Musculoskeletal & Sports Medicine

 

 

The Application of Medical Infrared Thermography in Sports Medicine

Carolin Hildebrandt1, Karlheinz Zeilberger2,Edward Francis John Ring3 and Christian Raschner1 of
1 University of Innsbruck, Department of Sport Science, Innsbruck
2Medical Practices for Internal and Sports Medicine, Munich
3Medical Imaging Research Group, Faculty of Advanced Technology,
University of Glamorgan
1Austria
2Germany
3UK

 

1. Introduction

Medical Infrared Thermography (MIT) is a non-radiating and contact-free technology to monitor physiological functions related to skin temperature control. The efficiency, safety and low cost of MIT make it a useful auxiliary tool for detecting and locating thermal abnormalities characterized by increases or decreases in skin surface temperature. It has been successfully utilized in the field of veterinary medicine to detect locomotion injuries in racehorses and to monitor their health status. However, research on human athletes with modern infrared sensor technology is more rare. Athletes are exposed to physical stress in training and during competition season. Overuse reactions and so-called “minor traumas” are very frequent; therefore, early detection is critical to avoid injuries. Research suggests that the most beneficial application of MIT is the screening of individuals for overuse injuries. In the following chapters, the use of MIT in clinical practice is presented with special focus on sports injuries and exercise-induced physiological functions. Case studies illustrate the clinical applicability.

 

2. MIT – Quo Vadis?

 

2.1 History and development

The association between changes in temperature and disease is almost as old as medicine itself. Hippocrates stated, “should one part of the body be hotter or colder than the rest, then disease is present in that part”. The first application of thermal imaging was in the early 19th century and did not have any commercial purpose. Following the 2nd World War, infrared imaging systems were used to monitor changes in skin temperature in relation to certain diseases (Ring, 2007). Poor quality imaging systems and a lack of methodological standards in the past has limited quality, resulting in non-acceptance of the technique (Elliot & Head, 1999). Technological advances in infrared cameras within the last few years have promoted MIT as a powerful measurement tool. A new generation of high-resolution cameras, appropriate software and standardized protocols have been developed for medical imaging, resulting in improved diagnostic capability and reliability (Plassmann et al., 2006; Diakides & Bronzino, 2008). In 1987, the American Medical Association recognized MIT as a feasibleThe following worldwide Thermographic organizations promote the proper application of medical thermal imaging.

  • International Academy of Clinical Thermology
  • International Thermographic Society
  • American Academy of Medical Infrared Imaging
  • European Association of Thermology
  • Northern Norwegian Centre for Medical Thermography
  • German Society of Thermography and Regulation Medicine

 

2.2 Technical principles

Most of the diagnostic imaging modalities in medicine utilize portions of the electromagnetic spectrum (Hildebrandt et al., 2010). However, in contrast to other medical devices, MIT uses non-ionising radiation, thus allowing an unconstrained and harmless application in patients. Using infrared radiation, infrared cameras generate thermal images based on the amount of heat dissipated at the surface. Roughly 80% of the emitted infrared radiation of human skin is in the wavelength range of 8-15μm (Steketee, 1973). The technology operates in the long-wave infrared region and is a sophisticated way of receiving electromagnetic radiation and converting it into electrical signals. These signals are finally displayed and matched to colors on the screen for calculations. Modern focal plane array detectors ensure a stable image with high thermal resolution. Sensitivity and resolution are important parameters for medical devices (Plassmann et al., 2006). High-resolution cameras with focal plane arrays of 320×240 pixels, a thermal sensitivity less than 50mK and a spatial resolution of 25-50μm ensure useful thermal and spatial details (Ring & Ammer, 2000). The resulting information can be used to provide instant feedback on the patient or athlete. Unlike other medical imaging modalities, MIT is not related to morphology. However, to study cutaneous circulation, the non-contact method of MIT was compared with other medical imaging modalities. Merla et al. (2007) calculated blood flow by using MIT and laser Doppler imaging (LDI) and showed that cutaneous blood perfusion values obtained from MIT correlate with those obtained by means of LDI and have the advantage of a better time resolution.

 

2.3 Biological principles

Human skin, with an emissivity (an object’s ability to emit radiation) of 0.98, is almost equal to a black body radiator (Steketee, 1973). The physics of heat radiation and the physiology of thermoregulation in the human body make the reliable and valid interpretation of thermal images difficult. Skin temperature regulation is a complex system that depends on blood-flow rate, local structures of subcutaneous tissues and the activity of the sympathetic nervous system (Kellog & Pergola, 2000). However, there is evidence that the sympathetic nervous system is the primary regulator of blood circulation in the skin and is, therefore, the primary regulator of thermal emission (Charkoudian, 2003). Vasoconstriction and vasodilation of the blood vessels function to regulate blood flow in the skin. Thermoreceptors in the skin, also known as Ruffini corpuscles, recognize the ambient temperature. An increased temperature results in vasodilation, leading to increased blood flow to the skin, whereas vasoconstriction occurs by adecrease in temperature and results in reduced blood flow to the skin (Wallin, 1990). These physiological processes combine with heat transfer and thermoregulation in convection, conduction, radiation and sweat evaporation. Heat transfer by radiation is of great value in medicine (Blatteis, 1998). To date, the mechanism of thermoregulatory adaption to exercise is complex and not entirely understood.

 

3. MIT – What is its place in medicine?

 

3.1 Human medicine

MIT is used in a variety of medical applications in the fields of neurology, oncology, orthopedics, and dermatology (Diakides & Bronzino, 2007). The technique has gained widespread use in breast cancer research (Arora et al., 2008; Ng, 2009; Kontos et al., 2011). Tumors are characterized by increased angiogenesis and, therefore, increased metabolic activity, leading to higher temperature gradients compared to surrounding tissue. In addition, MIT is well accepted in surgery. In aortic-coronary bypass surgery, it is possible to monitor the restart of blood flow through the coronary blood vessels (Wild et al., 2003). In plastic surgery, an infrared camera can evaluate the reperfusion of perforator flaps (de Weerd, 2006). For all medical areas, it should be noted that MIT, as an outcome measure, provides a visual map of the skin temperature distribution but cannot quantify absolute temperature values. In addition, MIT alone should not be used as a diagnostic tool; clinical examinations must be included for interpreting thermograms. Several global medical institutions are concerned about scientific work, and the practical application of MIT in medicine has lead to an increased number of publications in peer-reviewed journals.

 

3.2 Sports medicine

MIT has been successfully utilized in the field of veterinary medicine to detect locomotion injuries in racehorses and to monitor their health status (Turner, 2000; Eddy et al., 2001). By using an infrared camera, Turner et al. (2000) examined tendonitis in race horses and detected hot spots before clinical evidence of swelling and lameness. However, research on human athletes is more rare. Sports medicine must provide high-quality care for athletes, and a modern approach for identifying risk factors and injury prevention should be of primary importance (Bruckner & Khan, 2006). Athletes are exposed to great physical stress in training and during competition. Overuse reactions are frequent; therefore, their early detection is important. Furthermore, early detection and localization of inflammation is a critical step in determining the appropriate treatment. Inflammation will usually cause a localized increase in skin temperature, thereby disturbing the “normal” symmetry. Nerve damage or disturbances to the autonomic nervous system may also cause a change and may lead to a localized cooling of the affected area. Because this is a remote sensing technique, it is possible to monitor body surface temperature during and after movement and thereby detect changes in skin temperature caused by the exercise or therapy (Ring & Ammer, 1998, Hardaker et al., 2007). Within the field of sports medicine, long-time sport specific changes in physiology and therefore thermoregulatory processes, as well as changes in anatomy such as muscle structures, needs to be considered.

 

3.3 Standardization methods

Modern state-of-the-art technology has made MIT a reliable measurement tool (Jiang et al., 2005). When used as an outcome measure it must satisfy the basic criteria of measurement. The quality of thermal imaging depends on the technical equipment and the experience of the examiner (Plassmann etal., 2006, Ring & Ammer, 2000). Proper care must be taken with standardization of the imaging procedure to avoid misinterpretation of the thermograms. Thermography societies provide protocols including examination recommendations and technical guidelines. The following aspects are considered:

  • Control of Examination Room Conditions
  • Patient Preparation
  • Number of Studies and Views
  • Equipment
  • Patient Identification
  • Thermogram Analysis

A thermogram represents the human skin temperature profile illustrated by a color spectrum. However, false colors do not necessarily represent a particular temperature. To standardize the analyses of medical thermograms used for fever detection, the International Standards Organization (ISO) recommended the use of the “rainbow” temperature scale that represents high temperatures with red colors and low temperature with blue colors. To visualize differences within similar tissues or structures, the “rainbow strong-contrast” scale can also be used. When focusing on the vascular system, a gray color scale is preferred.

Image fusion, merging the infrared image and a digital image, is another important step for reliable analyses. This technique allows better mapping of anatomical landmarks and therefore provides a precise definition of the region of interest (ROI). Additional labeling of anatomical landmarks within the ROI provides consistency for repeated measurements. To provide a standard for size, shape and placement of the ROI, a research group from the University of Glamorgan has proposed a protocol based on anatomical landmarks (Plassmann & Murawski, 2003; Ammer, 2008).

 

4. Applicability of MIT in clinical and athletic use

Peripheral circulation plays an important role in tissue healing and thermoregulation. To interpret skin temperature changes following injuries (non-thermal stimuli) and exercise (internal stress stimuli), we need to understand the different physiological responses in the structures involved.

 

4.1 Non-thermal stimuli / sport-specific case studies of injuries

The following chapter focuses on case reports of specific sport injuries. Thermal images were taken with a modern infrared camera. Further technical details can be found in the article from Hildebrandt et al. (2010). Normal findings in human body skin temperature are a symmetrical distribution (Vardasca 2008; Selfe et al., 2008), and injury can affect this thermal symmetry. Figure 5 represents an example of a symmetrical temperature distribution of the knees from a healthy subject. On the anterior view the patella appears as a cold shield due to bony structure. The muscles of the upper and lower leg represent hot areas due to high metabolic activity in the muscles. The posterior aspect of the knee shows high temperature in the popliteal fossa because of the popliteal arteries and veins. From a qualitative point of view, side-to-side comparison shows a very symmetrical pattern. To define whether a thermogram is normal, a current project at the University of Glamorgan aimed to create a database of thermal images from different parts of the body from healthy subjects. Previous literature has shown that a difference of more than one degree centigrade between sides of the body may indicate a pathophysiological process (Selfe et al., 2008). However, long-time, observational data from injured and non-injured athletes needs to be investigated to define sports specific thermograms. An injury causes blood flow variations that then affect skin temperature. Many medical conditions are associated with regional vasodilation and constriction, hyperperfusion, hypervascularization and hypermetabolism that cause higher temperature profiles of the skin surface. Physicians need a deeper understanding of the biological nature of thermal signals and consistent thermal alterations of sport specific injuries for early intervention and correct treatment. In addition, the natural healing process of traumatic and overuse injuries can be easily monitored by using thermal imaging. However, this requires the comparison of baseline images prior to and following an injury.

 

4.1.1 Overuse injuries

 

FOOTBALL

High-intensity training combined with frequent competition pushes the locomotor system to its anatomical and physiological limits. Woods et al. (2002) stated that young football players are at a greater risk of minor injuries, overuse injuries, lower leg injuries and muscle strains during the preseason period. We conducted preseason measurements of 25 football players (mean age 17.6± 3.9 years, height 176.1± 8.1 cm, mass 67.8±9.1 kg) from a Football Academy. Fifty two percent of the athletes reported no injuries, 28% had an overuse injury and 20% sustained a traumatic injury within the previous 6 months. The following example shows a non-acute overuse injury of a 17-year old football player. He was diagnosed with recurrent medial shin splint on his left leg and was asymptomatic when the baseline images were taken. However, the area of referred pain on the left leg matches the area of cooler skin along the tibiae. This problem became even more visible following a sport-specific warm up program, indicating a low metabolic activity around the affected structures (Figure 6b). In addition, the athlete had a history of osteochondrosis at the tibial tuberosity of both knees. Especially following exercise, the tibial tuberosity on both knees appeared as a cold area. The following example of a 25-year old professional football player represents an incidental finding. Images were taken within the scope of a team screening. On the injury questionnaire, no acute problems were reported. Upon inquiry no signs of venous disease were reported. However, the subject´s right greater saphenous vein appeared very clearly as an area of increased warmth on the thermogram that may indicate a vascular dilatation with beginning venous insufficiency (Figure 7). Further observational research will determine if this abnormality predict future problems prior to the onset of symptoms.

 

RUNNING

Epidemiological studies have shown an alarmingly high incidence of knee, foot, ankle and lower leg injuries in recreational and competitive runners. Most of these injuries were overuse injuries including stress fractures, shin splints, patellar tendinitis and, most prevalent, Achilles tendinitis (Hreljac, 2005). The following thermograms were taken of a 22-year old competitive middle distance runner who runs 40-100km a week. He reported pain in his right Achilles tendon that occurs gradually, especially during exercise. The athlete was diagnosed with mid-portion Achilles tendinopathy with mild morphological abnormalities. At the time the images were taken, there was a small but noticeable pain at rest and no swelling. The average temperature of the ROI on the right side was 1.6° C lower compared to the non-affected side. The lower temperature may indicate lower metabolic activity due to affected tissue with a loss of normal fiber structure.

Following a treatment period of 8.5 weeks, including electro-physical and physio-therapeutic treatment, thermograms were taken again under resting conditions and following a 45-minute run of low intensity.The side-to-side temperature difference dropped to 0.6°C before exercise, indicating better metabolic activity of the affected side. Following exercise, the right Achilles tendon junction was colder compared to the left one, with a temperature difference of 1.0°C. The athlete reported no pain at rest or following exercise. The regular treatment seemed to improve the Achilles tendon metabolism. However, the impaired metabolic activity following the sport-specific exercise needs to be further addressed with continuing therapy to prevent recurrent problems.

 

SWIMMING

A study, by Sein and co-workers in 2008, investigated shoulder pain in elite swimmers and found that 91% of the swimmers reported shoulder pain; moreover, 84% of the athletes demonstrated a positive impingement sign. The following thermal image was taken of a 27-year-old elite female swimmer under resting conditions (Figure 11). Following a high-volume swimming program, she reported pain and stiffness in both shoulders. With her right arm, she had difficulty reaching behind her back. The clinical examination confirmed overloading of the supraspinatus tendon and general stiffness of the shoulder muscles on both sides. The thermal image shows a hot area above the right deltoid muscle and a hot spot on both shoulders in the region of the humeral head, near the insertion of the supraspinatus muscle. Based on healthy baseline thermal images, MIT should be used to further monitor pathophysiological thermal changes during high-volume swim training prior to the onset of symptoms.

 

YOUTH SPORTS

A common problem, predominantly in young, male athletes is the occurrence of enthesopathy of the ligamentum patellae (Gholve et al., 2007). This insertion tendinitis, caused by repetitive mechanical strain of the patella tendon, is characterized by pain, swelling and tenderness above the tibial tuberosity (Brukner & Khan, 2006). Thermal images clearly show a hyperthermic area above the tibial tuberosity (Figure 12). Long term evaluation of affected athletes from alpine skiing (n= 7), football (n=3), running (n=2) and tennis (n=1), who showed acute symptoms in one leg, revealed a side-to-side temperature difference of 1.1°C (± 0.71 °C). The technique provides a quick screening tool and should be used as a first-line detection tool prior to ultrasound or conventional X-rays.

 

4.1.2 Traumatic injuries

Traumatic injuries usually involve a long, costly rehabilitation period, and they are challenging for the athlete. An injured athlete is under pressure to return to competition as soon as possible. High-quality treatment can reduce the duration and negative impact of the rehabilitation period. It is well known that richly vascularized areas heal faster compared to poorly vascularized areas (Singer et al., 1999). MIT may give information about the state of vascularization and the on-going healing process to ensure the most effective treatment and provide recovery information to decrease the likelihood of re-injury by returning to the sport too quickly.

 

ALPINE SKIING

Knee injuries, especially ruptures of the anterior cruciate ligament (ACL), represent a significant problem in professional alpine skiing (Flørenes et al., 2009) as illustrated by the case of a 21-year-old skier. At 16 years the skier ruptured his left anterior cruciate ligament, medial collateral ligament and the medial meniscus. Since that time, he has suffered from periodic pain, predominantly around the patellae. At age 20 years he was diagnosed with articular cartilage, damage grade three. According to the International Cartilage Repair Society, grade three indicates that the lesion affects more than 50% of the cartilage layer. The average temperature difference of the left patellae was found to be 1.6°C lower compared to the right side. The temperature difference from the area above the upper kneecap showed a side difference of 1.2°C, indicating poor metabolic activity of the lower quadriceps muscle under resting conditions.

 

TRIATHLON

The incidence of tendon ruptures has increased in recreational sport activities, with the highest incidence in older age groups (Clayton et al., 2008). However, Rettig et al. (2005) stated that the potential risk of re-rupture is highest in athletes younger than 30 years of age. The infrared images below were taken of a 26-year old triathlete, 6 months following a complete rupture and direct operation of his right Achilles tendon (Figure 14). When the images were taken, he was referred with mild pain that was exercise dependent and a feeling of numbness in the outer toes. The ongoing healing process did not seem to be sufficiently complete. The temperature difference of an area from the upper Achilles tendon to the muscle belly of the musculus triceps surae was found to be 1.6°C, suggesting delayed healing with impaired circulation. In particular the cooler area of the musculotendinous junction should be considered further within physio-therapeutic treatment.

The area of numbness becomes visible through a clear hypothermia on the affected toes and must be a target of further rehabilitation (Figure 15a,b). Future research will determine if tissue remodeling is still on-going after symptoms disappear.

 

4.1.3 Static versus dynamic measurements

Baseline recordings, following a sport-specific strain, should be conducted to visualize thermal regulatory processes. Regarding infrared images of overuse injuries, repeated measurements following sport-specific exercise will clarify if symptom-free asymmetrical temperature distributions are predictive for presymptomatic identification of initiating overuse reactions. The following example of an 18-year old football player indicates a presymptomatic thermal abnormality during pre-season measurement. The thermogram at rest demonstrated symmetrical patterns. Following sport-specific exercise, local side differences on the knee were visible. The athlete reported no pain at that time.However, during the season, he reported a feeling of load-dependent, diffuse knee pain in his left leg. The medical examination confirmed a low threshold for pressure on the medial aspect of the knee. No clear diagnosis could be confirmed, indicating a local overuse reaction. Excessive stress should be administered with caution.

 

4.2 Thermal stimuli- time sequential images following different exercise

Physical exercise and repetitive strain is a challenge to thermal homeostasis. During exercise, the thermoregulatory control of blood flow in the skin is important to maintain normal body temperature and leads to changes in hemodynamics, and, therefore, thermal signals (Kenney & Johnson, 1991). Using state-of-the art infrared sensor technology, cutaneous temperature changes during exercise can be evaluated. Skin blood flow is predominantly regulated by neural regulation (Thomas & Segal, 2004). By taking time-sequential images of exercise, the immediate response of the sympathetic nervous system via the somatocutaneous reflex can be visualized. The investigation of infrared images taken before and after sport-specific exercise may further determine the applicability of MIT to investigate the physiology of biological tissue. Furthermore systemic cutaneous blood flow regulation can be monitored as a function of exercise type, duration and intensity.

 

AEROBIC VERSUS ANAEROBIC EXERCISE

The mechanism of homeostasis during exercise is guaranteed through multiple functions, such as cardiac processes, peripheral circulatory control, blood pressure regulation and temperature control (Berne & Levy, 2000). A better understanding of the cutaneous circulation, and, therefore, the control of blood flow during exercise is a challenge in integrative physiology (Kellog & Pérgola, 2000). We investigated thermal characteristics of aerobic and anaerobic bicycle exercise to predict evidence of altered perfusion. Twelve athletic males (mean age 26.0 ± 2.7 years, height 177.2cm ± 4.3 cm, mass 71.1 ± 8.4 kg) performed both, anaerobic exercise (5 minutes, 80rpm, 90%HRmax) and aerobic exercise (45 minutes, 80rpm, 60%HRmax) under thermo-neutral conditions. Images were taken prior to (Figure 17a) and immediately following aerobic (Figure 17b) and anaerobic exercise (Figure 17c). The ROI was defined above the middle portion of the M. quadriceps. The temperature above the exercising muscle increased following aerobic exercise (0.7°C, p=0.215) and decreased following anaerobic exercise (- 5°C, p=0.094). In addition hot colored dots over the thigh occurred after aerobic exercise. To meet the increased metabolic demand of active muscles, short- term, intense exercise leads to a redistribution of blood flow away from inactive tissues such as the skin, to exercising muscles through the vasoconstrictor system (Kenney & Johnson, 1991). This process explained the marginal skin temperature decrease following anaerobic exercise. From a clinical point of view, this observation becomes interesting for patients with compromised cardiac function. As previously reported, these patients showed a higher magnitude of vasoconstriction compared to a healthy group, suggesting that the initial reflex vasoconstriction may be linked to cardiovascular functional capacity (Zelis et al., 1969). With continuing exercise, the body core temperature begins to rise. When internal temperature increases toward a threshold, a regulating system starts to stimulate thermo-sensitive neurons in the central nervous system. This triggering of cutaneous vasodilation ensures the transfer of metabolic heat from the core to the skin (Charkoudian, 2003). The present study showed that the competing system of thermoregulatory drive for cutaneous vasodilation and the non-thermoregulatory drive for cutaneous vasoconstriction could be visualized by using MIT. As previously reported, the interactive control system, as a normal function of dynamic muscular exercise, seems to dependent upon the intensity and duration. The multiple hot spots seen on the thigh (Figure 17b) illustrate the so-called perforating blood vessels that originate in deeper lying tissue. The vasoconstrictor mechanism at the beginning of the exercise is mainly in the skin blood vessels, whereas the perforator vessels are less affected. As exercise duration increases, they contribute to the rewarming of the skin (Merla et al., 2010). The identification of a skin thermographic map of perforator vessels that includes their perfusion area can be important to define individual anatomy of certain tissues (Salmon et al., 1988). Further research should examine the time-course of thermal changes by taking multiple images during and following an exercise. In addition, the relationship between thermal changes, aerobic capacity and performance may further determine different functional states of the body dependent on intensity and duration.

 

5. Conclusion

High-quality scientific work with modern 21st-century technology coupled with a better understanding of the regulation of skin blood flow has improved the capability of MIT in medical use. Our research findings suggest that the most beneficial output of MIT seems to be in the screening of athletes for overuse injuries. We suggest combining baseline images with images taken following sport-specific exercise to provoke sufficient thermal alterations in the tissues. A main challenge is to combine the anatomical and physiological information demonstrated by the thermal pattern of the skin. The biological nature of thermal signals and consistent thermal alterations of different sport-specific injuries should be further addressed. Thermal screening of injured and non-injured athletes is the first step to create a sport-specific database with individual thermograms. Repeated follow-up measurements during the sport season will further clarify the link between asymmetrical temperature distributions, pathophysiological changes on the skin surface and the extent of injury. The long-term aim is to create a knowledge-based database of thermograms of overuse and traumatic injuries. However, it should be considered that within a certain time span, different pathologies could alter their patterns of temperature. A deeper understanding of the different time courses of injuries is important to clarify the benefit of MIT in injury management and to define whether a thermogram is “normal” or not. In terms of quantification of side-to side differences within a defined ROI, it is important to use the medical analysis function of image fusion. The main advantage of MIT is its safety, however, the disadvantage of MIT results from its physical limitations. The non-radiating, two-dimensional technique provides information about surface structures. A conclusion of processes in deeper tissues needs to be further investigated by combining different medical imaging modalities. In addition, it must be clearly stated that the aim of MIT use in sports medicine is not to be a substitute for clinical examination, but to enhance and support it. It can be concluded that MIT is a reliable, low-cost detection tool that should be applied for pre-scanning athletes.

 

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An International Perspective on Topics in Sports Medicine and Sports Injury, ISBN: 978-953-51-0005-8

 

An Overview of Recent Application of Medical Infrared Thermography in Sports Medicine in Austria

Carolin Hildebrandt,1,* Christian Raschner,1 and Kurt Ammer2

Abstract

Medical infrared thermography (MIT) is used for analyzing physiological functions related to skin temperature. Technological advances have made MIT a reliable medical measurement tool. This paper provides an overview of MIT’s technical requirements and usefulness in sports medicine, with a special focus on overuse and traumatic knee injuries. Case studies are used to illustrate the clinical applicability and limitations of MIT. It is concluded that MIT is a non-invasive, non-radiating, low cost detection tool which should be applied for pre-scanning athletes in sports medicine.

 

1. Introduction

Medical infrared thermography (MIT) provides a non-invasive and non-radiating analysis tool for analyzing physiological functions related to the control of skin-temperature. This rapidly developing technology is used to detect and locate thermal abnormalities characterized by an increase or decrease found at the skin surface. The technique involves the detection of infrared radiation that can be directly correlated with the temperature distribution of a defined body region [1].

An injury is often related with variations in blood flow and these in turn can affect the skin temperature. Inflammation leads to hyperthermia, whereas degeneration, reduced muscular activity and poor perfusion may cause a hypothermic pattern [2]. There are several applications of MIT in the field of human medicine, such as neurological disorders [3], open- heart surgery [4], vascular diseases [5], reflex sympathetic dystrophy syndrome [6], urology problems [7] and mass fever screening [8]. Much research has been focused on the successful evaluation of breast cancer [9]. According to Ng [10] breast thermography has achieved an average sensitivity and specificity of 90%. He reported that an abnormal breast thermogram is a significant biological marker for breast cancer. One possible explanation is that increased blood flow due to the vascular proliferation that results from angiogenesis is associated with tumors [11]. Reduced skin temperature has also been implicated in musculoskeletal disorder (MSD). In fact, a cold skin pattern around ankle sprains indicates a poor prognosis and a long recovery time [12].

Infrared sensor technology also contributes to the field of injury management in athletic animals [13–16]. Anatomical and physiological similarities between animals and humans may imply that modern infrared sensor technology can provide significant information for the functional management of injuries in human athletes. However, there is scant scientific evidence of its successful application in the field of human sports medicine.

High performance training pushes the locomotor system to the edge of its anatomical and physiological limits. The knee is a weak link and is the most frequently affected joint in sports. Knee injuries are common in skiing and sports that involve jumping and abrupt direction changes [17]. Current trends indicate that in Austria, one of the top ski countries, the number of participants in competitive alpine skiing is greatly increasing, triggering a proliferation of knee injuries [18]. The incidence of long-term effects, such as osteoarthritis, are alarming.

These injuries usually involve a long, costly rehabilitation period and are often career-ending for athletes. The need for further research in the field of injury prevention and management is crucial to counteract severe skiing injuries.

 

2. International Status of Medical Infrared Imaging

MIT has been recognized by the American Medical Association council as a feasible diagnostic tool since 1987 and was recently acknowledged by the American Academy of Medical Infrared Imaging. Various groups and associations promote the proper application of thermal imaging in the practice of sports medicine. These groups include the European Association of Thermology, the United Kingdom Thermography Association, and the Northern Norwegian Centre for Medical Thermography, the American Academy of Thermology and the German Society of Thermography and Regulation Medicine (DGTR) as one of the oldest medical thermography society. The overall aim of these groups is to further improve reliable standardized methods and to develop appropriate protocols for clinical application.

The usefulness of MIT in sports medicine has been noted often [19]. However, some doubts about the technology highlight the necessity of doing further research. The major argument is whether MIT can accurately determine thermal variations to enable sufficient quantitative analyses [20]. Proponents of MIT state that “state-of-the-art” computerized systems using complex statistical data analysis ensure high quality results [21] and that thermal sensitivity has increased, creating a new dimension that should be exploited and applied [22].

The absence of a standardized reference images is also a problem [23]. A research group from the University of Glamorgan is currently conducting research to determine “normal” thermograms by creating an “Infrared Atlas of Normal Human Skin Temperature Distribution”. Well-designed research studies can address these issues and help to resolve them.

 

3. Principles and Technique of Infrared Thermography

 

3.1. Electromagnetic Spectrum

There are several medical imaging modalities within the electromagnetic spectrum, which is defined as the range of electromagnetic radiation frequencies. Depending on their physical principles, these various techniques mainly provide anatomical information.

MIT is essentially a digital two-dimensional imaging technique that provides data about the physiology of tissues [24]. Unlike most diagnostic modalities, MIT is non-invasive. The question is whether physiological images can change prior to anatomic disruption. Specific software makes it possible to incorporate anatomical and physiological information by image fusion, which helps to localize the affected area and extent of the injury.

All images are obtained through the energy from the human tissue, leading to a classification based on the energy applied to the body. The energy content of the emission is related to the wavelength of the radiation.

Regarding the spectral region, human skin is a black body radiator with an emissivity factor of 0.98 [25] and is therefore a perfect emitter of infrared radiation at room temperature. Planck’s law describes the characteristics of infrared radiation emitted by an object in terms of spectral radiant emittance [26].

W(λ,T)=2πhc2λ4¯¯¯¯¯¯¯¯[exp(hcλkT)−1]−1Wcm−2μm−1

Formula 1. Planck’s radiation law.

  • H (Planck’s constant) = 6.6256 × 10−34 Js
  • K (Boltzmann’s constant) = 1.38054 × 10−23 WsK−1
  • C (velocity of light in vacuum) = 2.9979 × 108 ms−1
  • μ = wavelength in μm
  • T = temperature in K

Human skin emits infrared radiation mainly in the wavelength range of 2–20 μm with an average peak of 9–10 μm [25]. Based on Plank’s Law roughly 90% of the emitted infrared radiation in humans is of longer wavelength (8–15 μm).

 

4. Infrared Radiation

Emissivity refers to an object’s ability to emit radiation [27]. Infrared cameras generate images based on the amount of heat dissipated at the surface by infrared radiation. The technology is a sophisticated way of receiving electromagnetic radiation and converting it into electrical signals. These signals are finally displayed in gray shades or colors which represents temperature values. Human heat energy is transferred to the environment via four mechanisms [28]:

  1. Conduction: the transfer of heat energy via tissue layer by contact between two bodies of different temperatures;
  2. Convection: the heat change between the skin and the surroundings; and
  3. Radiation: a transfer of heat that does not require a medium. The energy is transferred between two separate objects at different temperatures via electromagnetic waves (photons)
  4. Sweat Evaporation: which is the main mechanism for heat dissipation during exercise? The conversion of liquid into vapor allows the body to regulate its temperature. Evaporation results in a decrease of surface temperature.

The constructed thermogram yields a quantitative and qualitative temperature map of the surface temperature, which can be related to distinct pathological condition and blood flow.

Different to a single detector thermal camera, focal plane array detectors generate thermal images of high resolution without a mechanical scan mechanism. These cameras operate in the long wave infrared region (8–15 μm) with the advantage that they are less affected by sunlight compared to the shorter waves.

 

4.1. The 21st Century Technique

The medical usefulness of infrared thermography has been proven over the last several years but has largely been done without the advantage of 21st century techniques [29].

A new generation of high-resolution cameras has been developed, leading to improved diagnostic capability. Changes in the thermal pattern that may be very small but still meaningful can be properly assessed.

These technical enhancements have made infrared thermography into a reliable and powerful measurement tool [30]. It has opened opportunities for very precise measurements by imaging very subtle changes in skin surface temperature.


4.2. Recommended Requirements for Human Medicine

The thermal imaging group from the University of Glamorgan has recently published a battery of tests for checking the reliability of an infrared camera [23,31].

An infrared camera suitable for evaluating human skin profiles should have the following [31–33]:

  1. High Spatial resolution which reflects the separation between two nearby spots. A resolution of 320 (horizontal) × 240 (vertical) pixel is the minimum requirement. The spatial resolution is very dependent on image focusing.
  2. High Thermal resolution as an expression of sensitivity, defined as the minimum temperature difference that can be measured at two distinct spots.
  3. Medical CE certification is recommended: As soon as a temperature value in degree celcius is stated, the device is classified as a medical modality with a measuring function and should be signed by a specific CE approval.
  4. Narrow Calibration range accustomed to the human temperature range (i.e., 20–40 °C) assures more detailed temperature readings.
  5. Medical examination software including an export function, for medical analysis report and well-designed software tools for data analysis and image fusion

 

5. Reliability Study

Reliable measurements have a substantial impact on the diagnosis and interpretation of pathophysiological abnormalities. Many investigations about reliability have focused on equipment and errors related to the physical principles of the technique [31,37]. In addition to technical variations, biological changes such as the circadian rhythm may also contribute noise to the measurements [38].

The reproducibility of the thermal pattern is important if MIT is to be used as a screening tool for injuries. Selfe et al. [36] conducted a study of inter-rater reliability and determined that MIT generated adequately reliable thermal patterns from the anterior knee.

The amount of heat emitted from the knee is a complex phenomenon that is influenced by many factors and comparing images over time requires good standardization methods and quality assurance [39]. We conducted a preliminary study to evaluate the day-to-day repeatability [40].

 

5.1. Methods of Reliability Study

Mean temperature readings of the anterior aspect of the knee of 15 subjects were analyzed. To eliminate inter-rater error, the same person carried out the measurements each time. The examination was conducted according to the “Glamorgan Protocol” which was established to ensure quality control when using MIT for medical applications [23].

To provide consistency for repeated measurements, anatomical landmarks were marked on the subject to delineate the region of interest for data capture.

 

5.2. Results

While high individual variations in knee temperature between subjects were noted, low variations between day-to-day measurements indicated the overall stable temperature of the knee. The one-way random intra-class correlation coefficient (ICC) indicated good intra-examiner reliability for absolute values of mean temperature for the right leg and moderately good reproducibility for the left leg In agreement with other studies, we concluded that MIT is a promising evaluation tool when administered under standardized conditions [1,39–41]. The results of these studies were recently published in the journal Thermology International and provide a more detailed description of methods [40].

 

6. Clinical Application in Alpine Skiing

Previous research has demonstrated that thermal images from the two sides of the body are usually symmetrical [42,43]. Any significant asymmetry of more than 0.7 °C can be defined as abnormal and may indicate a physiologic or anatomical variant in the loco-motor system. By comparing one side with the other, it may be possible to detect sub clinical problems before they are clinically relevant.

One of the most beneficial contributions of MIT to sports medicine may be in the field of preventive medicine. Turner et al. [14] examined tendonitis in racehorses and thermographically detected hot spots two weeks before clinical evidence of swelling, pain and lameness. Early detection of abnormal changes in the tissues is important to counteract overuse injuries. The knee is exposed to a lot of physical stress during the alpine skiing competition season. The so-called “little traumatologies” are very frequent; therefore, their early detection is important [44]. However, it must be emphasized that the primary goal is to detect irregularities in the symmetry of temperature distribution rather than the measurement and comparison of absolute temperatures.

There are currently no quick screening tools that are sufficiently predictive of impending symptoms. To verify the thesis that MIT could predict symptoms, we conducted a pre-season measurement of 35 female and 52 male junior alpine ski racers. This study included likewise athletes who were in rehabilitation after traumatic and acute injuries.

 

6.1. Methods

Following an acclimatization period of 20 minutes, we recorded an image of the anterior/posterior and medial/lateral aspect of both knees with an infrared camera (TVS500EX). A fixed distance of 95 cm from the camera to the subject was used.

Data were stored and analyzed with the iREPORT 2007 software, provided by the GORATEC GmbH. All images were corrected using an emissivity factor of 0.98. Image fusion was used to identify the area of interest. The room temperature remained constant ranging from 21.5–22.3 °C. Equally the relative humidity showed stable values over time (35–38%).

Infrared images were taken twice to get pre- and postseason measurements. Thermographic evaluation was done according to the guidelines prepared by the medical members of the American Academy of Thermology (AAT) and the Glamorgan protocol [23], which incorporates the following seven aspects:

  • Patient communication
  • Patient preparation
  • Patient assessment
  • Examination guidelines
  • Review of the imaging examination
  • Presentation of the findings
  • Exam time recommendation continuing professional education

An experienced team of sports physiotherapists conducted the musculoskeletal examination to obtain data about the functional aspects of the knees. Each subject had to fill in a questionnaire to get additional information about:

  • Name, age, sex
  • Sport history including information about training performed in the previous 7 days
  • Health status
  • Nutritional status
  • Menstrual cycle

 

6.2. Case Studies

 

6.2.1. Overuse Injuries

A common problem in alpine skiing is the occurrence of overuse injuries such as patellae tendinopathy, which is characterized by swelling, pain and tenderness above the tibial tuberosity [45]. This regional problem becomes apparent in the form of a hyperthermic pattern, in which the right knee is affected. The preseason training program includes excessive jumps, leading to mechanical strain and overuse of the patella tendon.

In this study, a total of seven athletes showed symptoms of regional overuse reactions. The symptomatic athletes had a mean side temperature differences of 1.4 °C (±0.58 °C). The normal temperature range of the eight non-injured athletes showed a side-to-side variation of 0.3 °C (±0.61 °C).

Four of the injured athletes reported pain, while the others were asymptomatic at that time. However, physical examination of the knee revealed that this hyperthermia was associated with a low threshold for pressure pain, as previously described in the literature [46].

Early detection and subsequent early therapy intervention program can reduce the severity of symptoms. Furthermore, the detection of at-risk athletes makes it possible to adjust their training program.

 

6.2.2. Traumatic Injuries

Epidemiological studies have shown a high incidence of serious knee injuries among alpine skiers, with the most common injury being the rupture of the anterior cruciate ligament (ACL) [47,48]. A clear decline in swelling and inflammation can be seen. However, pain sensation is still present on the medial aspect of the right knee, as indicated by the hyperthermic area.

Severe alpine skiing accidents may result in serious injuries such as fractures. In Figure 6, the infrared image on the right side was taken 3 months after a combined fracture of the tibia and fibula with intramedulary nailing. This injury resulted in a clear demarcation and localization making it possible to define the extent of the high metabolic activity in structures involved.

Following treatment, no clear differences of the temperature distribution between the two sides could be noted. In conjunction with the clinical examination, the complete recovery was confirmed. However, a high temperature on the shank can be noted on both legs, possibility due to increased muscular activity. Follow up imaging is required for long-term evaluation.The incidence of soft tissue injuries such as muscle strains is relatively small in alpine skiing [44]. However, these injuries are a strong risk factor for future strain injury to the same muscle. Full recovery needs to be assured and may be visualized threw thermal imaging.

It is very important to understand the pathophysiology, phases and time frame of normal tissue healing of traumatic injuries. Regular MIT measurements within the rehabilitation process provide information about the ongoing healing process and improve the therapist’s ability to create an adapted rehabilitation and treatment program. Infrared images may give full recovery information by indicating by low side-to-side differences and decreasing the likelihood of re-injury by returning to the sport too quickly.

These results are based on primary investigations and can be regarded as a first step to provide a scientific database for validating overuse and acute knee injuries when examined with MIT. Further research is intended to distinguish between normal and abnormal temperature patterns [49].

 

7. Limitations and Advantages of Infrared Imaging

The efficiency, safety and low cost of MIT make it an auxiliary tool in medical imaging and diagnostics [19,50]. It can be applied without any objections because this non-invasive technique works without damaging radiation. It has the potential for performing in vivo diagnosis on tissues without the need of sample excision; hence, it can be regarded as a passive measurement [30]. Furthermore, the resulting real time information can be used as instant feedback for the patient or athlete. Innovative concepts such as dynamic thermal imaging will be applied to further explore skin thermal properties in response to stresses such as excessive jumping performance and training, as one important part of specific training in alpine skiing [51].

Cutaneous temperature changes during exercise can now be detected by functional thermal imaging using state-of -the art infrared sensor arrays and may provide additional useful data [52–55].

However, infrared thermography becomes even more useful when its limitations are known. For future consideration, it is important to know that this can provide physiological information but cannot define aetiologies and local anatomy. The Individual variability combined with the complex character of thermoregulation limits the interpretation. The lack of specificity makes it necessary to combine these measurements with other, more structural modalities (X-ray, computed tomography), rather than using it as a replacement.

The biggest challenge is to combine the anatomical and physiological information given by the thermal pattern of the skin surface. The use of instrumented techniques to measure circulatory conditions must be considered.

Automated overlay of infrared and visual medical images as well as automated target recognition are also being actively studied [56,57]. By applying these new techniques we may reduce operator dependence and enhance accuracy and objectivity.

 

8. Conclusions

Thermal imaging in medicine is not new, but early investigation with old and insufficient techniques has led to work with dubious results. Recent work with modern 21st century technology has demonstrated the value of MIT in medical application when used as an auxiliary tool. Knowledge about thermoregulation, anatomy, physiology, morphology and pathophysiological processes is important to counteract inaccurate diagnoses.

The aim of this technique is not to be a substitute for clinical examination but to enhance it. Further research and follow-up studies are warranted to create databases for clinical measurements and further determine its viability in real-world medical settings. Empirical evidence of correlation between pathology and infrared imaging is essential to further predict the value of MIR. It should be used as a multidisciplinary assessment tool by experts from different fields.

Based on the advantages of MIT as a non-invasive, non-radiating, low cost first-line detection modality, it should be applied in the field of sports medicine as a pre-scan team assessment tool. The extension of sport specific databases may further contribute to the detection of high risk athletes and help them to start early intervention.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292141/

 

Assessment of hand osteoarthritis: correlation between thermographic and radiographic methods.

Varju G, Pieper CF, Renner JB, Kraus VB.
Box 3416, Duke University Medical Center, Durham, NC 27710, USA.

 

OBJECTIVE:

Anatomical stages of digital osteoarthritis (OA) have been characterized radiographically as progressing through sequential phases from normal to osteophyte formation, progressive loss of joint space, joint erosion and joint remodelling. Our study was designed to evaluate a physiological parameter, joint surface temperature, measured with computerized digital infrared thermal imaging, and its association with sequential stages of radiographic OA (rOA).

 

METHODS:

Thermograms, radiographs and digital photographs were taken of both hands of 91 subjects with nodal hand OA. Temperature measurements were made on digits 2-5 at distal interphalangeal (DIP) joints, proximal interphalangeal (PIP) joints and metacarpophalangeal (MCP) joints (2184 joints in total). We fitted a repeated measures ANCOVA model to analyse the effects of rOA on temperature, with handedness, joint group, digit and NSAID use as covariates.

 

RESULTS:

The reliability of the thermoscanning procedure was high (generalizability coefficient 0.899 for two scans performed 3 h apart). The mean joint temperature decreased with increasing rOA severity, defined by the Kellgren-Lawrence (KL) scale. The mean temperature of KL0 joints was significantly different from that of each of the other KL grades (P <= 0.002). After adjustment for the other covariates, there was a strong association of rOA with joint surface temperature (P<0.001). The earliest discernible radiographic disease (KL1) was associated with a higher surface temperature than KL0 joints (P = 0.01) and a higher surface temperature than any other KL grade. Joint erosions were not associated with a change in joint temperature. CONCLUSION: Joint surface temperature varied with the severity of rOA. Joints were warmer than normal at the onset of OA. As the severity of rOA worsened, joint surface temperature declined. These data support the supposition that digital OA progresses in phases initiated by an inflammatory process. The cooler surface temperatures in later stages of the disease may in part explain the paucity of symptoms reported by patients with hand OA.

http://www.ncbi.nlm.nih.gov/pubmed/15126670


Thermal imaging – a hotspot for the future?: A case report

Ronald J Cook, Shobhan Thakore and Neil M Nichol
Accident and Emergency Department, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK

 

CASE REPORT:

A 6-year-old boy presented to accident and emergency with his mother complaining of a painful right elbow following a fall that day. He fell whilst walking up steps and gave a history of directly striking the elbow on the step. He had not been using the arm since. There was a recent history of a comminuted intra-articular fracture of the proximal ulna of the same elbow, and a cast had been removed just 5 weeks previously.

The patient was seen and examined by an experienced A&E senior house officer. He was difficult to assess and was complaining of pain in the entire arm. There was no swelling or deformity and no apparent bony tenderness to the limb. He was unwilling to actively move the elbow joint, however there was a good range of passive movement throughout the arm and good grip strength was noted. An X-ray of the elbow was performed and no bony injury or effusion of the elbow joint was apparent. The child was treated for a soft tissue injury of the elbow, advised regular analgesia and discharged.

The patient represented two days later complaining of persistent pain to the arm. He was now localising pain to the wrist and there was a corresponding area of tenderness over the distal radius. A thermal image was taken of the limb using a hand held FTI Mv thermal imager interfacing with LIPS Mini PC software. The image identified an obvious “hotspot” corresponding to the area of tenderness over the distal radius, which clearly differed from a thermal image of the normal wrist. Subsequent X-ray of the wrist revealed an undisplaced greenstick fracture of the distal radius. The child was treated with a plaster cast, referred to the orthopaedic fracture clinic and made an uneventful recovery.

 

DISCUSSION:

Thermal Imaging has been considered for use in a wide range of medical circumstances. It has been shown to be useful in aiding diagnosis and guiding management of foot injuries in military recruits when combined with clinical examination, radiographs and bone scanning.4 Telethermography has been demonstrated as a useful tool in aiding diagnosis and management of sports injuries.5 Cole et al. demonstrated a significant relationship between early thermographic assessment of the depth of skin burns and clinical outcome.3 Various types of thermal imaging have also been used in studies of diabetic neuropathic feet,1 the detection of carpal tunnel syndrome,7 the investigation of tendon injuries in horses6 and in the monitoring of undesirable thermal proximity damage during surgical energized dissection and coagulation.2 During the international severe acute respiratory syndrome (SARS) crisis of 2003, thermal imaging was employed as a screening tool at border points. At Singapore’s Changi International airport alone 442,973 passengers were screened and of those 136 identified for further investigation and observation.8 The modality’s sensitivity for identifying passengers with even low grade pyrexia (>37.5 °C) highlights recent technological advances and brings to attention future possible uses.

The main problems previously identified with the use of thermal imaging in the evaluation of a possibly injured limb include a lack of specificity in identifying the site and nature of pathology and difficulty in establishing normal references. While thermography could never replace radiography as a diagnostic tool, it may be useful as an adjunct to clinical examination and X-ray. As this case demonstrates, children can prove difficult to assess in the accident and emergency department environment. Injury localisation in this patient group can prove difficult and the “survey” of a limb with X-ray may result. The use of thermal imaging could improve the sensitivity of clinical examination and therefore assist in injury localisation, preventing unnecessary X-ray exposure.

In this case it may be postulated that thermal imaging has detected a localised increase in temperature associated with the normal inflammatory response to a fracture. This is an early response and if it was shown to be reliable then the modality may be useful in a wider area of emergency medicine. Early radiological findings can be unreliable in conditions such as scaphoid fracture and the “toddler’s” type fracture of the tibial shaft. Thermal imaging could potentially be used in early follow-up to exclude fracture in these situations and prevent prolonged immobilisation and possibly more invasive and expensive bone scanning. It is likely that thermal imaging would be of use when examining bones that are relatively superficial where temperature changes are going to be more apparent.

Thermal imaging has been shown to be effective in assessing the depth of skin burns3 by measuring different skin temperatures created by varying states of perfusion. It may therefore be useful as a real time assessment tool examining changes in peripheral perfusion during the resuscitation of a shocked patient, giving a continuous recording of response to treatment. Modern thermal imaging is rapid, non-invasive, non-emitting and with improving technology becoming more user-friendly and more cost effective. Given these attributes and the potential applications to emergency medicine outlined above, there is a need for our speciality to study the technique further.

 

REFERENCES:

1 D.G. Armstrong, L.A. Lavery and P.J. Liswood et al., Infrared dermal thermometry for the high-risk diabetic foot, Phys Ther 77 (1997) (2), pp. 169–175.
2 P.A. Campbell, A.B. Cresswell and T.G. Frank et al., Real-time thermography during energized vessel sealing and dissection, Surg Endosc 17 (2003) (10), pp. 1640–1645. View Record in Scopus | Cited By in Scopus (25)
3 R.P. Cole, S.G. Jones and P.G. Shakespeare, Themographic assessment of hand burns, Burns 16 (1990) (1), pp. 60–63. Abstract | Article | PDF (512 K) | View Record in Scopus | Cited By in Scopus (30)
4 M. DiBenedetto, M. Yoshida and M. Sharp et al., Foot evaluation by infrared imaging, Military Med 167 (2002), pp. 384–392. View Record in Scopus | Cited By in Scopus (4)
5 U. Garagiola and E. Giani, Use of telethermography in the management of sports injuries, Sports Med 4 (1990), pp. 267–272. View Record in Scopus | Cited By in Scopus (2)
6 C.M. Marr, Microwave thermography: a non-invasive technique for investigation of injury of the superficial digital flexor tendon in the horse, Equine Vet J 24 (1992) (4), pp. 269–273. View Record in Scopus | Cited By in Scopus (9)
7 S. Meyers, D. Cros and B. Sherry et al., Liquid crystal thermography: quantitative studies of abnormalities in carpal tunnel syndrome, Neurology 39 (1989) (11), pp. 1465–1469. View Record in Scopus | Cited By in Scopus (7)
8 A. Wilder-Smith, K.T. Goh and N.I. Paton, Experience of severe acute respiratory syndrome in Singapore: importation of cases, and defense strategies at the airport, J Travel Med 10 (2003), pp. 259– 262. View Record in Scopus | Cited By in Scopus (13) Corresponding author. Tel.: +44 1382 320 464; fax: +44 1382 425 744.

http://www.sciencedirect.com/science/article/pii/S1572346105000413


Thermal signature analysis as a novel method for evaluating inflammatory arthritis activity.

Brenner M, Braun C, Oster M, Gulko PS.
North Shore-LIJ Research Institute, United States.

 

OBJECTIVES:

To determine the potential usefulness of a novel thermal imaging technology to evaluate and monitor inflammatory arthritis activity in small joints using rat models, and to determine whether thermal changes can be used to detect pre-clinical stages of synovitis.

 

METHODS:

Three different rat strains were studied in a monoarticular model of inflammatory arthritis of the ankle induced with an intraarticular (IA) injection of complete Freund’s adjuvant (CFA), and compared with the contra-lateral ankle injected with normal saline. Arthritis activity and severity scores, ankle diameters, pain related posture scores, and thermal images were obtained at ten different time-points between 0h (before induction) and day 7. The pristane-induced arthritis (PIA) model was used to study pre-clinical synovitis. Thermal images were obtained at each time-point using the TSA ImagIR System and digitally analyzed.

 

RESULTS:

Rats developed similar ankle arthritis detected 6h after the IA injection of CFA, which persisted for seven days. All ankle clinical parameters, including arthritis activity and severity scores, significantly correlated with ankle thermal imaging changes in the monoarthritis model (P<0.003). No thermal imaging changes were detected in pre-clinical stages of PIA. However, PIA onset coincided with increased ankle thermal signature.

 

CONCLUSION:

Thermal measurements significantly correlated with arthritis activity and severity parameters. This technology was highly sensitive and could directly measure two cardinal signs of inflammation (warmth and edema – based on ankle diameter) in an area (ankle) that is less than half the size of a human interphalangeal joint, suggesting a potential use to monitor drug responses of rheumatoid arthritis in drug trials or clinical practice.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1798043/


Thermatomal changes in cervical disc herniations.

Yonsei Med J 1999 Oct;40(5):401-12
Zhang HY, Kim YS, Cho YE; Department of Neurosurgery, Yongdong Severance Hospital,
Yonsei College of Medicine, Seoul, Korea.

Subjective symptoms of a cool or warm sensation in the arm could be shown objectively by using thermography with the detection of thermal change in the case of radiculopathy, including cervical disc herniation (CDH). However, the precise location of each thermal change at CDH has not been established in humans. This study used digital infrared thermal imaging (DITI) for 50 controls and 115 CDH patients, analyzed the data statistically with t-test, and defined the areas of thermatomal change in CDH C3/4, C4/5, C5/6, C6/7 and C7/T1. The temperature of the upper trunk and upper extremities of the control group ranged from 29.8 degrees C to 32.8 degrees C. The minimal abnormal thermal difference in the right and left upper extremities ranged from 0.1 degree C to 0.3 degree C in 99% confidence interval. If delta T was more than 0.1 degree C, the anterior middle shoulder sector was considered abnormal (p < 0.01). If delta T was more than 0.3 degree C, the medial upper aspect of the forearm and dorsal aspect of the arm, some areas of the palm and anterior part of the fourth finger, and their opposite side sectors and all dorsal aspects of fingers were considered abnormal (p < 0.01). Other areas except those mentioned above were considered abnormal if delta T was more than 0.2 degree C (p < 0.01). In p < 0.05, thermal change in CDH C3/4 included the posterior upper back and shoulder and the anterior shoulder. Thermal change in CDH C4/5 included the middle and lateral aspect of the triceps muscle, proximal radial region, the posterior medial aspect of the forearm and distal lateral forearm. Thermal change in CDH C5/6 included the anterior aspects of the thenar, thumb and second finger and the anterior aspects of the radial region and posterior aspects of the pararadial region. Thermal change in CDH C6/7 included the posterior aspect of the ulnar and palmar region and the anterior aspects of the ulnar region and some fingers. Thermal change in CDH C7/T1 included the scapula and posterior medial aspect of the arm and the anterior medial aspect of the arm. The areas of thermal change in each CDH included wider sensory dermatome and sympathetic dermatome. There was a statistically significant change of temperature in the areas of thermal change in all CDH patients. In conclusion, the areas of thermal change in CDH can be helpful in diagnosing the level of disc protrusion and in detecting the symptomatic level in multiple CDH patients.

http://www.ncbi.nlm.nih.gov/pubmed/10565248


Foot evaluation by infrared imaging

DiBenedetto, M. , Yoshida, M. , Sharp, M. , Jones, B.
University of Virginia, Dept. of Physical Med. And Rehab., 545 Ray C. Hunt Drive,
Charlottesville, VA 22903-2981, United States

ABSTRACT:

For better assessment of foot injury severity during basic military training, we evaluated a simple noninvasive technique: thermography. With this infrared imaging method, we determined normal foot parameters (from 30 soldiers before training), thermographic findings in different foot stress fractures (from 30 soldiers so diagnosed), and normal responses to abnormal stresses in 30 trainees who underwent the same training as the previous group but did not have musculoskeletal complaints. We found that normal foot thermograms show onion peel-like progressive cooling on the plantar surface, with a medially located warm center at the instep. Thermograms of injured feet show areas of increased heat, but excessive weight-bearing pressures on feet, new shoes, or boots also cause increased infrared emission even without discomfort. Differentiation remains difficult; however, thermography can detect injury early. It does not reveal exact diagnoses, but its greatest benefit is easy follow-up to monitor severity and healing.

http://www.ncbi.nlm.nih.gov/pubmed/12053846


The use of thermal infrared imaging to assess the efficacy of a therapeutic exercise program in individuals with diabetes.

Al-Nakhli HH, Petrofsky JS, Laymon MS, Arai D, Holland K, Berk LS.1 Loma Linda University, Loma Linda, California.

Exercise is of great value for individuals with diabetes in helping to control their hemoglobin A1c levels and in increasing their insulin sensitivity. Delayed-onset muscle soreness (DOMS) is a common problem in healthy individuals and in people who have diabetes. … Conclusion:  Infrared thermal imaging may be a valuable technique of seeing which muscles are sore hours or even days after the exercise is over. Thus, thermal imaging would be an efficient and painless way of looking at DOMS in both healthy individuals and individuals who have diabetes, even if they are facing neurological problems.

http://www.ncbi.nlm.nih.gov/pubmed/22011006


An overview of temperature monitoring devices for early detection of diabetic foot disorders.

Roback K.
Center for Medical Technology Assessment (CMT), Department of Medical and Health Sciences, Linköping University, Linkoping, Sweden.

Diabetic foot complications are associated with substantial costs and loss of quality of life. This article gives an overview of available and emerging devices for the monitoring of foot temperature as a means of early detection of foot disorders in diabetes. The aim is to describe the technologies and to summarize experiences from experimental use. Studies show that regular monitoring of foot temperature may limit the incidence of disabling conditions such as foot ulcers and lower-limb amputations. Infrared thermometry and liquid crystal thermography were identified as the leading technologies in use today. Both technologies are feasible for temperature monitoring of the feet and could be used as a complement to current practices for foot examinations in diabetes.

http://www.ncbi.nlm.nih.gov/pubmed/20822392

The application of infrared thermography in the assessment of patients with coccygodynia before and after manual therapy combined with diathermy.

Wu CL, Yu KL, Chuang HY, Huang MH, Chen TW, Chen CH. Source Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.

ABSTRACT

 

OBJECTIVE:

This study examines the potential usefulness of a novel thermal imaging technique in the assessment of local physiologic responses before and after conservative therapies for coccygodynia.

 

METHODS:

Patients with coccygodynia were selected on the basis of detailed history taking, clinical examination, and dynamic series radiography. They underwent therapeutic modalities consisting of 6 to 8 sessions of manual medicine treatments (massage of the levators followed by Maigne’s manipulative technique) and external physiotherapy (short-wave diathermy) 3 times a week for 8 weeks. We performed the assessments with numeric pain rating scale (NPRS) and infrared thermography (IRT) before treatment and at 12 weeks.

 

RESULTS:

A total of 53 patients (6 males and 47 females) ranging from 18 to 71 years of age and clinically diagnosed with coccygodynia received the full course of therapy and assessments. There were significant differences in both NPRS and surface temperature obtained by IRT in the 12-week follow-up (P < .05). The correlation between NPRS improvement and temperature decrement was significantly high (r = 0.67, P < .01).

 

CONCLUSIONS:

The study shows that IRT can objectively show the decrement of surface temperatures correlating with changes in subjective pain intensity after treatment of coccygodynia. With the advantages of being painless, noninvasive, and easy to repeat, IRT appears to be useful as a quantifiable tool for monitoring the dynamics of the disease activity in coccygodynia.

http://www.ncbi.nlm.nih.gov/pubmed/19447265