Minimal-invasive thermal imaging of a malignant tumor: a simple model and algorithm.

Minimal-invasive thermal imaging of a malignant tumor: a simple model and algorithm.

Gescheit IM, Dayan A, Ben-David M, Gannot I.

Source

Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel.

Abstract

PURPOSE:

This article deals with the development of a minimal-invasive, infrared (IR) (8-12 microm spectral range) imaging technique that would improve upon current methods by using superparamagnetic nanostructured core/shell particles for imaging as well as for therapy. This technique may function as a diagnostic tool, thanks to the ability of specific bioconjugation of these nanoparticles to a tumor's outer surface. Hence, by applying an alternating magnetic field, the authors could cause a selective elevation of temperature of the nanoparticles for +1 - +5 degrees C, enabling tumor's imaging. Further elevation of the temperature over +10 degrees C will cause a necrotic effect, leading to localized irreversible damage to the cancerous site without harming the surrounding tissues. This technique may also serve as a targeted therapeutic tool under thermal feedback control.

METHODS:

Under alternative magnetic field, these biocompatible nanoparticles can generate heat, which propagates along the tissue (by thermal conduction), reaching the tissue's surface. Surface temperature distribution can be acquired by an IR camera and analyzed to retrieve nanoparticles' temperature and location within the tissue. An analytical-based steady-state solution for the thermal inverse problem was developed, considering an embedded point heat source. Based on this solution, the authors developed an algorithm that generates solutions for the corresponding forward problem, and based on discovered relations between the problem's characteristic, can derive the depth and temperature of the embedded heat source from the surface temperature profile, derived from the thermal image.

RESULTS:

The algorithm was able to compute the heat source depth and power (proportional to its temperature) in two phases. Assuming that the surface temperature profile can be fitted to a Lorentzian curve, the first phase computing the source depth was based on a linear relation between the depth and the FWHM value of the surface temperature profile, which is independent of the source power. This relation varies between different tissues and surface conditions. The second phase computing the power (Q) was based on an exponential relation between the area (A) curve of the surface temperature profile and power (Q), dependent on the depth computed in the first phase. The simulation results show that given the tissue thermal properties, the surface conductance, and the ambient conditions, an inverse solution can be applied retrieving the depth and temperature of a point heat source from a 2D thermal image.

CONCLUSIONS:

The predicted depth and heat source power were compared to the actual parameters (which were derived). Differences between the real and estimated values may occur primarily in computing the forward solution, which was used for the estimation itself. The fact that the computation is carried out discretely and the spatial resolution in the radial direction are influencing factors. To improve and eliminate these factors, the resolution may be increased or suitable interpolation and/or smoothing may be applied. Applying this algorithm on a spherical heat source volume may be feasible. A solution for the forward problem was established, yet incorporation of the source radius has to be further examined.

Thermoregulation and thermography in neonatal physiology and disease.

Thermoregulation and thermography in neonatal physiology and disease.

Knobel RB, Guenther BD, Rice HE.

Source

School of Nursing, Duke University, Durham, NC, USA, Jean & Georgia Brumley, Jr. Neonatal-Perinatal Research Institute, Duke University School of Medicine, Durham, NC, USA. robin.knobel@duke.edu

Abstract

INTRODUCTION:

Infrared thermal imaging, or thermography, is a technique used to measure body surface temperature in the study of thermoregulation. Researchers are beginning to use this novel methodology to study cancer, peripheral vascular disease, and wound management.

METHODS:

The authors tested the feasibility of using an FLIR SC640 uncooled, infrared camera to measure body temperature in neonates housed in heated, humid incubators. The authors examined thermograms to analyze distributions between central and peripheral body temperature in extremely low birth weight infants. The authors have also used this technology to examine the relationship between body temperature and development of necrotizing enterocolitis in premature infants.

RESULTS:

Handheld, uncooled, infrared cameras are easy to use and produce high-quality thermograms that can be visualized in grayscale or color palettes to enhance qualitative and quantitative analyses.

CONCLUSION:

Future research will benefit from the use of this noninvasive, inexpensive measurement tool. Nurse researchers can use this methodology in adult and infant populations to study temperature differentials present in pathological conditions

The Use of Thermography in the Diagnosis of CRPS: A Physician's Opinion

The Use of Thermography in the Diagnosis of CRPS: A Physician's Opinion

BY PHILIP GETSON, DO

This article appeared in The Pain Practitioner, The Journal of the American Academy of Pain Management, vol. 16, no 1, 2006

EXPERTS WHO EVALUATE PATIENTS WITH CRPS [Complex Regional Pain Syndrome] make the diagnosis based upon history and physical examination. However, because of the wide variation in symptom complexes, not every individual presents with the "classic" symptoms that are
frequently associated with CRPS (e.g., temperature change, color change, and hair growth change).

In the past, attempts have been made to diagnosis CRPS with triple phase bone scans. Some literature
suggests that these are about 40% accurate, but I believe that in reality the number is closer to 15%. This test is frequently non-specific in its representation, and rarely do radiologists offer a diagnosis of CRPS when they have not been provided with that historical information. Electrodiagnostic testing (EMGs), CAT Scans, MRIs, etc., have no appreciable value in assisting in the diagnosis of CRPS.

Thermography has been utilized in medical application since the 1950s. Prior to that it had, and still does have, industrial applications. The use of infrared imaging for neuromuscular purposes dates back to the 1960's and has continued despite lack of widespread acceptance. Numerous articles have been written regarding the value of thermography in the diagnosis of sympathetically mediated pain syndromes and work in this area continues. The July 2002 United States Department of Health and Human Services document on reflex sympathetic dystrophy, suggests thermography as the diagnostic tool for the evaluation of CRPS.

In the 24 years since I began using neuromuscular thermography in my practice, we have examined thousands of patients with neuromuscular disorders. Using electronic thermographic apparatus, the cameras (which were initially driven by liquid nitrogen) are now hi-tech computer-generated images that allow us to view the nervous system by measuring changes in skin temperature. These changes are controlled by the sympathetic nervous system and alterations in the sympathetics cause alterations in thermal (infrared) imaging which do not conform to dermatomal patterns.

While electrodiagnostic testing may show a radiculopathic pattern, such testing often errs because EMGs measure motor function as opposed to sensory function, which is the fundamental basis for CRPS. The mechanism of thermal imaging allows for perception of altered skin temperature to one-tenth of one degree centigrade. The lack of symmetry which is out of conformation to dermatomal distribution patterns goes a long way to confirming the clinical diagnosis of CRPS.

Measurements taken on an individual within approximately the first six months of the onset of the
pathology will show the affected side to be warmer than the contra lateral side by temperature gradient in excess of 0.9 degrees centigrade (considered by this observer to be the standard for sympathetically mediated thermal asymmetry). Frequently this asymmetry exceeds 1.5 or 2 degrees and is clearly not the result of vascular pathology per se. After approximately six months the pattern changes with the affected side being the "cold side." It is therefore imperative that a history of the traumatic event which precipitated CRPS be afforded the thermographic expert.

As can be seen from the images (included with this article), the temperature differential is often dramatic. While the human hand is capable of perceiving significant temperature differential between two sides, the thermal imaging camera is hundreds of times more sensitive and the temperature scale (unlike the human hand) and can be adjusted to incorporate variations in room and human body temperature, which varies from individual to individual. Additionally, this author is currently collecting data that clearly indicates that the migratory pattern of CRPS can be documented as much as six to nine months prior to the occurrence of symptomatology in a limb that has been affected with sympathetically-mediated dysfunction, but has not yet become symptomatic at the time the images were performed. It is fascinating to see patients who offer verbal complaints (in completed schematic diagram) about one limb, yet manifest thermal abnormalities in an entirely separate area.

In addition to the benefits in diagnosing sympathetically mediated pain syndromes, new thermographic cameras have the potential to offer real-time imaging capabilities that could allow monitoring of an affected limb during the surgical implantation of a spinal cord stimulator. By stimulating the affected nerve (thereby causing a "warming" of the damaged limb), the surgeon could place the leads accurately and "know" they were in the exact place to afford the individual the maximum benefit to be derived from such implantation. This would reduce the randomization factor currently in place by allowing for an electronic "road map" which otherwise does not exist. Similar use of thermal imaging for surgical or chemical ablations of sympathetic nerve dysfunction is possible.

In conclusion, thermographic (infrared) imaging appears to be the best, if not only diagnostic tool, that should be utilized by the clinician for objectification of a clinical diagnosis of sympathetically mediated pain syndromes. The overused adage, "A picture is worth 1000 words" is particularly applicable here, not only to assist the clinician in making the diagnosis, but to add verification to the patients' symptoms, particularly in instances where they have been led to believe they are "crazy" because conventional diagnostic testing does not offer objective evidence of their symptom complex. Research on thermographic imaging is on-going, bur as a diagnostic tool, much of its potential remains untapped. The number of people who have benefited from the conclusive diagnosis of CRPS by thermographic means continues to grow, thereby allowing clinicians an opportunity for earlier intervention of treatment to an affected body part.

PHILIP GETSON, DO, has been certified by the American Academy of Thermology, the American Herschel Society, the Academy of Neuromuscular Thermology and is a Diplomate of the American Medical Infrared Association. He has lectured extensively in the field of Thermography especially as to its usage in the diagnosis of R.S.D. He is currently working on three separate papers on the subject.

Headaches

Ford Headache Clinic, Birmingham, AL 35213, USA.

We reviewed thermograms of 993 suitable patients with migraine with and without aura, chronic daily headache, cluster headache, posttraumatic headache, and a variety of other headache types. Eight hundred fifty-five (86.1%) had abnormal thermograms usually characterized by decreased supraorbital thermal emission. Six hundred ninety-four (69.9%) of 993 had migraine without aura of whom 593 (85.4%) had abnormal thermograms. Two hundred two (20.3%) of 993 had migraine with aura, of whom 180 (89.1%) had abnormal thermograms. Thirty of 35 (85.7%) patients with cluster headache, and 28 of 33 (84.8%) with posttraumatic headache had abnormal thermograms. Twenty-four of 29 (82.8%) of patients with various less common headaches and head pain syndromes had abnormal thermography. Previous studies have indicated that about 67 to 84% of patients with migraine have abnormal thermograms. Some reports have indicated fewer have thermal asymmetries in migraine without aura, and even fewer with "mixed or muscle contraction" headaches. Our study indicates a somewhat greater number of headache patients have abnormal thermograms than has generally been reported. We conclude digital infrared thermography is a useful diagnostic test in the management of headaches.

Clinical Application Of Thermography In Dentistry

Clinical Application Of Thermography In Dentistry

Thermography measurement in the clinical set up can be done on a given spot or over an extended area of interest. Infrared telethermography of the face in normal subjects have shown that men have higher temperatures than females. The rationale behind this is that men have more basal metabolic than women and his skin dissipates more heat per unit area of body surface. Similarly age and ethnicity variations in facial temperature can also occur. [14-16]

In Chronic Orofacial pain patients

Gratt and his colleagues in 1996 developed a classification system using telethermographs for patients with chronic pain. [17] They classified them as normal when selected anatomic area (∆T) values range from 0.0 to +0.250C, hot when it is >0.350C, and cold when it is <0.350C. When a selected anatomic area value is 0.26- 0.350C, the finding is classified as equivocal. Moreover they also found that hot thermographs had the clinical diagnosis of (1) sympathetically maintained pain, (2) peripheral nerve mediated pain, (3) TMJ arthropathy, or (4) maxillary sinusitis. Subjects classified with cold subareas on their thermographs were found to have the clinical diagnosis of (1) peripheral nerve-mediated pain (2) sympathetically independent pain. Subjects classified with normal telethermographs included patients with the clinical diagnosis of (1) cracked tooth syndrome (2) trigeminal neuralgia (3) pretrigeminal neuralgia (4) psychogenic facial pain. This system of thermal classification resulted in 92% agreement in classifying pain patients making it as an important diagnostic parameter. [12,17]

In TMJ disorders

Normal TMJ examination using thermography had showed symmetrical thermal patterns with a mean

∆T values of 0.10C. [12, 14, 18] On the other hand, patients affected with internal derangement and TMJ osteoarthritis showed ∆T values of +0.40C. [19, 20] Beth and Gratt in 1996 conducted a double-blinded clinical study to compare the ∆T values among active orthodontic patients, TMD patients and symptomatic TMJ controls. The results showed that the average TMJ area ∆T values as +0.20C, +0.40C, and +0.10C in these groups respectively.(21) The above findings suggest that tele-thermography can distinguish between patients undergoing active orthodontic treatment and patients with TMD. [12,21]

In quantification of thermal insult to pulp

Dental pulpal tissue is exposed to variety of thermal insult during various dental treatment modalities.

Of late for debonding of orthodontic brackets Eelectro Thermal Ddebonding (ETD) method is widely used, this technique although has many advantages than the conventional mechanical method can pose serious thermal damage to pulp. Cummings and his colleagues in 1999 performed an in-vitro study on extracted human premolar teeth applying ETD. Thermal imaging analysis was done using mercury cadmium terullide detector showed that the pulpal temperature increased from 16.80C- 45.60C, which can pose serious threat to pulpal vitality. It can be stated from the study that, ETD methods needs intermittent cooling of the teeth with simultaneous thermal imaging to prevent pulpal damage. [22] Similarly the use of ultra high speed air-driven instrumentation during cavity preparation can result in serious thermal insult to the pulp. To overcome this, it is believed that various coolants (air water spray or air/water alone) can be used to reduce the intrapulpal temperature and prevent subsequent damage to the pulp. It was only until 1979, when Carson and his colleagues performed a study employing thermography to determine the pattern of heat distribution and dissipation during ultra-speed cavity preparation using both an air-water spray and air only coolants to determine if a point heat source is generated. This study stated that the mean magnitude of temperature increases with both types of coolant, 2.80C and 3.670C, probably does not exceed the physiologic limits of the pulp. [23] 

In assessing inferior alveolar nerve deficit

Over the years numerous studies have shown that thermal imaging technique can play a vital role in effective assessment of inferior alveolar nerve deficit. [12,24] Gratt and his colleagues in 1994 stated that patients with inferior alveolar nerve deficit when examined showed ∆T values of +0.50C on the affected side whereas subjects with no inferior alveolar nerve deficit showed a symmetrical thermal ∆T value of +0.10C. [25] The authors stated that the changes are due to blockage of the vascular neuronal vasoconstriction and this was confirmed by the same colleagues in the same year when similar thermological picture was obtained in normal subjects by temporary blockage of the inferior alveolar nerve using 2% lidocaine. [26]

Qualitative evaluation of N2O concentration

N2O is a highly insoluble gas which is rapidly absorbed and is eliminated swiftly by the lungs, thus it is used widely either alone or in combination with other anesthetic agents. [27] Results of various studies have shown that leakage of N2O into the workplace can lead to adverse health effects such as reproductive, hematologic and nervous dysfunctions. [28] Studies on acute and chronic occupational exposures have shown that N2O air concentration levels as low as 50 parts per million (ppm) can result in bone marrow depression, paresthesias, altered concentration, impaired visual effects, alterations in vitamin B12 and plasma homocysteine concentrations. [29-31]

In response to these findings and in order to effectively control exposures several guidelines have been published that define appropriate use and control criteria for N2O usage. The ADA made 10 recommendations that address the use of appropriate engineering controls for proper scavenging. [32] However, they are proved futile and health hazards secondary to N2O exposure is still on the rise. Rademaker et al in 2009 conducted a study using infrared thermography to determine the effectiveness of two N2O scavenging systems- The Safe Sedate Dental Mask (Airgas, Radnor, Pa.) system (System I) and Porter Nitrous Oxide Sedation System (Porter Instrument, Hatfield, Pa.) (System II). The results suggested that neither of the system was able to control occupational exposure of N2O oxide below the NIOSH REL. [33]

Additional applications of telethermography

- Evaluation of cranio mandibular disorders. [34]

- Detection of carotid occlusal disease. [35]

- Quantification of the effects of post-surgical inflammation. [36]

- Quantification of the effects of analgesics, anti-inflammatory drugs, etc.

- In the diagnosis of myofacial symptoms.

Conclusion

Thermography aids in the assessment and staging of various dysfunctions of the head and neck region.

The unique significance of thermography is both qualitative and quantitative assessment which helps in estimation of progression of the disease in a systematic manner. With the innovation of novel equipments and the state of the art facility, thermography in the near future will certainly re-emerge as a unique research tool in dentistry.

References

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