left arm. Even though she presented X-rays and electro­myographic or muscle test readings as proof of her injuries, insurance companies rejected the evidence as inconclusive arguing that the pain might have apparently originated from a latent childhood injury, which could not be located . However, a physician subsequently testified using photographs that visually displayed like a brilliantly colour coded topographical map regions of different skin temperatures on the injured arm. The pictures showed that there was relatively lower blood circulation in some of the areas where the patient was complaining of pain. In the light of other evidence, the photographs were found convincing. She was awarded 50,000 US dollars.

Similarly a bus driver who had suffered lower back injuries was denied disability payment as medical examination did not reveal any organic disorder. Again multicoloured pictures revealed areas of lower skin temperature in the man’s back, thigh and calf indicating a reduced flow of blood in the areas where he said he felt pain. The evidence enabled the patient to win the case. In yet another case a 35-year old woman had been complaining of constant pain after having suffered a neck injury, but doctors were unable to find any physical or organic basis for her pain. Here also a set of brightly coloured pictures indicated an area of relatively cool skin on the left side of her upper chest, confirming a nerve injury in her neck. The evidence was accepted and she was given appropriate medical treatment.

It is known that inflammation caused by infection increases blood flow and heat in an internal organ. The heat can be picked up by the thermograph from the surface of the skin. Thus, an inflamed appendix can give rise to elevated temperature on a particular area of the skin. Temperature variations in certain areas of the skin can be caused by diseases of the veins and arteries nearby that cause clotting, dilation and narrowing of the vessels. Hippocrates himself had found out long ago that it is not the absolute temperature but the difference in temperature that was relevant in indicating that something was wrong. Hence, thermographers do not concern themselves with ‘normal temperature’; they are inclined to view the surface of the body as a weather map, crowded with several thermobars (lines of equal temperature) from cold summits and ridges to warm caves and valleys. When these variations are significantly asymmetrical it usually means that the patient has a problem.

The reason why thermographs reveal painful conditions has not been clearly understood. A damaged disc in the lower spine often shows upon a thermograph as a warm spot on the back, but the actual pain due to the injury may be felt in some other area of the body, such as the thigh or the calf. The pain is thus usually reflected in lower temperatures of skin adjacent to those areas. Some physicians are of the view that a disc injury perhaps irritates sympathetic nerves that control the constriction of small blood vessels resulting in decreased blood flow and lower skin temperatures.

In any case, irrespective of the cause, thermograms appear to be fairly reliable indicators of pain. The thermogram is regarded as a picture of physiology in the same way that an X-ray is regarded as a picture of anatomy. While the X-ray can pinpoint with 99 per cent accuracy the location of broken bones, it is much less dependable if one is looking for evidence of pain caused by nerve damage or muscle spasm. This is where a thermograph is useful because it is more sensitive and can help physicians to evaluate these conditions and may even unearth evidence of a latent injury that the patient is not aware of!

For a thermogram to be taken, special thermographic infrared cameras similar to the ones used by the military in taking night­time pictures of enemy armament installations and troop movements are used. The thermograpic infrared camera can be set to feel the temperature variations of less than two tenths of a degree Fahrenheit at a range of several feet. Its sensitivity is so great that changes in temperature of a patient’s lips and nostrils as he inhales and exhales can be detected and displayed on a video screen as changes in colours. The thermogram must be made in a draft-free room at a temperature between 68° and 72° F. A patient is not permitted to smoke or drink prior to the test because alcohol and tobacco affect circulation. Patients are also required to take rest for about twenty minutes at room temperatures wearing only hospital gowns before a thermogram is taken

• One disadvantage with thermograph is its vulnerability to abuse. There is possibility of the images to be manipulated just as the colours on a TV set. Some unscrupulous operators have even succeeded in setting up ‘thermography mills’ for turning out fraudulent evidence, after learning that thermograms were being accepted as evidence in courts. This in turn has made legitimate thermographers propose standardized examination of techniques and a code of ethics.

Notwithstanding the possibility of abuse, thermographs remain a useful diagnostic tool for confirming pain. Before the advent of thermographs people experiencing pain, but whose X-rays or medical test reports did not reveal anything abnormal, had not been able to counter the argument of defence attorneys or suspicious insurance companies or even their own family physicians. For the first time in medical history such people are able to show convinc­ing evidence of pain with the help of the colourful patterns of a thermogram.