November 25, 1997
Clinical thermography is the detection and recording of a patient's skin surface thermal patterns, using instruments which can provide visual and quantitative documentation of these temperature measurements.
Thermography is appropriate and germane to health care practice whenever the treating physician feels a physiological imaging test is needed for diagnosis. Thermography is a physiologic imaging technology which provides information on the normal and abnormal functioning of the sensory and sympathetic nervous systems, vascular dysfunction, myofascial trauma and local inflammatory processes.
It may contribute to diagnosis and patient management by assisting in determining the site and degree of irritation, the type of functional disorder, the prognosis of treatment, as well as assisting in the determination of the most effective treatment and case evaluation.
Thermography is an acceptable analytical procedure which may be performed by a licensed doctor or under their direct supervision in cases which demonstrate adequate clinical justification; however, a professional holding appropriate credentials with regard to knowledge, skill and experience in thermography must interpret the result.
Currently there are two recognized methods of thermographic imaging; infrared thermography (IRT) and liquid-crystal thermography (LCT).
Clinic: The temperature of the room should be such that the patient is not perspiring nor shivering. The preferred temperature range is between 18 and 23 degrees C. Room temperature changes during the course of an examination must be gradual, so that all parts of the patient's body can adjust uniformly. The temperature should not vary more than one degree Celsius during the course of a study. The examining room must have an ambient temperature thermometer to monitor the room temperature.
The patient must be placed in an open area, equidistant from walls. The thermographic room should be carpeted. Windows should be covered to prevent excess infrared radiation from entering or escaping from the room. Shades or blinds may be adequate for this purpose. Windows and doors should be adequately sealed to prevent drafts, in the area where the patient is positioned. Heat and air conditioning sources must be minimized in the room, and kept well away from the patient. Vents should be directed away from the patient and should be thoroughly baffled or turned off during examination. Standard fluorescent and diffused incandescent lighting is adequate, with fluorescent lighting preferred.
Patient: The patient should equilibrate with laboratory ambient conditions for sufficient time to approximate a steady state, after which further equilibration results in minimal surface temperature changes. This equilibration period will typically be 15-20 minutes. During the equilibration period, and the subsequent examination, the area to be viewed should remain completely uncovered of clothing, jewelry or gowning. A loose gown may be worn, provided that it does not restrict air flow for equilibration and does not constrict the skin surface in any way which would produce an artifactual result on the thermogram. Special gowning procedures, specific to the clinic or examination, may be required and are permitted, as long as the above stipulations are observed (ie. no restriction of equilibration of areas to be viewed, and no constriction which could produce artifacts in other areas).
The patient should be provided with instructions intended to reduce the likelihood of artifacts or inconclusive thermography. Make-up, vasoactive drugs, and therapy which will produce altered cutaneous blood flow are prohibited or discouraged for appropriate periods prior to the thermographic scan.
Equipment: Contact (liquid-crystal) thermography utilizes a range of interchangeable "screens" or "pillows" impregnated with cholesteric methyl-ester derivatives which change color as a function of their temperature. The thermal precision of the equipment is generally within adequate limits for clinical interpretation.
Non-contact, electronic, telethermography equipment utilizes an infrared detector which scans the field-of-view in two directions simultaneously. Temperature repeatability and precision of 0.1 degree C detection or better is adequate for electronic thermographic equipment. Absolute temperature measurements are generally not required for a clinical diagnostic impression; only relative temperatures and temperature differentials are relevant parameters. Electronic studies should be performed with the scanner perpendicular to the surface to be viewed. If other than perpendicular views are required, the angle must be kept exactly the same for comparable, bilateral views.
When multiple views are required for bilaterally equivalent areas,the equipment settings must not be altered for the two views.
Documentation: Each thermography series should include all, or as many body surfaces as possible which are relevant to the patients complaint and symptomatology, along with anatomically and physiologically related areas. These records (views) should contain as much detail as possible.
Each thermographic image, captured on archival media, should contain an indication of the anatomic view in the image along with the following minimum of information, either included with the original image or immediately traceable to other archived documents:
- patients name or identification code and date
- clinic facility name and address
- name of the doctor
If a patient identification code is used, it must be clearly identifiable on each archival document, whether a single view, a series or the patient records in the clinic files.
Examination protocol: A thermographic series consists of one or more images, captured on archival medium, which permit the evaluation of body surface area relevant to the purpose of the examination. Typically, the entire upper body or lower body is examined to determine vascular, autonomic and neuromuscular involvement of the physiology related to these areas. Specific or limited views may be appropriate in the diagnosis or documentation of a particular lesion or injury.
A single thermographic series is considered adequate, if performed under conditions outlined above, and if the findings are negative with respect to the clinical impression. If the findings are questionable or positive with regard to the clinical impression a second series is recommended to rule out artifacts and confirm the abnormal findings. If the findings from the two studies are not comparable, the study should be considered invalid and a third series should be done, following an extended period for re-equilibration.
Stress studies involving symptom exacerbation, autonomic challenge or alcohol spray may be performed following a first, baseline, thermographic series.