The method of thermography (also thermography) is used to measure the body surface temperature, which is directly related to the local metabolism (metabolism) of different tissues. Body heat is emitted through the skin in the form of electromagnetic radiation, which is collected and processed by special detectors, such as an infrared-sensitive sensor. Pathological (disease-related) processes can be manifested by an altered surface temperature and thus diagnosed. Increased metabolism with increased heat generation, for example, can be a sign of inflammation. Thermography was first used by R. N. Lawson in 1956 in breast carcinoma diagnostics (breast cancer diagnostics).
Indications (areas of application)
- Osteoarthritis (joint wear and tear)
- Polyarthritis (inflammation of multiple joints)
- Epicondylitis humeri radialis (tennis elbow) or epicondylitis humeri ulnaris (golf elbow).
- Dysfunction of the spine
- Rheumatic inflammatory foci
- Acute deep vein thrombosis (TBVT) – occlusion of a deep leg vein by a blood clot.
- Peripheral circulatory disorders (eg, in the hands or feet in diabetes mellitus).
- Peripheral arterial occlusive disease (pAVK).
- CRPS (chronic regional pain syndrome, Sudeck’s syndrome) – persistent pain after an injury (for example, after a distal radius fracture – fracture of the radius) caused by a disorder of the autonomic nervous system.
- Raynaud’s syndrome – vascular disease caused by vasospasm (vascular spasm). The result is a temporary lack of blood flow to the fingers, for example.
- Changes in the testicle such as a varicocele (varicose vein hernia).
- Suspicion of mammary carcinoma* (breast cancer).
- Follow-up of physical therapy series
* Note: U.S. Food and Drug Administration (FDA) indicates that infrared thermography is approved in breast cancer diagnosis only as an additional diagnostic method and not as a replacement for mammography screening.
The procedure
The skin temperature is approximately 5 °C below body temperature. The level of skin temperature is determined by the vascular supply, the degree of blood flow to the skin (venous blood flow), and the metabolism of the underlying tissue. The basis for the evaluation of thermography is the assumption that in a healthy subject the heat distribution of both sides of the body is symmetrical. The patient’s thermograms are compared with the results of an extensive measurement of a total of 40 body regions (both right and left halves of the body) of healthy test subjects. Differences of up to 0.2 C° are already perceptible, a deviation of 1 °C between corresponding body surfaces is significant and is considered to be pathological for sure. There are several thermographic methods:
- Liquid crystal thermography: this is contact thermography (or plate thermography, if appropriate) in which the body part to be examined is placed on a film impregnated with cholesterol esters. The cholesterol esters are optically active and change color within a defined temperature range. This change is recorded via special sensors.
- Infrared thermography: an infrared camera records computer-aided very accurate thermograms. The procedure covers a wide area and can be performed without direct contact.
- Cold-induced stress thermography: the tissue is cooled by a cooling stimulus (e.g., immersing the hands in cold water). Subsequently, the regulatory rewarming of the tissue is recorded by an infrared camera. This thermoregulation can provide information about pathological processes.
For a thermogram to give reproducible measurement results, the following measurement conditions are required:
- Standardized, uniform room temperature (approx. 20-24 °C).
- Humidity of 45-60
- Defined initial thermal situation (no heat or cold exposure of the patient by, for example, physical exertion).
- No consumption of nicotine, alcohol, coffee and tea.
- Lateral symmetrical measurement (comparative measurement of both halves of the body).
Thermography is a useful procedure both for the diagnosis of inflammatory diseases of the musculoskeletal system and for complementary tumor diagnosis.
