As Published in the Journal Today’s Chiropractic; Vol 23, No 3: 38-41

     The evolution of modern paraspinal thermography (digital infrared imaging) has been driven by the chiropractic professions core principle that both health (homeostasis) and disease are nervous system dependent. Today, as never before, the health sciences are recognizing the need to monitor the nervous system’s function due to its unique role in the maintenance and restoration of health. Gray's Anatomy (1991) states that "Homeostatic responses are innate in all living organisms, but with increasing size and complexity of structure, the range and flexibility of responses has steadily increased in parallel with the evolution of the nervous system ". It further states that "its structure and activities are inseparable from every aspect of life; physical, cultural, and intellectual". There is no longer any doubt within the scientific community that the nervous system is a major, if not the major, contributing factor in the maintenance of health. All of this, combined with health care's new focus on outcome based treatment, has created the need for an objective means to determine the need for care and the effectiveness of the treatment rendered. With the event of modern computerized paraspinal thermography, the field chiropractor now has the means of monitoring nervous system function on a pre and post adjustment basis thus fulfilling the needs of modern outcome based treatment.

     It was very fortunate for our profession that Drs. D.D. and B.J. Palmer had the foresight and wisdom to include both the neurophysiological and biomechanical components into the subluxation complex. Uniquely, it is the neurological component that distinguishes our profession from all other health care disciplines. Yet, our current emphasis has been almost exclusively on aberrant spinal biomechanics (leg length deficiencies, postural imbalances, weakened muscles, and aberrant joint motion to name a few). We often claim that we can affect the neurology of the body by restoring normal spinal biomechanics (adjustment), but until now the technology has not been available to objectively quantify neurophysiological changes on a pre and post adjustment basis.

     The initial attempt to quantify nervous system function was undertaken by Dr. B.J Palmer in the early 1920's. He was responding to the claim by some practitioners that they could detect "hot spots" over the spine with the palm or back of their hands. These "hot spots" were thought to be caused when a subluxated vertebra "causes pressure upon the surrounding tissues of a nerve or bundle of nerves and this causes resistance to the flow of nerve energy. This resistance in turn causes excess heat (hot spots) at that point".

     In 1923, Dr. Palmer enlisted the assistance of Dr. Dossa Evins to research and design an instrument that would be able to measure these areas of excess heat. Dr. Evins' research lead to the development of the Neurocalometer (NCM) which was based on the thermoelectric principle discovered by the German physicist, T.J. Seebeck in the 1820's. Seebeck had discovered that an electrical current flows in a circuit made up of two dissimilar metallic conductors (thermocouples) when the temperature of their two junctions are different. The NCM was a hand held, bi-probed thermocouple instrument that measured comparative or relative (right to left) skin temperatures on a horizontal plane. With its terminals straddling the spinous processes, the instrument was firmly glided over the spine. Dr. Palmer claimed that when the instrument passed over a point where a nerve was impinged, the "excess heat" produced by the subluxation would "cause the needle to deflect in a certain characteristic way (pattern), showing so many points on its meter". Further, he claimed that the instrument could locate that exact point where the nerve pressure existed. Of course, even if the nerve could possibly emit heat due to compression alone, to locate the exact point would require an instrument that could isolate this "excess heat" through inches of dermis, adipose, muscles, tendons, ligaments, and flowing blood. An impossible feat by any standard as the surrounding tissues and flowing blood would certainly dissipate this low level of heat emission before it reached the skin. What he had actually done, however, was to invent one of the first instruments to measure skin temperature differentials (thermometry).

     Although his interpretation of what he though he was doing was incorrect, his discovery of using paraspinal skin temperature differentials to monitor the nervous system was quite significant. Today, physiologists such a Guyton inform us that the temperature of the skin is under the direct control of the sympathetic nervous system which regulates the quantity (volume) of blood flowing through the dermis via vascular contraction and dilation. In an actual sense then, we can monitor the real-time neurophysiology of the body via the thermodynamics of the dermis.

     The discovery of the NCM represented a major contribution to the evolution of the chiropractic practice. At last there was a method to "objectively" (though crudely by today's standards) monitor the effects that the subluxation, and the adjustment, had on the neurophysiology of the body. However, the NCM's use presented a significant obstacle in that it was too dependent upon the memory and interpretive skills of the doctor. The doctor not only had to use extreme care in gliding the instrument over the spine, but also simultaneously memorize every deflection of its needle and the exact location of each deflection. At the conclusion of the scan, the doctor would have to transcribe from memory onto recording sheets all the needle deflections and their locations. It can be easily seen that this information, which was so critical to the care of the patient (the primary indicator for the adjustment), could be erroneously recorded. This lead to the development of the Neurocalograph (NCGH) by Otto Schiernbeck. The NCGH was essentially an NCM hooked up to a recording device that would automatically produce a hard copy readout of all the thermal shifts, totally eliminating the need for memorization and transcription. The NCGH, using vacuum tube technology, was a major technological advancement over the NCM, and was chiefly responsible for establishing the thermal pattern (thermography) as an indicator for the subluxation.

     The success of the NCM/NCGH soon spawned the development of other instruments using similar technology. Three of the most noteworthy were the Nervoscope/Analograph introduced in the late 1940's, Thermeter/Thermoscribe introduced in the 1950's, and the Syncrotherm which appeared in the 1970's. Both the Analograph and the Thermoscribe were, and still are, thermocouple instruments. The Syncrotherm differed in that it used thermistors (highly sensitive thermocouples) and simultaneously recorded direct separate channel readings of both the right and left sides of the spine onto hard copy readouts. Research on the Syncrotherm was terminated by Canadian Memorial Chiropractic College in the 1970's, while production of the Analograph and Thermoscribe continues today.

     Although these thermocouple instruments represent major efforts to quantify and monitor nervous system function, the outdated technology used in these instruments present many significant limitations. The most crucial problem encountered involves the thermodynamics of the thermocouples themselves. When the metallic thermocouple probes are placed on the skin the colder wires quickly warm toward the temperature of the skin while the skin's temperature is cooled toward the temperature of the metal thermocouples, thus changing the actual skin temperature attempting to be read via conduction (adhering to the Zeroth Law of Thermodynamics). Some doctors attempt to overcome this problem by "seasoning" or acclimating the probes to the patient by allowing the thermocouples to warm on the skin for up to 30 seconds before beginning the scan. Unfortunately, this does not change the immutable laws of thermodynamics (Zeroth). For example, let us say that the "acclimated" probes have now reached 88 degrees F and the scan is begun. As the 88 degree F probes encounter a hotter or colder area of the spine the contact of the probes will change the actual temperature of the skin, warming the cold area and cooling the hotter area, thus producing a false reading.

     Another complication associated with these instruments is that they have the propensity to produce hyperemia. The design of thermocouples necessitate that they be firmly cupped to the skin while the doctor glides the probes along its surface. This produces both friction and discomfort which causes the nervous system to respond reflexively with the production of hyperemia. Any discomfort will also cause the paraspinal musculature to contract or "tense up" in response. The combination of both of these responses can drastically alter the vascularity of the dermis, thus changing the true temperature of the skin and resulting in altered readings. The single problem inherent in the use of thermocouple instruments can be summed up in one word, contact. If contact with the skin could be avoided, none of the problems discussed above would occur.

     The use of non-contact paraspinal thermography was ushered in with the event of infrared (IR) sensor technology. Of historical note, IR technology was not available to our profession until the mid 1950's as it was classified by the military up to this time. The first use of infrared instrumentation in the chiropractic profession was introduced by Drs. Vernon Pierce and Glen Stillwagon in 1963 with the invention of the Dermathermograph (DTG). Since the DTG is only a single probed direct temperature scanner, and does not measure paraspinal differentials, it does not gather enough thermal data to make a proper paraspinal diagnostic interpretation.

     The initial IR units were crude at best. The sensitivity of the sensors was low and their use in the hairline was prohibited. Today, the newest digital infrared imaging scanners have taken paraspinal thermography to its highest level, while addressing all of the limitations associated with the thermocouple and early infrared scanners. These state-of-the-art units incorporate extremely sensitive (up to 1/100th of a degree F) and stable IR sensors, fiber optics, travel distance encoders, and computer thermal data processing. These new units house their sensors in a solid block of aluminum, which allows them to maintain their peak efficiency throughout each scan. Since the instrument is also non-invasive (non-contact), it produces no hyperemia thus making intra- and inter-examiner reliability studies a reality. Additionally, these scanners have the unique ability not only to record thermal differentials (right to left paraspinal thermal asymmetries) on the horizontal scale, but to also record direct temperatures on the vertical scale (absolute paraspinal temperatures of the right and left independently), a critical feature for proper "pattern" analysis. Computer thermal processing also allows the doctor to quantify the exact temperatures of all the "breaks", or thermal shifts, within the pattern. These new scanners are also designed to read accurately into the hairline and to the occiput without distortion. Another plus is that these units are extremely easy to use and can be mastered in a clinical setting in about a week. The incorporation of all of the above cutting-edge technology insures that the practicing field doctor can produce accurate, repeatable, and valid paraspinal thermographic scans.

     As mentioned before, the health care field is recognizing the need to monitor the nervous system’s function due to its unique role in the maintenance of global bodily function. Long term research by the scientific community has determined that the nervous system is a major, if not the major, contributing factor in the maintenance of health. Over 30 years of research and nearly 9,000 peer reviewed and indexed journal papers have confirmed thermography as a valid diagnostic test of real-time neurophysiology. Within the chiropractic and medical professions, such groups as the AMA Council on Scientific Affairs, ACA Council on Diagnostic Imaging, ICA Council on Diagnostic Imaging, American Academy of Pain Management, American Academy of Physical Medicine and Rehabilitation, Congress of Neurological Surgeons, and the American Academy of Head, Neck, Facial Pain, and TMJ Orthopedics have all issued policy statements confirming thermography's validity as a diagnostic imaging tool. The medico-legal system allows thermography to be introduced as court evidence. Thermography is accepted by federal agencies and departments as being valid and useful. Thermography is used across the United States in such prestigious centers as John Hopkins University School of Medicine, Georgetown University School of Medicine, Cedars-Sinai Medical Center, and Tulane University, to name a few. Overseas, thermography is used at the Louis Pasteur Institute in Paris, University of Copenhagen, Verona Italy University Hospital, and Yeshiva University Medical School in Tel Aviv. The weight of the evidence indicates that thermography is a valid scientific procedure.

     With the increasing costs of running a practice concerning many clinicians today, incorporating thermography into patient care becomes a viable issue. The cost effectiveness of paraspinal infrared thermography is quite evident when compared to camera systems. If the clinician is primarily concerned with investigating the spine (CNS and/or immediate PNS) as the cause, then paraspinal infrared thermography is all thats needed. Even if a radicular problem presents itself, the extremity dermatome/thermatome will not be thermally positive without the concomitant paraspinal area being positive also. This becomes significant when the costs of paraspinal infrared themography and camera systems are weighed. With more and more doctors turning to objective diagnostics and results oriented (outcome based) care, the need for paraspinal thermography is quickly outweighing cost concerns.

     Today, the digital infrared imaging scanner of the 1990's represents the epitome of research and technology in paraspinal thermography. Nearly 9,000 peer-reviewed papers in the past 30 years have established digital infrared imaging as the new standard in sub-threshold neurodiagnosis, thus rendering the thermocouple technology of the past obsolete. If the chiropractic profession is going to continue to stand on its core principle that the subluxation, and it's adjustment, does affect the neurophysiology of the body, it becomes absolutely necessary as responsible clinicians to monitor its function using the best technology the world has to offer. Through the use of paraspinal thermography we as a profession have the unique opportunity to establish neurophysiological responses as the major factor within the subluxation complex, thus expanding the boundaries of the chiropractic practice beyond aberrant spinal biomechanics to the boundless limits of the nervous system itself.