By: Akshath Rudrachar, Pharmacovigilance Writer
Thermography is one of the non invasive tests, utilizing very sophisticated infra-red cameras and desk top computers. The thermal imaging technicians simply capture a photograph of the part - an infra-red photograph, or heat picture - and the data is stored in a computer and can then either be printed on high resolution color printers, or sent electronically to a physician with a similar computer for analysis.
The radiologist or thermal imaging specialist then compares the heat patterns of the left side and the right side of body. Any difference in heat or any specific blood vessel patterns in one side of the body that does not appear in another side indicate a physiologic abnormality. This may be pathological (a disease) or it might indicate an anatomical variation. When a thermogram is positive, the job of differential diagnosis begins.
Some of the common uses of Thermography are:
Breast pathologies: Like breast cancer, benign tumours, mastitis, and fibrocystic breast disease. The concept is quite simple; it measures the heat coming from body, as metastatic cancers create heat which can be imaged by digital infrared imaging. It also helps to locate tumor size and locates surgical area and monitors the healing process after surgery.
Extra-Cranial Vessel Disease: In a similar way, a variety of conditions which relate to flow of blood through the vessels of the head and neck can also be accessed with thermal imaging. The use of Thermography in differentiating various types of headaches (migraine, cluster, cervical spine related), facial nerve injury, and the visualization of tempero-mandibular joint disorders are commonly used aspects of thermographic diagnosis.
Neuro-Musculo-Skeletal: This is one of the best examples of Thermograph’s ability to accurately diagnose patients with back, neck, and extremity disorders. In fact, it was the use of Thermography by chiropractors, a neurologist and orthopedist in the late 70's to the late 80's in spinal injury cases from car accidents and work injuries, which really launched the clinical interest in this diagnostic tool.
When muscle tissue is strained or torn, it releases chemicals which cause increase in heat. This heat can be seen as intense patterns of hyperthermia in the region of the muscle.
In case of nerve damages like disc herniation and spinal nerve root compression the intense patterns of hypothermic impression can be seen in the thermographic map, just exactly the opposite direction as muscle injury.
Lower Extremity Vessel Disease: The ability of Thermography to detect the presence of deep vein thrombosis and other circulatory disorders of the lower extremities is a very exciting application of this procedure as it allows painless and safe detection of the disease.
Another aspect of thermal imaging is in diagnosis of diabetic neuropathies of the feet. In the Thermography camera the diabetic neuropathy patient’s feet demonstrate 1-2 degrees centigrade colder than the upper part of the leg, and the toes are not visible to the camera as they have become so hypothermic. This can be seen several years before the patient diagnosed with diabetic neuropathy. This can give the patient time to treat the condition before permanent nerve damage occurs to the foot.
Respiratory dysfunctions: Infrared Thermography was applied during the last epidemic of atypical pneumonia (SARS) at airports and is useful for monitoring asthma, allergies, bronchitis, influenza etc.
Skin Problems: Infrared Thermography gives a more precise level of information - skin tumors and skin cancers, and wound healing.
Dentistry: Dentists recommend the use of Medical Thermography in monitoring control in the inflammation process into oral cavity and reaction of the regional lymphatic nodes, maxillary joint disease and other chronic diseases of the bones, nerves, located in the maxilla facial area. It can also measure temperature changes in the application of new methods and dental materials applied by dentists.
Limitations and Disadvantages of Thermography
- Unable to show exact mass size and location for biopsy purpose.
- Verification of “benign” vs. ‘malignant” may be difficult.
- Does not provide exact information regarding the kind of lesions, severity, and structural features of lesion.
- Current technique has a limitation in penetrating the thick skull, chest, abdomen, pelvis, and also bone, only surface of the body can be evaluated.
- If a thermal imaging laboratory or doctor tells that Thermography can see organs, they are gravely mistaken. Thermography is a test of physiology. It does not look at anatomy or structure, and it only reads the infra-red heat radiating from the surface of the body.
- If the patient scratches their body vigorously without the technician seeing this, a heat signature would be produced that would cause the interpreting physician to think there was an infection in the body or a cancer.
Regulatory Action on Breast Thermography
The FDA has sent several warning letters to health care providers and a Thermography manufacturer who claims that digital infared thermal imaging can take the place of mammography.
Thermography devices have been cleared by the FDA for use as an adjunct or additional, tool for detecting breast cancer, which means Thermography should not be used by itself to screen for or to diagnose breast cancer.
There is still a lack of really large published series in many aspects of Thermography in which Thermography has been fully correlated and evaluated with clinical and other diagnostic data. Modem medical thermographic apparatus is still relatively primitive but the likelihood of improved apparatus becoming available is great. The technical knowledge necessary for the production of satisfactory thermograms has already been acquired and is in use in other fields. This technique could be applied to medical needs once the apparatus becomes available.