- Thermography in Fibromyalgia
- Usefulness of Thermography in Diagnosis of Complex Regional Pain Syndrome Type I After Transradial Coronary Intervention
- The role of infrared thermal imaging (ITI) in management of neuropathic pain
- Infrared Thermographic Vasomotor Mapping and Differential Diagnosis
- Infrared Thermography in Pain Medicine
- Parameters of thick and thin nerve-fiber functions as predictors of pain in carpal
- A Review on Inflammatory Pain Detection in Human Body through Infrared Image Analysis
K.Ammer, T.Schartelmüller, P.Melnizky
Ludwig Boltzmann Forschungsstelle für Physikalische Diagnostik im Hanuschkrankenhaus, Heinrich Collinstr. 30, A-1140 Wien, Austria
A high number of tender points, which may correlate well with hot spots in thermograms, is an essential criterium for the diagnosis of fibromyalgia.
A study in 18 patients diagnosed as fibromyalgia by the criteria of the American College of Rheumatology was made to determine the number of hot spots in these patients. The patient findings were compared with those of a group of healthy subjects and also a group of pain patients which did not meet the diagnostic features for fibromyalgia.
Thermograms of the regions typical for the location of tender points were recorded after acclimatization for 15 minutes to a room temperature of 24°C. Hot spots were defined as any small area being at least 0.5 degrees warmer than the surroundings. After thermography the typical sites for tenderness were tested.
As expected, the number of tender points differed significantly between fibromyalgic patients and both control groups. Furthermore the number of hot spots was higher in patients with fibromyalgia than in healthy controls. However, there were less hot spots than tender points, and a general coincidence of hot spots with tender points was seldom found. Although the number of hot spots is increased in patients suffering from fibromyalgia, the number of tender points on the patient can not be replaced by recording hot spots in thermograms.
There is growing interest in diagnostic criteria for diagnosing fibromyalgia, formerly called fibrositis. In 1990 the American College of Rheumatology (ACR) published a revision of diagnostic criteria, which are mainly based on a high number of tender points tested over 18 defined sites 1). In the late seventies Smythe had already proposed 14 specific areas to prove tenderness in fibromyalgic patients 2). There is some evidence in the literature, that tender points correlate well with hot spots in infrared thermograms. This was shown for patients with epicondylitis 3). A. Fischer was able to prove that hot spots are characterized by a significant lower threshold for pressure pain than the contralateral side of the body without a hot spot 4). This phenomenon was also found in epicondylitis 5) and myofascial pain syndromes 6), but was not seen by Swerdlow and Dieter checking hot spots in other parts of the body7).
We therefore investigated the thermograms of patients with clinically proven fibromyalgia to see if they also show a high frequency of hot spots compared to healthy subjects or pain patients, which did not fulfill the criteria for fibromyalgia.
Out-door patients were included in the study. After recording the history, the tenderness of typical sites, as defined by Smythe, were checked.
The diagnosis of fibromyalgia was made in cases of widespread pain for at least 3 months, sleep disturbances and either slight depressive mood or decreased work ability and a minimum of 8 tender points. Patients, who did not meet these criteria, were diagnosed as localized myofascial pain syndrome. In addition, in 7 healthy female subjects the tenderness of typical sites for fibromyalgia was checked. The investigated sample fell into 3 groups: 1 group suffering from fibromyalgia, 1 group with localized myofascial pain syndrome and one of healthy controls.
1 to 3 days after the first clinical investigation, a series of thermograms was performed on all participants of the study, at a room temperature of 24 degrees and acclimatization for 15 minutes without clothes.
Images were taken from the neck (both lateral views), from the chest (front view), from the shoul-der-girdle (back view) , both elbows and forearms (lateral view) , from the lumbar spine and the buttocks (back view), thighs and knees with one foot in front of the other (lateral view).
Either an Agema 870 or an NEC San-ei Thermo tracer, both electronically cooled Infrared-Scanners, were used for imaging.
After thermography, the tenderness of typical sites was checked and recorded again by either a physiotherapist or a research nurse.
Thermal images were modified by a low pass filter and then checked for hot spots. A hot spot was defined as a small region at least 0,5 degrees warmer than the surroundings. Only hot spots located nearby the sites checked for tenderness were accepted. Hot spots originating from varicose veins were not included in the findings.
The number and location of tender points and hot spots were compared statistically within and between all groups of investigated subjects.
The fibromyalgic patients were significantly older (Kruskal-Wallis 1 way Anova: p=0,0002), showed a higher number of tender points (Kruskal-Wallis 1 way Anova: p<O,0001) and more hot spots (Kruskal-Wallis 1 way Anova: p<0,0001) than the other both groups.
A significant higher number of tender points was detected in patients with localized pain syndrome than in healthy controls (Mann-Whitney-U-Test, 2-tailed p=O,007). However, both groups were neither significantly different in the number of hot spots (Mann-Whitney-U-Test, 2-tailed p=0,50) nor age (Mann-Whitney-U-Test, 2-tailed p=0,15). Coincidence of tender points and hot spots
After computing positive hot and tender points together into one data file of all investigated sites, the number of tender points and hot spots differed significantly (McNemar Test p= 0.037). This was caused by the fact that over 74 points, a hot spot was seen over a non tender site, and at 98 sites a hot spot was missed over tenderness. On the remaining 308 sites, 132 hot spots were localized over tenderness and on 176 sites neither pain on pressure nor hot spots were detected.
Diagnostic accuracy (defined by the percentage of true positive and true negative cases) ranged between 83,8 ‘% (Left trapezius) and 54,8 % (low cervical sites, left knee) for the total sample.
The findings of the study showed clearly, that fibromyalgic patients present a significantly higher number of hot spots over specific sites than either patients with localized pain syndromes or healthy controls. Although both control groups differed in the number of tender points, these sub-samples could not be distinguished by the number of hot spots.
Two established sites for checking muscle tenderness, are extremely difficult 10 assess by thermography. Because varicose veins can very often be found on the medial knee site, i1 is almost impossible, in this region, to correlate muscle tenderness with hot spots. On the lateral view of the low cervical spine, the heat from the upper thoracic wall causes similar difficulties for interpretation.
As far as one can conclude from the small number of cases in this study, there might be an overlap in number of hot spots between fibromyalgic patients and even healthy controls. For example, one young women without any tender points presented as many as 7 hot spots over specific sites. Taking in account the clinical experience that fibromyalgia appears together with specific personal traits, one is tempted to speculate, whether hot spots might precede the disease before it is fully developed.
Following this idea, the high number of hot spots in some subjects of the control groups, was not unexpected.
Nevertheless, patients with whole body “speckled” thermograms, meaning a high number of hot spots, should be suspected of suffering from fibromyalgia. In those patients, a typical history and the count of tender points will finally confirm this diagnosis in most cases.
1 ) Wolfe F et al: The American College of Rheumatology 1990 Criteria for the classification of fibromyalgia. Arthritis Rheum 33: 160-171, 1990
2 ) Smythe HA: ‘Fibrositis’ as a Disorder of Pain Modulation. Clin Rheum Dis 5: 823-832, 1979
3 ) Binder AI et al: Thermography of Tennis Elbow.ln:Ring EFJ, Phillips B (eds): Recent Advances in Medical Thermology, pp, Plenum Press, New York, Londson, 1994
4 ) Fischer AA, Chang CH: Temperature and Pressure Threshold Measurements in Trigger Points. 1: 212-215
5 ) Ammer K: Thermal Evaluation of Tennis Elbow. In. Ammer K, Ring EFJ (eds): The Thermal Image in Medicine and Biology, Uhlen Verlag, Wien (in press)
6.) Kruse RA jr, Christansen JA: Thermographic imaging of myofascial trigger points. A Follow-up study. 73:819-823, 1992
7 ) Swerdlow B, Dieter JNI: An evaluation of the sensitivity and specificity of medical thermography for the documentation of myofascial trigger points. PAIN 48, 205-213,1992
USEFULNESS OF THERMOGRAPHY IN DIAGNOSIS OF COMPLEX REGIONAL PAIN SYNDROME TYPE I AFTER TRANSRADIAL CORONARY INTERVENTION
Min-Young Jeong, MD, Jin-Sok Yu, MD, Woo-Baek Chung, MD
Volume 25 – Issue 9 – September, 2013
Complex regional pain syndrome (CRPS) is a very rare complication of transradial coronary intervention (TRI). We present the case of a 51-year-old man who suffered severe pain of the right forearm after TRI and progressed to type I CRPS. The patient had effort angina and underwent successful coronary artery stent deployment on the right coronary artery. After removing the hemostatic device, the patient had swelling and severe pain that was not relieved by analgesics. Continued pain progressed to allodynia, hyperalgesia, and hyperesthesia, which met the diagnostic criteria for CRPS. Electromyography showed no abnormalities in nerve conduction and thermography of the forearm showed temperature discrepancy between both forearms, which confirmed the diagnosis of CRPS. We treated the patient with sympathetic nerve block, but he still suffers from minor pain in the right forearm. This case demonstrates that unalleviated pain after TRI can progress to CRPS, and that thermography is a useful method to diagnose CRPS.
J INVASIVE CARDIOL 2013;25(9):E183-E185
Transradial coronary intervention (TRI) is now a widely utilized technique and is considered a relatively safe procedure compared to the transfemoral approach. Distinguishing anatomical features of the radial artery puncture site, namely, its placement over the radius bone and the absence of any major veins or nerves located near the artery, provide advantages to hemostasis after the procedure. Nonetheless, radial artery occlusion does occur, with a reported incidence of 4.4% at an early stage and 3.2% after 1 month. The incidence of radial artery hematoma has also been reported, with an incidence of approximately 5%.3 The dual vascular supply of the palmar region prevents vascular complications from resulting in pain or ischemic changes. The incidence of complex regional pain syndrome (CRPS) from vascular interventions is extremely rare; only 3 cases of CRPS after TRI have been reported in the literature. The case presented here, which demonstrated the typical thermographic findings of CRPS, is the first report of CRPS after TRI diagnosed by thermography.
A 51-year-old man with chronic stable angina was referred to our hospital for management of 70% tubular stenosis at the mid-portion of the right coronary artery (RCA) revealed by computerized tomographic coronary angiography at another hospital. He had a smoking history of 35 pack years and was diagnosed with diabetes and hypertension 10 years ago, which had been treated with antiglycemic (metformin 1000 mg) and anti-hypertensive (amlodipine 5 mg) agents. The patient’s initial electrocardiography, chest x-ray, and routine laboratory studies were all within normal limits. A TRI was scheduled for confirmative diagnosis and treatment. Allen’s test of the right hand, performed before the procedure, was normal. The right radial artery was punctured and a 6 Fr radial sheath was accessed. An everolimus-eluting stent was successfully deployed at the RCA lesion without event (Figure 1). A hemostatic device (TR band; Terumo Corporation) was applied. Fifteen mL of air were inflated after removing the radial sheath and 3 mL of air were deflated every 2 hours thereafter. The TR band was removed 6 hours later without any complications. However, 4 hours after TR band removal, the patient complained of mild, dull pain and swelling at the puncture site; tramadol (150 mg) was prescribed. Three days after TRI, the patient was discharged from the hospital. One week after discharge, the patient visited an outpatient clinic with complaint of severe continuous stabbing pain at the puncture site that radiated to the right upper arm and shoulder. Swelling of the puncture site extended to the upper arm, though the right radial pulse was intact. We treated the pain with acetaminophen (975 mg) and gabapentin (1500 mg). Swelling of the arm spontaneously resolved after 1 week, but medication did not alleviate the pain. One month later, the patient complained of continuous pain in the right hand, arm, and shoulder, hyperesthesia in the right fingers, and difficulties in performing normal daily activities, such as driving and using chopsticks. An electromyography was performed to determine nerve damage, and showed no abnormalities on either motor or sensory nerve conduction studies. An F-response was performed and showed normal latency range in all tested nerves, while a needle electromyography did not reveal evidence of abnormal resting denervation potentials for any of the tested muscles. Right brachial arteriography was performed to evaluate vascular complications and radial arterial occlusion was noted. Thermography was then performed to evaluate the chronic pain, which demonstrated that the temperature at the pain site was 2 °C higher than the unaffected left arm. Findings from thermography suggested that the chronic pain was due to reflex sympathetic tone abnormality because ischemia may lower the temperature at the pain site. Based on the diagnostic criteria established by the International Association of the Study of Pain, type I CRPS was a possible diagnosis, and thermographic findings were confirmative. The patient was treated with cervical epidural block and repeated right stellate ganglion blocks, and prescribed 1800 mg of gabapentin, 10 mg of nortriptyline, 200 mg of revaprazan, and 10 mg of hydromorphone. Twelve months after treatment, the patient was still suffering from mild pain, but improvement was noted in the patient’s ability to perform daily activities.
By definition, CRPS results from neuropathic pain derived from abnormalities of the sympathetic nervous system. CRPS is diagnosed by a constellation of subjective symptoms, including immobilization, continuous pain, allodynia, hyperalgesia, hyperesthesia, and vasomotor symptoms. All other conditions that would otherwise explain the degree of pain and/or dysfunction must be excluded. There are two sub-types of CRPS: type I is with no identifiable nerve injury and type II is with a history of an identifiable nerve injury. A diagnosis of CRPS is further supported by the relatively higher temperature of the pain-affected area; increased sympathetic activity is the reason for the higher temperature. If the forearm pain was the result of limb ischemia, thermography of the forearm should demonstrate a lower temperature. The thermographic findings of this case suggested that right radial artery occlusion did not affect the development of the intractable pain. Thermography is an effective modality for assessing increases in reflex sympathetic tone and was recently proven to have a high sensitivity and specificity in diagnosing CRPS. Two degrees Celsius higher temperature in the pain-affected area demonstrated a diagnostic sensitivity of 73% and specificity of 94%.
Papadimos et al reported a case of type I CRPS secondary to radial artery occlusion, after 20 hours of compression by hemostatic device (Hemaband; TZ Medical). Sasano et al also reported a case of type II CRPS that was associated with a post-TRI median nerve injury resulting from excessive compression. Lai et al reported a case of type II CRPS due to a median nerve injury after TRI, diagnosed by plethysmography, electromyography, and nerve conduction studies. There was only 1 previously reported case of type I CRPS; in that case, pain developed from prolonged and excessive compression of the puncture site and was diagnosed by the pain criteria of the International Association for the Study of Pain. None of the previous cases described remarkable arm swelling, which was a suggestive finding of hematoma. However, in this case, radial artery hematoma was the main cause of pain. Puncture site swelling after removal of the hemostatic device and extension to the upper arm suggests there was hematoma. This may result in prolonged compression of the radial artery and increased pressure in the carpal tunnel. Acute pain developed from ischemia secondary to radial artery occlusion and compression of nerves, lasted more than a week and progressed to chronic pain, which eventually aggravated to CRPS. Acute severe pain and arm swelling after TRI should be considered for compartment syndrome, but in this case, arm swelling was not so severe and resolved spontaneously. Thermography demonstrated meaningful information for confirmative diagnosis of type I CRPS in this case.
We presented the first thermographically diagnosed case of post-TRI type I CRPS. The patient suffered intractable pain and arm swelling immediately after TRI, and was treated with analgesics. Arm swelling resolved spontaneously, but unalleviated pain lasted for a considerable time period. Allodynia, immobilization, and hyperesthesia developed in the right arm, and type I CRPS was confirmed by normal electromyography findings and abnormal thermography findings. The clinical course of the patient suggests that pain after TRI should be treated thoroughly and swelling of the puncture site should not be neglected, because it can progress to serious complications such as CRPS. Moreover, this case demonstrates that reflex sympathetic tone dysfunction can be effectively examined by thermography, a modality also helpful in diagnosing CRPS.
1. Kiemeneij F, Laarman GJ, de Melker E. Transradial artery coronary angioplasty. Am Heart J. 1995;129(1):1-7.
2. Kiemeneij JF, Laarman GJ. Percutaneous transradial artery approach for coronary Palmaz-Schatz stent implantation. Am Heart J. 1994;129:167-174.
3. Rathore S, Morris JL. The radial approach: is this the route to take? J Interv Cardiol. 2008;21(5):375-379.
4. Papadimos TJ, Hofmann JP. Radial artery thrombosis, palmar arch systolic blood velocities, and chronic regional pain syndrome 1 following transradial cardiac catheterization. Catheter Cardiovasc Interv. 2002;57(4):537-540.
5. Sasano N, Tsuda T, Sasano H, Ito S, Sobue K, Katsuya H. A case of complex regional pain syndrome type II after transradial coronary intervention. J Anesth. 2004;18(4):310-331.
6. Lai CJ, Chou CL, Liu TJ, Chan RC. Complex regional pain syndrome after transradial cardiac catheterization. J Chin Med Assoc. 2006;69(4):179-183.
7. Krumova EK, Frettlöh J, Klauenberg S, Richter H, Wasner G, Maier C. Long-term skin temperature measurements — a practical diagnostic tool in complex regional pain syndrome. Pain. 2008;140(1):8-22.
8. Novljan G, Rus RR, Koren-Jeverica A, Avčin T, Ponikvar R, Buturović-Ponikvar J. Detection of dialysis access induced limb ischemia by infrared thermography in children. Ther Apher Dial. 2011;15(3):298-305.
9. Harden RN, Bruehl S, Galer BS, et al. Complex regional pain syndrome: are the IASP diagnostic criteria valid and sufficiently comprehensive? Pain. 1999;83(2):211-219.
10. Bruehl S, Harden RN, Galer BS, et al. External validation of IASP diagnostic criteria for complex regional pain syndrome and proposed research diagnostic criteria. Pain. 1999;81(1-2):147-154.
11. Bruehl S. An update on the pathophysiology of complex regional pain syndrome. Anesthesiology. 2010;113(3):713-725.
Hooshang Hooshmand, M.D. , Masood Hashmi, M.D. , and Eric M. Phillips
Neurological Associates Pain Management Center
1255 37th Street, Suite B
Vero Beach, Florida, USA.
The value of Infrared thermal imaging (ITI) is limited to evaluation of neurovascular dysfunction. It provides useful diagnostic and therapeutic information in the management of neuropathic pain. Key Words: Infrared thermal imaging, neuropathic pain, ITI in pain management.
The nociceptive chronic pain is usually due to involvement of large somesthetic (somatic) nerve fibres. Electromyography (EMG) and nerve conduction velocity (NCV) tests are usually the diagnostic tools for the study of somesthetic pain. In contrast, these tests are normal in neuropathic pain because they can not detect changes in the microscopic thermosensory neurovasculature. The diagnosis and management of neuropathic pain requires neurovascular autonomic tests such as infrared thermal imaging.
The role of ITI in pain management was studied in 762 successive complex pain patients evaluated with ITI. The results were compared with a meta analysis of medical literature. A Bales Scientific Infrared Thermal Processor and an Agema (Flir) Infrared Thermal Processor were utilized in this study. The patients were cooled down in a 20-21ºC steady state room for 30 minutes of equilibration without clothing. No prior smoking for 90 minutes. A standard sensitivity of 24-34ºC was done. If the areas were not properly visualized the physician would adjust the sensitivity accordingly. Two identically reproducible images recorded on laser disc were required.
The study revealed the importance of proper technique and proper clinical correlation. ITI is useful in the study of complex neuropathic pain. It provides indispensable diagnostic and therapeutic information. Both superficial and deep temperature changes influence the ITI test. The skin is an almost perfect radiator of both deep and surface heat. This radiator, has 98% emissive efficiency. The ITI records pathological temperatures at least as deep as 27 mm in the extremities, and even deeper in the breast.
ITI exclusively provides diagnostic information in neuropathic pain. Such information cannot be achieved by EMG or NCV. ITI is useless in diagnosis and management of cervical and lumbar sprain. It can spare patients from unnecessary amputation, carpal tunnel, temporomandibular joint, spinal disc surgeries and migraine. It is helpful in differentiating cervicogenic headache from migraine-each requiring opposite forms of treatment. In electrical injury ITI identifies points of entrance and exit of electricity. This picture is pathognomonic and is exclusively seen in electrical injury. ITI identifies hyperthermic foci of permanent sympathetic system damage sparing the patient from further damage by trauma of sympathetic nerve blocks.
1. Hooshmand H: Is thermal imaging of any use in pain management? Pain Digest. 1998; 8:166-170.
2.Elam R, Goodwin DN, Lloyd-Williams K: Optical properties of human epidermis. Nature [Lond]. 1963; 198:1001.
3. Lawson RN: Thermography- a new tool for the investigation of breast lesions. Can Med Assoc J. 1957; 13:517- 524.
4.Thermography and its clinical applications. Annals of the New York Academy of Science. 1964; 121: 304.
5. Ring EFJ: Progress in the measurement of human body temperature. IEEE Engineering in Medicine and Biology . July/August 1998; pp19-24.
Robert G. Schwartz, MD
When performed with proper technique and under controlled conditions, thermography (Computerized Infrared Imaging or CII) is the test of choice for mapping of vasomotor instability and asymmetry. The findings provide important clinical insights into those structures that generate aberrant sympathetic responses for pain syndromes such as Reflex Sympathetic Dystrophy (RSD), Complex Regional Pain Syndrome types I and II (CRPS), Thoracic Outlet Syndrome (TOS), Cervical Brachial Syndrome, Fibromyalgia, and Barre-Lieou. In addition, the presence of abnormalities and the distribution of findings can be invaluable in differential diagnosis of these conditions.
The medical community has demonstrated increased awareness of sympathetic pain syndromes over the last decade. New interventions and approaches toward alleviating symptoms in those afflicted have been tried, some with success. Even better results can be achieved through a greater understanding of which structure is initially responsible for generating the condition.
The sympathetic system, which is largely responsible for the control of surface skin temperature, innervates all tissue of mesodermal and ectodermal origin. For non-visceral soft tissues, this includes muscle, ligament, synovium, tendon, fascia, dura, disc, and peripheral nerve fibers. Other less obvious but equally important structures, such as interosseous membrane and neuro-lymphatic sphincters, can be richly innervated by the sympathetic system as well. Essentially, the innervation of the sympathetic system is ubiquitous.
Since one of the primary functions of the sympathetic system is to monitor those tissues that it innervates, it is not surprising that when an injury occurs to one of those structures, the system may occasionally function improperly. Why this occurs remains speculative, but the net result is an alteration in trans-membrane electric potential of the affected sympathetic nerve fibers. Direct structural injury, vascular ischemia, infection, and coagulopathy are just a few of the mechanisms that might lead to such an alteration.
From a thermographic perspective, what is important is whether the resultant vasomotor response is great enough to create a change in skin temperature of greater then 1º C compared to the contralateral side or with respect to the surrounding dermatome, sclerotome, or vasotome. While dermatomes represent the distribution of sensory nerve fibers upon skin, a sclerotome reflects the distribution of skin galvanic impedance influenced by a visceral or non-visceral soft tissue structure. Numerous sclerotomal patterns exist. Examples of clinical conditions with identified sclerotomal patterns (often described as referred pain) include facet syndromes, myofascial, ligament, and dural pain syndromes.
It is important to recognize that while sclerotomal patterns frequently mimic pain patterns such as herniated disc, they are not at all pathognomonic for the same. For example, a fibulocalcaneal ligament strain may very well have thermographic change that tracks in an L5 distribution, but that does not mean that the L5 nerve root or disc is the source of those findings. While the nerve root or disc may be the source, all structures that refer within that sclerotome must be considered when deciding which structure is responsible for the abnormality.
Likewise, it is important to understand that treating any structure within the sclerotome may actually correct the abnormality. Sometimes all that is required to restore skin galvanic impedance to normal, and its associated vasomotor instability or asymmetry, is to remove the stimulus that initially generated the sympathetic response. This may mean an injection of a medicine into a torn ligament that stops inflammation or repairs the tear, or of a neurolytic agent that alleviates a persistent non-physiologic contraction of muscle. Naturally, other examples exist, such as hyaluronidase injection into a knee, and oral or topical medications that restore blood flow and modulate sympathetic tone.
Not withstanding the above, there is also every reason to believe that treating cephalad to the most proximal portion involved will be more effective then treating caudal to it. The medical literature is replete with references demonstrating the benefit of spinal blocks for sympathetic pain syndromes. It is not, however, as clear why some blocks are more successful then others.
If a lumbar thermographic study demonstrates vasomotor asymmetry that tracks in an L34 dermatome or sclerotome, it would be reasonable to speculate that a sympathetic block at L3 would be more effective then an epidural block at L5. In addition, if the original injury was in the ankle at the medial collateral ligament of the knee, then a concurrent injection with intensive physical therapy at that locale may prove to be even more rewarding than either intervention alone. By obtaining thermographic imaging, powerful answers as to the extent and distribution of involvement can be obtained.
The thermographically generated vasomotor map also provides invaluable information for therapeutic decision-making when treatment previously based upon it fails. For example, if a lumbar block does not produce pain relief in an L5 vasomotor-mapped patient, the patient may still show dramatic response to a peroneal nerve block (another L5 innervated structure). A combination of expertise in the basic anatomy of those structures that can exert influence in the distribution of the vasomotor abnormality found, and the ability to objectify where the vasomotor asymmetry actually occurs, allows for a more rational approach to intervention that is otherwise not available.
Vasotomes represent another pattern of abnormality that the examiner must understand. They should not be confused with vasomotor instability of sympathetic origin. Vasotomes are not dependent upon sympathetic control of skin galvanic impedance, cutaneous vasculature or sweat glands, but rather represent peripheral vascular supply zones.
Likewise, local inflammatory conditions, such as a hot joint in rheumatoid arthritis or erythema associated with a rash should not be confused with local vasomotor dysfunction under sympathetic influence. By completing a full thermographic study (bilateral extremities from multiple views and corresponding spinal segments), it is not at all difficult to differentiate local inflammatory, venous, or peripheral artery abnormalities from sclerotomal or dermatomal patterns.
A normal study is also clinically helpful. It is not uncommon for a patient to be given a diagnosis of CRPS/RSD and yet be non-responsive to sympathetic block. Prolonged, hopeless medical management or invasive procedures such as spinal cord stimulators can result. A normal study helps rule out the original diagnosis, or at least suggests that a sympathetically independent pain syndrome may exist.
A localized thermographic pattern inconsistent with other recognized patterns can provide useful information as well. For example, when warming is present in the dorsolateral aspect of the foot alone, the examiner should look for a missed fibulotalo ligament strain that, when treated, may be miraculously responsive. Since sympathetic variants such as the Angry Backfiring C syndrome (where a backfiring of the C fiber results in excess Substance P accumulation) may also create a similar picture, differential diagnostic skills must still be employed.
“While dermatomes represent the distribution of sensory nerve fibers upon skin, a sclerotome reflects the distribution of skin galvanic impedance influenced by a visceral or non-visceral soft tissue structure.”
In the case of ABC syndrome, sympathetic block may not only fail, but can create a paradoxical worsening of symptoms, as the painful part is already vasodilated. In this instance a pharmacologic approach that is intended to deplete Substance P or target receptors responsible for vasoconstriction, or employment of electric sympathetic block (where different aspects of the voltage gate can be targeted) may prove more effective then a chemical sympathetic block. Whenever a paradoxical response to sympathetic block occurs, this should be kept in mind.
In addition to objectifying the presence of a paradoxical effect, Infrared Thermographic monitoring during blockade can be quite helpful in assessing if intended ipsilateral vasodilatation was accomplished. Even when a Horner’s is observed with a stellate block, as many as 40% of patients do not get limb vasodilatation. Their lack of clinical responsiveness to the block may lead to a false impression that CRPS/RSD does not exist.
The Triple C syndrome, consisting of cold hypesthesia, cold allodynia and cold skin, is another localized sympathetic variant. As expected, with this syndrome Infrared Thermographic imaging reveals a localized cold asymmetry pattern. The more distal the occurrence of this syndrome, the less responsive the patient is to a spinal block. With Triple C syndrome, combination interventions, including localized therapy and pharmacologic agents, should be more aggressively used.
Diffuse vasomotor instability involving an entire limb or limb segment, and not confined to a particular dermatome or sclerotome, is a hallmark finding of a true RSD syndrome. Dural, neuro-immuno-infectious interactions and multiple generators should be aggressively investigated. While any case of sympathetic pain with vasomotor instability can spread, when diffuse vasomotor asymmetry exists, symptomatic intervention with an eye towards prevention of spread, limb trophic changes, edema, contracture or Sudeks atrophy should be emphatically employed.
Stopping progression is one of the most effective treatments a physician has to offer in the treatment of CRPS/RSD. Early diagnosis, due to high sensitivity, is one of the great advantages that thermography offers over triple phase bone scan or diagnostic block in the management of sympathetic pain syndromes. Findings of diffuse vasomotor asymmetry should alert the physician to intercede promptly to interrupt the progression of CRPS/RSD toward stages two and three.
The physician must keep in mind that thermography is no different than any other objective study. Ultimately, it is always best to treat patients based upon both clinical and diagnostic impressions, not test results alone. This approach will help avoid the potential pitfall case wherein a localized, or clearly defined, asymmetry pattern unexpectedly shows rapid progression to escalating stages.
The International Association for the Study of Pain (IASP) has published diagnostic criteria for the diagnosis of CRPS types one and two and revisions have already been suggested. Whether the revised clinical and research criteria, or the original criteria are used, objective signs of vasomotor instability (changes in skin blood flow or evidence of temperature asymmetry) remain a diagnostic criterion. This is important as it is well established that palpation alone is a poor way to assess for skin temperature change.
In addition to being insensitive, palpation provides no ability to map the distribution of those changes. In cases where allodynia, hyperalgesia or barometric weather sensitivity exist, only thermography offers the ability to objectify if the vasomotor instability criterion is satisfied. In addition, the American Medical Association’s “Guides to the Evaluation of Permanent Impairment” recognizes that “…regional sympathetic blockade has no role in the diagnosis of CRPS.” Instead, it cites objective criteria inclusive of vasomotor change.
Perplexed by the CRPS/RSD patient, “The Guides” suggest rating impairment based on alteration in activities of daily living, loss in motion of each joint involved, sensory and motor deficits for the nerve involved or sensory deficits, loss of power, and pain for the body part involved. While this approach attempts to sidestep the problem of objectifying which body part is involved, it is still left to the physician to address the issue.
In this light, the body part involved becomes not only a clinical issue, but also a medical-legal one. Just as a post-stroke, shoulder-hand syndrome patient may present with a swollen hand and be unable to communicate that there is proximal pain, a patient with a crush injury to the hand cannot be expected to articulate that he has vasomotor instability as far proximal as the shoulder or that the perception of compensatory proximal pain is actually sympathetic involvement of the entire limb.
Only after vasomotor mapping has been completed can the distribution of asymmetry be fully determined and the question of which body part is involved be properly addressed. There are many other difficult situations in which thermography is extremely useful in objectifying the extent or presence of involvement. These include thoracic outlet syndrome, cervical-brachial syndrome, vasomotor headache, atypical facial pain, the posterior cervical sympathetic syndrome of Barre-Leiou, and failed back syndrome.
While a sympathetic component should be considered in each of the aforementioned conditions, TOS deserves special attention. Patients who suffer from this malady often undergo extensive workups only to find the results to be negative. X-ray examination for a cervical rib is only found in a minority of cases and, when present, an even smaller number of cases show positive arteriograms.
Although other conditions that may be confused with TOS, such as radiculopathy or ulnar neuropathy, may be exposed, electrodiagnostic studies are usually not diagnostic for TOS. The vast majority of TOS cases are not due to overt vascular or lower trunk neurologic pathology, but rather secondary to numerous musculoskeletal conditions such as scalene anticus spasm, scapulothoracic dysfunction with resultant tension or mechanical torque across the thoracic outlet, and cervical-thoracic interspinous ligament strain with reflex myotomal spasms or myosfasical pain.
“Thermography is no different than any other objective study. Ultimately, it is always best to treat patients based upon both clinical and diagnostic impressions, not test results alone.”
Irrespective of which of these somatic issues is the source, patients complain of cold, burning, numb sensations, typically radiating from the neck or shoulder down the medial aspect of the arm and into the fourth and fifth fingers. In some cases, vasomotor instability is visible to the naked eye with obvious skin color changes. These patients frequently respond to a stellate or cervical plexus block.
Thermography is the obvious test of choice to objectify the presence or absence of a vasomotor instability consistent with TOS. Many surgeons have an aversion toward operating upon the TOS patient. In the absence of an absolute surgical indication for TOS, such as an obvious cervical rib that creates clear-cut stenosis on arteriography, thermography is the most cost-effective and diagnostic approach.
A positive study clearly demonstrates a heat emission asymmetry pattern across the medial aspect of the arm and forearm. Radiation to the medial aspect of the fourth and fifth fingers may be present as well. If a study is positive, and the clinician feels the need, then an apical chest X-ray to assess for cervical rib or arteriography can always be obtained later on.
Thermography is ideally suited for diagnosing Barre-Lieou, another common condition. There is no other diagnostic study that can objectify the presence of associated vasomotor instability. In Barre-Lieou, the posterior cervical sympathetic chain generates aberrant impulses that can result in facial heat emission asymmetry patterns.
There are several possibilities as to why the syndrome occurs, including a direct traction injury on the chain as in a whiplash-type injury, ischemia, or hidden infection. In any event, the result is recalcitrant head and neck pain — with or without scapulo-thoracic pain — associated with blurred vision, tinnitus, vertigo, or nausea.
Barre-Lieou is frequently responsive to sympathetic block. Infrared thermographic imaging of the face, cervical spine, and extremities effectively demonstrates vasomotor asymmetry in these cases. Through its unique mapping ability, thermography can also provide the physician with insight into which somatic level is responsible for the abnormality.
While proving the presence of heat emission asymmetry has great clinical significance, the benefit of objectifying its absence should not be overlooked. When criteria for CRPS are satisfied, but there is no vasomotor abnormality as with RSD, sympathetic independent pain should be more seriously considered. In this instance, relief from sympathetic block is far less likely and alternate conditions or interventions should be considered.
Secretan’s Syndrome, which consists of post-traumatic peritendonous fibrosis, brawny edema, loss of finger extensor function, and trophic skin changes, is a relatively uncommon disorder that can mimic CRPS/RSD. This condition has no vasomotor or sudomotor component, so Infrared Thermographic imaging will be negative.
Glomus tumor of the hand, due to neuro-myoarterial tumor formation, is associated with excruciating distal finger pain, cold intolerance, and pain triggered by palpation. Abnormal blood flow in the distal phalanx does occur, but typical vasomotor asymmetry patterns do not.
If it were not for the unique qualities of medical thermography, the information obtained by it would not be otherwise available. Failure to consider the objective information made available by thermography limits clinical assessment and rational decision-making when developing a treatment approach for relevant conditions. Thermography is a unique imaging study that provides the physician with invaluable information in the diagnosis, treatment, and management of patients with suspected or bonafide sympathetic pain syndromes.
1. American Academy of Thermology, Practice Guidelines Committee. Guidelines for Neuromusculoskeletal Thermography, Wheeling, WV, 2006
2. American Medical Association. Guides to the Evaluation of Permanent Impairment, American Medical Association, Chicago, 2000.
3. Bersani F, Ed. Electricity and Magnetism in Biology and Medicine, Kluwer Academic/Plenum Publishers, New York, 1999.
4. Bonica JJ. The Management of Pain, Second Edition, Lea & Febiger, Philadelphia, 1990.
5. Borenstein DG, Wiesel SW, and Boden SD, Eds. Low Back and Neck Pain, Third Edition, W. B. Saunders, Phildelphia, 2004.
6. Cousins MJ, Bridenbaugh PO, Eds. Neural Blockade in Clinical Anesthesia and Management of Pain, Second Edition, Lippincott, Philadelphia, 1998.
7. Cyriax J. Textbook Of Orthopedic Medicine, Bailliere Tindall, Philadelphia, 1982.
8. Friedman MS. The Use of Thermography in Sympathetically Maintained Pain. Iowa Orth J, 1994;14:141-7.
9. Gayral L and Neuwirth E. Oto-Neuro-Opthalmologic Manifestations of Cervical Origin – Posterior Cervical Sympathetic Syndrome of Barre-Lieou. New York State Journal of Medicine, 1954;1920-6.
10. Gonzalez, E. The Nonsurgical Management of Acute Low Back Pain, Demos Vermande, New York, 1997.
11. Govindan S. Infrared Imaging of Extracranial Microcirculation: A Review. Thermology International, 2003;13:91-98. Rehabilitation Medicine and Thermography 45
12. Gray H. Gray’s Anatomy, S. Standring, Editor-in-Chief. Elsevier Churchill Livingstone, New York, 2004.
13. Gulevich SJ, Conwell TD, Lane J, et al. Stress Infrared Telethermography is useful in the diagnosis of complex regional pain syndrome, type 1 (formerly reflex sympathetic dystrophy). Clinical Journal of Pain, 1997;13:50-59.
14. Hooshmand H. Chronic Pain: Reflex Sympathetic Dystrophy Prevention and Management, CRC Press, Boca Raton, Florida, 1993.
15. Klippel JH and Dieppe PA, Eds. Practical Rheumatology. Mosby, Baltimore, 1995.
16. Kofoed H. Thoracic Outlet Syndrome: Diagnostic Evaluation by Analgesic Cervical Disk Puncture. Clinical Orthopedics & Related Research, 1981;156:145-48.
17. LaBan MM, Ed. Physiatric Pearls, Physical Medicine and Rehabilitation Clinics of North America, 1996;7:3.
18. Matsumoto S. Thermographic Assessments of Sympathetic Blockade by Stellate Ganglion Block, Japanese Journal of Anesthesiology, 1991;40(5):692-701.
19. Netter FH. Atlas of Human Anatomy, Third Edition, Elsevier Health Sciences, West Cadwell, NJ, 2002.
20. Ochoa JL. The Human Sensory Unit and Pain: New Concepts, Syndromes and Tests, Muscle and Nerve, 1993;16(10):1009-16.
21. Palmer J, Uematsu S, Jankel W, and Perry A. A Cellist With Arm Pain: Thermal Asymmetry in Scalene Anticus Syndrome. Archives of Physical Medicine & Rehabilitation, 1991;72:237-42.
22. Pećina MM, Krmpotić-Nemanić J, and Markiewitz AD. Tunnel Syndromes, CRC Press, New York, 2001.
23. Raj PP, Ed. Pain Medicine: A Comprehensive Review, Second Edition. Mosby, St. Louis, 2003.
24. Roberts W. Adrenergic Mediation of Sympathetically Mediated Pain Via Nociceptive or Non-Nociceptive Afferents or Both? APS Journal, 1992;1(1):12-15.
25. Schwartz R. Electric Sympathetic Block: Current Theoretical Concepts and Clinical Results. Journal of Back and Musculoskeletal Rehabilitation, 1998;10:31-46.
26. Schwartz, RG. Resolving Complex Pain, Color Edition, Piedmont Physical Medicine & Rehabilitation, Greenville, SC, 2006, p. 104.
27. Schwartz, RG. Resolving Complex Pain, Color Edition, Piedmont Physical Medicine & Rehabilitation, Greenville, SC, 2006, p. 97. Chapter 5 Infrared Thermographic V 46 asomotor Mapping
28. Schwartz, RG. Resolving Complex Pain, Color Edition, Piedmont Physical Medicine & Rehabilitation, Greenville, SC, 2006, pp. 223-30, 233-6, 245-6.
29. Taylor GI and Palmer JH. The Vascular Territories (Angiosomes) of the Body: Experimental Study and Clinical Applications. British Journal of Plastic Surgery, 1987;40:113-41.
30. Waldman SD, Ed. Atlas of Uncommon Pain Syndromes, W. B. Saunders, Philadelphia, 2003.
31. Wasner G, Schattschneider J, and Baron R. Skin Temperature Side Differences – A Diagnostic Tool For CRPS. Pain, 2002;98:19-26.
32. Wilson PR, Stanton-Hicks M, and Harden RN, Eds. CRPS: Current Diagnosis and Therapy, IASP Press, Seattle, 2005.
Francis Sahngun Nahm, MD
Since BC 400 when Hippocrates used temperature in a diagnosis by applying mud to a patient’s body and speculating that dry areas had disease, temperature has been an important area of interest in medicine. The skin is a very important organ in temperature regulation, and body temperature is controlled by the combined control of the central and autonomic nerve system. Infrared thermography (IRT) detects infrared light emitted by the body to visualize changes in body heat due to abnormalities in the surface blood flow of diseased areas. IRT is not a tool that shows anatomical abnormalities, but is a method that shows physiological changes. It objectively visualizes subjective symptoms, therefore, it is useful in making diagnoses and doing evaluations in the field of pain medicine where a diagnosis is based on subjective complaints of symptoms. The advantages of IRT is that it is non-invasive and painless, it is not harmful to the patient, it is possible to conduct tests in a physiologically natural state, and its testing time is short. The aim of this paper is to introduce the basic mechanism of IRT, significance in interpretation, and clinical utilization.
The most important theoretical background of IRT is that the distribution of body heat in a normal body is symmetrical. Therefore, the symmetry of body heat is considered to be the most important element when interpreting IRT images. An infrared camera is used to measure infrared light emitted from the body and displays this on the screen, and pseudocolor mapping is done on the obtained infrared image to facilitate visual interpretation. Therefore, when comparing the distribution of body heat on both sides of the body, the region of interest (ROI) is set to an equal size on each side of the obtained pseudocolor image, and the mean temperature within each ROI is calculated to compare the difference. There are two methods to compare the temperature difference within an ROI of the affected and unaffected sides. The first method is to define a significant difference such as when the asymmetry of temperature deviates from 1-standard deviation of the unaffected side ROI, and second is to define the significance such as when the difference in mean temperature of both ROIs is more than the ‘reference temperature difference’. The latter method is mainly used in the clinical field.
UTILIZATION OF IRT IN PAIN MEDICINE
After Galileo designed the first thermometer in 1592, infrared light was discovered by William Herschel in 1800, and the first diagnostic IRT was used in diagnosis of breast cancer by Lawson in 1956. Then, in 1982, the US Food and Drug Administration approved IRT as an adjunctive screening tool of breast cancer, and up to now, there have been many studies regarding the usefulness of IRT in various areas such as complex regional pain syndrome (CRPS), postherpetic neuralgia, whiplash injury, inflammatory arthritis, temporo-mandibular joint disorder, headache, and myofascial pain syndrome. The diseases where IRT can be used are presented in. Considering that IRT visualizes physiological and functional abnormalities rather than anatomical abnormalities, there is no doubt that compared to other imaging diagnostic methods, IRT is an effective diagnostic method for diseases difficult to diagnose with CT or MRI, such as CRPS, neuropathic pain, headache, and myofascial pain. In fact, for CRPS, it is known to have higher sensitivity compared to MRI or three phase bone scan, and it is reported that thermography has higher sensitivity in diagnosis of neuropathic pain compared to the sympathetic skin response test. When deciding an abnormality in specific diseases, there are different views on what the ‘reference temperature difference’ should be according to researcher, and for CRPS, standards such as 0.6℃ and 1.0℃ are used. Meanwhile, regarding the reliability of IRT, research has been conducted for CRPS and myofascial pain syndrome, and it was reported that there is high reliability for these diseases. In terms of correlation between pain and temperature difference measured with IRT, it was reported that there was a significant correlation between the severity of pain caused by lumbar disc herniation with the difference in skin temperature. It was also reported that there was a significant correlation between the pressure pain threshold and the temperature difference in myofascial pain syndrome. Recently, the technique, which obtains a dynamic image using a stress loading test as well as static IRT, is widely used. The theoretical basis for this is that normally the temperature change on both sides of the body after stress loading is symmetrical, and the degree of temperature restoration after removing the stress is symmetrical on both sides. Therefore, when restoration of temperature is asymmetrical after removal of stress, it is considered that physiological abnormalities exist. For the stress loading test, cold/warm stress, exercise, pharmacological stress, vibration, and visual stimulation are used as stress, and from these, the cold stress test is used the most. When using cold stress thermography, it is known that sensitivity and specificity is enhanced for diagnosis of CRPS, but it causes pain for the patient during the cold stress thermography, and a standardized guideline for the stress loading test has not been established.
POSSIBILITY OF ERROR IN COMPARING THE TEMPERATURE DIFFERENCE OF BOTH SIDES ACCORDING TO THE ROI SETTING
Currently there are no established standards for setting an appropriate ROI. The ROI is set as symmetrical on the pseudocolor image based on the discretion of the examiner taking into consideration the medical history and symptom area of the patient. Therefore, according to the size and shape of the ROI, the temperature difference on both sides can be calculated differently. In addition, the IRT equipment currently used only shows the mean temperature and standard deviation within the fixed ROI, and the actual interpretation of the IRT image only compares the mean temperature of the ROI without considering the size of the ROI. In principle, when comparing two means, statistical difference is determined by considering the mean, standard deviation, and sample size. Thus, when only the mean values are simply compared without considering all these items, there is the possibility of error based on statistical interpretation. Therefore, considering the number of pixels in the fixed ROI (reflecting sample size), and the mean and standard deviation of the temperature in interpreting results can reduce false positives and false negatives, and enable objective interpretation of the results. For this, an ROI of equal size symmetrical for both sides of the body is set, and the t-test can be used taking into consideration the mean temperature, standard deviation, and number of pixels in the ROI, or the pixels on each side can be matched 1:1 to conduct a paired t-test for the temperature difference in each matched pixel. Based on personal opinion, it is difficult to satisfy the assumption that the left and right side of the body are independent; thus, using the paired t-test with matched pixels is thought to be a more valid method statistically. However, there is no testing equipment which provides this kind of function presently. Hence, it is anticipated that an IRT system will be developed to enable such statistical analysis in the future.
DEVELOPMENT OF IRT TECHNOLOGY
Recently, there has been much effort to improve the hardware and software of medical IRT. Developments have been achieved such as enhanced performance of the infrared sensor, improved image quality, real-time image processing, and a multi-channel system. As a result, it is possible to obtain precise images with a thermal resolution of 0.08℃ or lower and a special resolution of 1×1 mm or lower. A 3-dimensional image technique was also developed to show the body heat in a more detailed image compared to the existing 2-dimensional image. In addition, recently a remote diagnosis system was established to decipher images from a long distance away.
IRT is a non-invasive and safe diagnostic method which visualizes functional abnormalities and is used effectively in the diagnosis of numerous diseases and in the evaluation of treatment effect. Compared to other imaging diagnostic methods, it shows high diagnostic performance in pain diseases, and even higher sensitivity and specificity is obtained when using the stress loading test. Together with the development in medical technology, it is anticipated that the use of IRT will gradually increase in the field of pain medicine.
- Uematsu S, Edwin DH, Jankel WR, Kozikowski J, Trattner M. Quantification of thermal asymmetry. Part 1: normal values and reproducibility. J Neurosurg. 1988;69:552–555. [PubMed]
- Szekely V, Rencz M. Image processing procedures for the thermal measurements. IEEE Trans Compon Packaging Technol. 1999;22:259–265.
- Uematsu S, Jankel WR, Edwin DH, Kim W, Kozikowski J, Rosenbaum A, et al. Quantification of thermal asymmetry. Part 2: application in low-back pain and sciatica. J Neurosurg. 1988;69:556–561.[PubMed]
- Lawson R. Implications of surface temperatures in the diagnosis of breast cancer. Can Med Assoc J.1956;75:309–311. [PMC free article] [PubMed]
- Schürmann M, Zaspel J, Löhr P, Wizgall I, Tutic M, Manthey N, et al. Imaging in early posttraumatic complex regional pain syndrome: a comparison of diagnostic methods. Clin J Pain. 2007;23:449–457.[PubMed]
- Nahm FS, Lee PB, Park SY, Kim YC, Lee SC. Comparison of the diagnostic validity of real and absolute skin temperature differences for complex regional pain syndrome. Korean J Pain. 2009;22:146–150.
- Choi E, Lee PB, Nahm FS. Interexaminer reliability of infrared thermography for the diagnosis of complex regional pain syndrome. Skin Res Technol. 2013;19:189–193. [PubMed]
- Han SS, Jung CH, Lee SC, Jung HJ, Kim YH. Does skin temperature difference as measured by infrared thermography within 6 months of acute herpes zoster infection correlate with pain level? Skin Res Technol.2010;16:198–201. [PubMed]
- Paeng SH, Jung YT, Pyo SY, Kim MS, Jeong YG. Is the use of digital infrared thermal imaging useful in whiplash injury? Korean J Spine. 2009;6:274–279.
- Kim SW, Lee SM, Jeong SH. Validation of thermography in the diagnosis of acute cervical sprain. J Korean Neurosurg Soc. 2004;36:297–301.
- Denoble AE, Hall N, Pieper CF, Kraus VB. Patellar skin surface temperature by thermography reflects knee osteoarthritis severity. Clin Med Insights Arthritis Musculoskelet Disord. 2010;3:69–75.[PMC free article] [PubMed]
- Brenner M, Braun C, Oster M, Gulko PS. Thermal signature analysis as a novel method for evaluating inflammatory arthritis activity. Ann Rheum Dis. 2006;65:306–311. [PMC free article] [PubMed]
- Nahm FS, Koo MS, Kim YH, Suh JH, Shin HY, Choi YM, et al. Infrared thermography in the assessment of temporomandibular joint dysorder. Korean J Pain. 2007;20:163–168.
- Gratt BM, Sickles EA, Ross JB, Wexler CE, Gornbein JA. Thermographic assessment of craniomandibular disorders: diagnostic interpretation versus temperature measurement analysis. J Orofac Pain. 1994;8:278–288. [PubMed]
- Ford RG, Ford KT. Thermography in the diagnosis of headache. Semin Neurol. 1997;17:343–349.[PubMed]
- Dalla Volta G, Anzola GP, DiMonda V. The disappearance of the “cold patch” in recovered migraine patients: thermographic findings. Headache. 1991;31:305–309. [PubMed]
- Costa AC, Dibai Filho AV, Packer AC, Rodrigues-Bigaton D. Intra and inter-rater reliability of infrared image analysis of masticatory and upper trapezius muscles in women with and without temporomandibular disorder. Rev Bras Fisioter. 2013;17:24–31. [PubMed]
- Haddad DS, Brioschi ML, Arita ES. Thermographic and clinical correlation of myofascial trigger points in the masticatory muscles. Dentomaxillofac Radiol. 2012;41:621–629. [PMC free article] [PubMed]
- Park SH, Lee PB, Lim YH, Lee SY, Choi IY, Lee SJ, et al. The usefulness of three-phase bone scan and thermography for making the diagnosis of CRPS-I. Korean J Pain. 2006;19:81–86.
- Park ES, Park CI, Jung KI, Chun S. Comparison of sympathetic skin response and digital infrared thermographic imaging in peripheral neuropathy. Yonsei Med J. 1994;35:429–437. [PubMed]
- Bruehl S, Lubenow TR, Nath H, Ivankovich O. Validation of thermography in the diagnosis of reflex sympathetic dystrophy. Clin J Pain. 1996;12:316–325. [PubMed]
- Harden RN, Bruehl S, Stanton-Hicks M, Wilson PR. Proposed new diagnostic criteria for complex regional pain syndrome. Pain Med. 2007;8:326–331. [PubMed]
- McCoy M, Campbell I, Stone P, Fedorchuk C, Wijayawardana S, Easley K. Intra-examiner and inter-examiner reproducibility of paraspinal thermography. PLoS One. 2011;6:e16535. [PMC free article][PubMed]
- Zhang HY, Chin DK, Cho YE, Kim YS. Correlation between pain scale and infrared thermogram in lumbar disc herniations. J Korean Neurosurg Soc. 1999;28:253–258.
- Gulevich SJ, Conwell TD, Lane J, Lockwood B, Schwettmann RS, Rosenberg N, et al. Stress infrared telethermography is useful in the diagnosis of complex regional pain syndrome, type I (formerly reflex sympathetic dystrophy) Clin J Pain. 1997;13:50–59. [PubMed]
- Wasner G, Schattschneider J, Baron R. Skin temperature side differences–a diagnostic tool for CRPS?Pain. 2002;98:19–26. [PubMed]
- Park EJ, Han KR, Chae YJ, Jeong WH, Kim C. Effectiveness of cold stress thermography in the diagnosis of complex regional pain syndrome type 1. Korean J Pain. 2006;19:159–163.
- Nahm FS. Comparing the temperature difference of regions of interest; statistical interpretation. J Korean Soc Thermol. 2009;9:5–9.
- Spalding SJ, Kwoh CK, Boudreau R, Enama J, Lunich J, Huber D, et al. Three-dimensional and thermal surface imaging produces reliable measures of joint shape and temperature: a potential tool for quantifying arthritis. Arthritis Res Ther. 2008;10:R10. [PMC free article] [PubMed]
Neundorfer B, Handwerker HO; Neurologische Klinik, Lang E, Claus D, Friedrich-Alexander-Universitat
Pain intensity in carpal tunnel syndrome (CTS) was correlated with neuro and psychophysiological parameters related to the function of different nerve fiber classes within the median nerve in 23 patients. Control data were obtained from 16 normal subjects. Mean intensity of all pain attacks which occurred 14 days before surgical treatment was assessed on visual analogue scales (average CTS pain). Functions of thick myelinated nerve fibers were determined by motor and sensory nerve conduction studies. Functions of thin myelinated and unmyelinated nerve fibers were evaluated by measuring thresholds of warmth, cold and heat pain on the index and little finger. Pain intensity and neurogenic vasodilatation following noxious mechano-stimulation on the interdigital web between index and middle finger provided additional information on the functioning of nociceptive nerve fibers. Sympathetic reflexes induced by these painful stimuli were assessed by means of infrared thermography and photoplethysmography. Mean intensity of pain attacks (40 +/- 19% VAS) correlated significantly with latency (r = 0.58, P < 0.01) and amplitude (r = -0.50, P < 0.01) of the compound action potential from abductor pollicis brevis muscle following distal median nerve stimulation. Thresholds of warmth, cold and heat pain on index finger were significantly increased during CTS when compared to the control subjects. The magnitude of neurogenic vasodilatation and sympathetic vasoconstrictor reflexes were not significantly different. Average CTS pain correlated inversely to the threshold of heat pain on index (r = -0.46, P < 0.05), but also on the little finger (r = -0.41, P < 0.05), which is not innervated by the median nerve.
Shawli Bardhan1, Mrinal Kanti Bhowmik1, Satyabrata Nath2, Debotosh Bhattacharjee3 1Department of Computer Science and Engineering, Tripura University (A Central University), Suryamaninagar-799022, Tripura 2Physical Medicine and Rehabilitation (PMR) Department, Agartala Government Medical College (AGMC), Agartala-799006 3Department of Computer Science and Engineering, Jadavpur University, Kolkata-700032, West Bengal
firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Temperature difference in the skin surface reflects the abnormality present in the human body. Considering the phenomenon, detection and forecasting the change of temperature is the principal objective of using Medical Infrared Thermography (MIT) as a diagnostic tool for inflammatory pain diseases. Medical Infrared Thermography (MIT) is a noninvasive, non-contact and fast imaging technique that record and monitor the flow of body temperature by receiving the infrared emitted from the skin surface. Based on the standardization of thermogram acquisition and processing techniques and by the adoption of advanced infrared cameras, presently it is feasible to detect the minor temperature difference of the skin surface in the high-resolution infrared images. Recently, the research on inflammatory pain detection using medical infrared thermography concentrated on the area of temperature and statistical analysis based automated detection of abnormality from the thermograms. The paper introduces a significant review focusing on the area of different inflammatory pain detection using infrared thermography along with the environmental condition, protocol selection, and acquisition system specification in summarized tabular format. Based on the rigorous study of the publications in the area of inflammatory pain thermography, the paper also explores the area of thermogram processing and analysis of pain in a review work format.
Human body distribution of temperature is widely affected by pathological abnormalities. Hence the recording of inflammation of the skin surface related with the core temperature distribution can provide essential information regarding the underlying physiological activities. The dissipation of inflammation from the skin surface is radiating in nature and lies in the infrared spectrum of light . The spectrum range of inflammation makes the infrared detector suitable for recording and analysis of the thermoregulatory distribution of the skin. Medical Infrared Thermography is a non-invasive imaging technique that can detect abnormality by allocating and quantifying the inflammatory changes in the skin surface related to the temperature distribution. Since 1987, it has been accepted as a diagnostic imaging technique by the American Medical Association Council and also recently approved by American Academy of Medical Infrared Imaging for medical imaging . The detection method of the Medical Infrared Thermography is primarily based on the evaluation of temperature distribution among contralateral parts of the body. In case of healthy subjects the difference in temperature distribution is not higher than 0.5-degree Celsius . Starting from the last eighties, detection of pain using thermal imaging was examined in many past investigations. Most of the investigations provide statistical quantification techniques for the abnormality analysis. Based on the study of the most relevant works published in the past, the paper represents a review work on pain detection using Medical Infrared Thermography along with the survey of acquisition conditions.
In the rest of the paper, the section II describes some inflammatory pains that can be detected using Medical Infrared thermography. Section III contains the methodological review work related to the pain thermography. The section IV and V represent the review work related to protocol selection for thermogram acquisition, thermal camera specification and disease related thermogram description in descriptive and tabular format. Finally the conclusion along with future work is made in section VI followed by the acknowledgement and the reference part.
II. MEDICAL INFRARED THERMOGRAPHY IN INFLAMMATORY PAIN DETECTION
Temperature distribution analysis and early detection of abnormality due to inflammatory pain are recognizable by Medical Infrared Thermography. Thermographic detections are compared with the clinical observations and tests for possible confirmations. Although the technique heavily depends on the surrounding and background environment, there are a number of reasons for accepting the technique for diagnosis of inflammatory pain. In general, inflammation is related to pain diseases like arthritis, frozen shoulder, Prolapse Intervertebral Disc (PIVD), spondylosis, etc. which are not defense system begins attacking the healthy tissues instead of detected by clinical observations. In case of arthritis, the immune system of the body become affected and the body foreign substances, and it causes inflammation, pain and joint damage. The presence of additional inflammation due to arthritis can be detected using medical infrared thermography.
In frozen shoulder also, pain and restriction of movement arises due to inflammation. The capsule in the shoulder area has ligament and holds the bones of the shoulder with each other. The inflammation in capsule area restricts the movement of joints and generates pain that can be early detected by the thermal imaging. The inflammation due to Prolapse Inter Vertebral Disc (PIVD) pain can generate neuronal activity along with swelling in compression of a nerve in the intervertebral region. Detection and treatment of inflammation using thermography in the initial stage can avoid the nerve compression stage in the human body.
III. METHODOLOGICAL REVIEW OF PAIN THERMOGRAM ANALYSIS
The skin of the human body contributes an important part in thermoregulation by preserving or dissipating heat. The infrared thermal imaging or the clinical thermography reports the distribution of temperature in human skin by receiving infrared radiation from the surface of the human body , . In the past years, authors had detected the abnormality in a human body based on the analysis of temperature distribution and correlated intensity distribution of thermograms. In 1995, Kim et al.  analyzed the thermal difference to detect the lumbar disc herniation. For this purpose, the severity of pain was measured by Visual Analog Scale (VAS) and Graphic Rating Scale (GRS) and compared with the thermal difference to differentiate and detect acute and chronic disc herniation and its level. The thermal difference that they measured for acute and chronic disc herniation was based on the degree of pain, duration of clinical symptom, comparison with clinical signs, types of herniation according to radiological study and based on level of herniation like mild, moderate and severity of pain and compare with the radiological studies like CT Scan, MRI etc. In the year 1997, Hooshmand, H  also detected abnormality in the whole body related to pain using the temperature analysis method. The analysis had been performed on the control volunteers group and neuropathic pain patients. The method was based on the concept that unmyelinated perivascular sympathetic small c-fibers are the origin of neuropathic pain. As because the c-fibers are too small so that they are best evaluated with infrared thermal imaging compared with EMG/NCV or MRI or CT. After analysis, the rate of true positive was 78% and false positive detected 14%.
To analyze pain in the human body using thermal images, Herry et al.  suggested a computer aided decision support technique and summarized the result of the analysis in the year 2002. This technique was the combination of image processing and temperature analysis method. In this technique, in the first step, to remove noise from thermal images , they had followed Poisson distribution and removed noise using Wavelet-based removal technique proposed by Nowak and Baraniuk. Then edge detection and morphological operations were adopted for classification of a body part from the image. In the next step, analysis of abnormal high or low temperature areas was performed by statistical analysis and comparison of intensity distributions of symmetrical or comparable regions of interest and the result is summarized in a computer aided decision support scheme.
Again in the year 2003, Frize et al.  reported a technique based on thermal pattern analysis to detect physiological disorder caused by pain in the human body. The technique was focused on the thermal pattern analysis of normal subjects and abnormal subjects related to pain. For denoising, the thermal images they again followed wavelet-based noise removal technique. To improve the efficiency of images,they removed the undesirable portion of the image. Then to detect the region of interest, classical grid of polygon and isothermal representation of images were used. In the output of image rocessing steps, the statistical analysis was performed to detect an abnormality.
Subsequently to detect Rheumatoid Arthritis (RA) Frize et al.  proposed a temperature measurement based statistical analysis method in the year 2011. This analysis was performed on a normal group of persons with no rheumatoid arthritis and a group of patients suffering from rheumatoid arthritis. In the first step of the analysis, the difference between the average temperature of joints in the control group and the patient group was determined. In the next step, the identification of joints was performed which gives the best confirmation of the presence of Rheumatoid Arthritis based on the temperature difference. In the last step, statistical analysis was performed to find out the significant statistical difference of temperature of joints in the control group and the patient group. The statistical features used for the analysis was skewness, kurtosis, variance, mode/max, median/max, min/max, maxmin, (mode-mean)2,mode/min, median/min and mean/min.
For shoulder impingement analysis, Park et al.  also used statistical analysis method to analyze the temperature distribution of related thermograms. The thermography screening was applied to the region of interest of both the control group and patient group. The statistical analysis of thermogram was performed by SPSS 13.0 using the independent t-test for comparison of each Region Of Interest of patient group and control group. The clinical symptoms, physical examination findings and the thermographic findings are compared by 1- way analysis of variance with a Bonferroni post hoc test on numeric data and Pearson x2 analysis for the binomial data. Pearson linear correlation was performed to find the correlation between the clinical and thermographic data. Clinical abnormality was determined based on the finding of asymmetrical distribution of temperature in between the contralateral body parts.
In 2008, Lee, Junghoon, et al.  proposed a technique for automatic detection of suspicious pain regions on digital infrared thermal images based on SOFES (Survival of the Fitness kind of the Evolution Strategy) algorithm. The suspicious pain region can be detected by using multimodal function optimization algorithm, such as SOFES algorithm  based on the concept that the painful region represents a low temperature or high temperature compared with its neighbor regions on one’s skin in thermography. The preprocessing steps that were required before applying SOFES algorithm are Region of Interest (ROI) detection, FPA sensor’s output signal extraction and applying Gaussian to blur the image.
In 2010,Tkacova, M., et al. performed infrared thermography analysis in a group of patients suffering from carpal tunnel syndrome. The analysis was based on the asymmetry factor calculation using the histogram of the temperature distribution of contralateral hand parts. To determine the asymmetry factor, the authors used the method explained by Huygen et al. in the year 1998. The authors Zivcak, J., et al [15.]extended their work in the year 2011 by applying statistical features in the large no. of thermogram to calculate the asymmetry of temperature distribution. The temperature analysis was performed in 5 points of the dorsal side of the hand. The analysis indicates that the temperature distribution of the median nerve in the dorsal hand side was significantly different between the control group and carpal tunnel syndrome group. The analysis shows 0,714 sensitivity with 0,714±0, 1207 confidence interval and 0,852 specificity with 0,852±0,095 of confidence interval.
In 2011, Borojevic, N., et al. [16.] also analyzed the thermogram of rheumatoid arthritis and osteoarthritis in human hand. The basic statistical analysis of temperature was performed. The asymmetry of temperature distribution was measured using 4 ways ANOVA test in between the ventral and dorsal side of hand of healthy and arthritis subjects. The mean value showed the best significant difference between the two subjects (healthy and arthritis subjects).
The heat distribution related to rheumatoid arthritis was again evaluated by Snekhalatha, U., et al. in 2012 depending on the heat distribution index. The authors also segment the region of interest using fuzzy c means and Expectation Maximization algorithm. From the analysis, they predicted an abrupt temperature variation in the affected due to rheumatoid arthritis.
IV. SURVEY ON IMAGE ACQUISITION PROTOCOLS
For thermal imaging related to pain, there is no protocol that is universally accepted as acquisition standard at present. For this reason, each clinic or university or research group follows their own protocol as per their needs. But there is a similarity found in the acquisition condition of patients, room temperature, and other different factors. Frize et al.  recommended the thermography at 20°C room temperature. They instructed their patients, not to apply talcum powder, lotion or deodorant on skin on the day of examination. Some controllable factors such as hot drinks, alcohol, physical exercise, etc. could potentially produce effect on the skin. For this purpose, they recommended not to take hot drinks one hour prior to the imaging, not to smoke two hours prior to the examination and to avoid prolonged sun exposure for a week before imaging. Also they suggested avoidance of alcohol twelve hours prior to the imaging and also avoidance of acupuncture, hot or cold presses, physiotherapy, TENS (Transcutaneous Electrical Nerve Stimulation) and physical exercise twenty-four hours prior of the session. According to Park et al. room temperature needs to be set on 19 to 20°C and patients need to be in upper body disrobed condition 15 minutes before the screening to get a stabilized condition. Lee, Junghoon, et al. recommended their patients not to apply any lotion or ointments and also to put off rings, necklaces, and watches. They also recommended that patients should quit physical therapies. According to their preparation for thermography, in order to be stabilized, patients should keep themselves undressed for more than 20 minutes before imaging. Tkacova, M., et al and Zivcak, J., et al  also suggested to keep the region of interest for thermography in undressed condition for 20 minutes before capturing of thermogram at 20°C . The room for thermography was retracted blind from solar radiation. Borojevic, N., et al. performed their acquisition in a stable condition of temperature and humidity. Snekhalatha, U., et al also recommended to perform the capturing in a stable temperature of 20°C with 20 minutes stabilization of patients in disrobed condition at the area of imaging.
V. SURVEY ON THERMAL CAMERA AND THERMOGRAMS
Kim et al.  analyzed thermography related to lumbar disc herniation of 147 patients and grouped them into acute and chronic based on severity of pain which was measured by Visual Analog Scale (VAS) and Graphic Rating Scale(GRS). The number of cases related to acute disc herniation was 78 and 69 were present in chronic disc herniation. The thermography camera used by the author was Digital Infrared Thermographic Imaging (D.I.T.I. DOREX Inc) for evaluation of pain based on thermograms. Hooshmand, H  studied the thermography related to neuropathic pain in the human body using Agema Cameras with Bales Scientific Thermal Processor. For this purpose, 682 thermograms of neuropathic pain patients and 100 thermograms of control volunteers had been taken for the study. Herry et al.  considers 100 patients from the Pain Clinic of the Moncton Hospital, New Brunswick, Canada in between the year 1981 and 1984 by using a thermal camera of 128×128 pixels with 256 gray intensities level named as AGA Thermovision 680 medical ans AGA OSCAR. Frize et al.  captured the first set of 100 thermograms related to pain in the human body from Pain Clinic of the Moncton Hospital, New Brunswick, Canada, between 1981 and 1984. The second set of 24 thermograms related to normal healthy volunteers had been taken in the year June 2002 for comparison and analysis with thermograms related to pain. All the thermograms were of the back and legs of the human body. Frize et al.  used a thermal camera of 320×240 pixels to analyze the thermograms of patients suffering from Rheumatoid Arthritis. They had taken thermograms of 13 patients and 18 normal subjects, and those images were collected from knees, wrists, palms and from joints of hand. Among those 13 patients, 9 were female, and 4 were male and out of 18 normal subjects 8 were female and 10 were male. The wavelength of the thermal camera was from 7.5 to 13 μm, and Field of View (FOV) was 24°x18° with 1.3 mrad spatial resolution and 0.05°C at 30°C thermal resolution. The minimum focus distance was 30 cm, and the imaging speed was 30 frame/sec. Park et al.  present a research related to the thermographic imaging in patients with shoulder impingement syndrome. This was performed by using the IRIS5000 (Medicore, Seoul, Korea) and consisted of a computer, an infrared camera and a liquid crystal display monitor. Thermograms of upper body of 100 selected patients in 4 views were taken from shoulder and elbow joints at the clinic in the Department of Orthopaedic Surgery. The four views were posterior, anterior, left and right lateral views and, among those 100 patients, 55 were men, and 45 were women. They had also taken 30 thermograms of the same four views from normal persons without any pain or problem to study the thermography related to shoulder impingement. Lee, Junghoon et al.  collected thermograms of patients suffering from glycosuria, degenerative arthritis and varicose vein using a Thermal Vision of MESH Co., Inc. in Republic of Korea. The images were of size 320×240 pixels, and the thermal sensitivity of the camera was less than 50 mk. For analysis, Tkacova, M., et al  collected 7 thermograms related with carpal tunnel syndrome patients and also collected 7 symmetrical thermograms of healthy persons using ThermaCam Fluke Ti55/20 acquisition system. with thermal sensitivity 0.05°C at 30°C and resolution 320×240 pixels. The
spectral range of the camera was 8 to14 μm. The dorsal view of the hand was taken parallel at the distance of 0.55 meter and in extended analysis, Zivcak, J., et al  had taken total 268 thermograms of dorsal hand side of both the healthy patients and pathological hands containing Carpal Tunnel Syndrome with 0.98 thermal camera emissivity. Borojevic, N., et al  captured ventral and dorsal side of hand using Thermo Tracer TH7102WL system. Their analysis was performed on the thermograms of 6 healthy volunteers, 8 patients containing rheumatoid arthritis and 7 patients of osteoarthritis. Snekhalatha, U., et al.  also captured thermogram of anterior and posterior view of hand for rheumatoid arthritis using ThermaCAMT400 camera from 1-meter distance of the region of interest. The thermograms was taken from 10 patients with rheumatoid arthritis and for analysis thermogram of 10 normal persons are also taken and analyzed. The Table III represents summary of camera specification and details of thermogram and disease in tabular form.
VI. CONCLUSION AND FUTURE WORK
With the advent of high sensitivity infrared cameras, Medical Infrared Thermography is becoming an alternative diagnostic tool for inflammatory pain detection. In addition to high sensitivity, thermogram resolution and accuracy, infrared thermography is a non-invasive methodology with harmless imaging technology. The thermograms are stored digitally for further analysis using various software packages and image processing based analysis to obtain the pattern of temperature distribution. In this paper, the methodological review briefly describes the analytical methods of pain thermograms. Studies so far indicate that, the statistical analysis of temperature distribution of thermogram is common and widely accepted method for abnormality analysis related to inflammatory pain. The review based study also shows that, the control environmental condition and proper protocol selection for minimum interference are effective parts of the accurate thermogram acquisition. But there is no protocol that is universally accepted for inflammatory pain analysis a present. In the future phase, the work will be extended by creation and analysis of database related to inflammatory pain in the human body by following required standardized protocols of thermogram acquisition.
The work presented here is being conducted in the Bio-Medical Infrared Image Processing Laboratory (B-MIRD), Department of Computer Science and Engineering, Tripura University (A Central University), Suryamaninagar-799022, Tripura(W). The research work was supported by the Grant No.BT/533/NE/TBP/2013, Dated 03/03/2014 from the Department of Biotechnology(DBT), Government of India. The first and second author would like to thank hon’ble Vice Chancellor Professor Anjan Kumar Ghosh, Tripura University (A Central University) and Professor Barin Kumar De, Department of Physics, Tripura University (A Central University) for their kind support to carry out this work.
 S. Bagavathiappan, et al., “Infrared thermal imaging for detection of peripheral vascular disorders,” Journal of medical physics/Association of Medical Physicists of India, vol. 34(1), 2009, pp. 43–47.
 C. Hildebrandt, C. Raschner, and K. Ammer, “An overview of recent application of medical infrared thermography in sports medicine in Austria.” Sensors 10(5), 2010, pp 4700-4715.
 RA. Freitas., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999.
 C. L. Heny, and M. Frize, “Digital Processing Techniques For The Assessment OF Pain With Infrared Thermal Imaging”, Proceedings of the Second Joint EMBS/BMES Conference Houston, TX, USA, October 23- 26, 2002, pp.1157-1158.
 M. Frize, et al., “Detection of rheumatoid arthritis using infrared imaging”, Proceedings of SPIE Medical Imaging, International Society for Optics and Photonics, 2011, pp. 79620M-79620M.
 Y. Kim, and Y. Cho, “Correlation of pain severity with thermography,” IEEE 17th Annual Conference In the Engineering in Medicine and Biology Society, vol. 2, 1995, pp. 1699-1700.
 H. Hooshmand, “The role of IR thermography in diagnosis and management of pain,” Proceedings of the IEEE 19th Annual International Conference. In Engineering in Medicine and Biology Society., vol. 2, 1997, pp.625 -630.
 R.D. Nowak, and R.G. Baraniuk,. “Wavelet-domain filtering for photon imaging systems,”. Image Processing, IEEE Transactions on Image Processing , vol. 8(5), 1999, pp.666-678.
 M. Frize, C. Herry, and N. Scales,.“Processing thermal images to detect breast cancer and assess pain,” Proceedings of the 4th Annual IEEE Conference On Information Technology Application In Biomedicine, 2003, pp. 234–237.
 J.Y. Park, J.K. Hyun, and J.B. Seo, “The effectiveness of digital infrared thermographic imaging in patients with shoulder impingement syndrome,” Journal of Shoulder and Elbow Surgery, vol. 16(5), 2007, pp. 548-554.
 J. Lee, et al., “Detection of suspicious pain regions on a digital infrared thermal image using the multimodal function optimization,” 30th Annual International Conference of the IEEE. In Engineering in Medicine and Biology Society, 2008, pp. 4055-4058.
 J. H. Lee, et al., “Multimodal Function Optimization Based on the Survival of the Fitness kind of the Evolution Strategy,” 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2007, pp.3164-3167.
 M. Tkacova, P. Foffova, R. Hudak, J. Svehlik, and J. Zivcak. “Medical thermography application in neuro-vascular deseases diagnostics,” IEEE 8th International Symposium on Applied Machine Intelligence and Informatics (SAMI), 2010, pp. 293-296.
 M. Anbar, and L. Milescu, “Prerequisites of dynamic area telethermometry (DAT),”. Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society; vol. 2, 1998, pp. 928-931.
 J. Zivcak, L. Madarasz, and R. Hudak. “Application of medical thermography in the diagnostics of Carpal Tunnel Syndrome,” 12th International Symposium on. IEEE Computational Intelligence and Informatics (CINTI), 2011, pp. 535-539.
 N. Borojevic, et al., “Thermography of rheumatoid arthritis and osteoarthritis,” Proceedings in ELMAR, 2011, pp. 293-295.
 U. Snekhalatha., et al., “Thermal image analysis and segmentation of hand in evaluation of rheumatoid arthritis,” International Conference on. IEEE Computer Communication and Informatics (ICCCI), 2012, pp. 1-6.