Physics:
All objects with a temperature above absolute zero (-273 K) emit infrared radiation from their surface. The Stefan-Boltzmann Law defines the relation between radiated energy and temperature by stating that the total radiation emitted by an object is directly proportional to the object's area and emissivity and the fourth power of its absolute temperature. The emissivity of human skin is extremely high (within 1% of that of a standard black phantom), therefore, measurements of infrared radiation emitted by the human skin can be converted directly into accurate temperature values.
Equipment Considerations:
Infrared rays are found in the electromagnetic spectrum within the wavelengths of 0.75 micron - 1mm. Human skin emits infrared radiation mainly in the 2 - 20 micron wavelength range, with an average peak at 9-10 microns. State-of-the-art infrared radiation detection systems utilize ultra-sensitive infrared cameras and sophisticated computers to detect, analyze, and produce high-resolution diagnostic images of these infrared emissions. The problems encountered with first generation infrared camera systems such as improper detector sensitivity (low-band), thermal drift, calibration, analog interface, etc. have been solved for almost two decades.
Laboratory Considerations:
Thermographic examinations must be performed in a controlled environment. The primary reason for this is the nature of human physiology. Changes from a different external (non-clinical controlled room) environment, clothing, etc. produce thermal artefacts. Refraining from sun exposure, stimulation or treatment of the breasts, and cosmetics and lotions before the exam, along with 15 minutes of nude acclimation in a florescent lit, draft and sunlight-free, temperature and humidity-controlled room maintained between 18-23 degree C, and kept to within 1 degree C of change during the examination, is necessary to produce a physiologically neutral image free from artefact.
What is Thermography?
Thermography (also called thermal imaging or infrared imaging) was approved by the U.S. Food and Drug Administration (FDA) in 1982 as a supplement to mammography in helping to detect breast cancer. Thermography can help determine whether a local abnormality in breast tissue temperature is present, which may indicate the presence of disease. Though thermography is FDA approved, the exam has not gained acceptance in the medical community as a necessary or effective tool in breast cancer detection. According to the American College of Radiology, thermography has not shown value as a screening, diagnostic, or adjunctive imaging tool.
INFRARED THERMOGRAPHIC BREAST IMAGES
Figure 1: Medial Lt breast DCIS
Figure 2: Left Fibrocystic condition
Figure 3: inflammatory breast disease Rt breast
Figure 4: Normal breast tissue
Is Thermography Useful in Detecting Breast Cancer?
While thermography may be appealing to some women because it is a pain-free exam, most physicians do not recommend thermal imaging. Scientific research over the last 20 years has shown that thermography is not reliable for detecting breast cancer. In 1977, the Beahrs Committee of the National Cancer Institute (NCI) recommended that thermography be discontinued as a routine screening modality in the NCI’s Breast Cancer Detection Demonstration Project.
What is Computerized Thermal Imaging?
Computerized thermal imaging (CTI) is a new, non-invasive imaging method that is being developed using the principles of traditional thermography but with the addition of digital image reconstruction. Computerized thermal imaging (CTI) is a heat sensing and processing system that uses a thermal sensitive camera to capture a digital image based on heat radiating from the body. A computer-assisted interpretation of the digital image helps to determine whether a local abnormality in breast tissue temperature is present, which may indicate the presence of disease. To date, CTI is only available for eligible women who participate in CTI clinical trials; the technology has not yet been approved by the U.S. FDA.
Currently, clinical trials are being conducted across the United States to determine whether the CTI technology may be useful as an adjunct (supplement) to mammography in the breast cancer diagnostic process.
How Does Computerized Thermal Imaging Work?
The main component of the CTI technology is the highly sensitive, high-speed infrared camera. The camera is designed to detect infrared heat given off by the body. After the radiologist has acquired images of the breast tissue, the CTI system uses sophisticated image analysis algorithms and a computer to reconstruct the images to show individual heat patterns. These images differentiate between normal and abnormal heat patterns. The CTI examination consists of the patient being positioned on a special examination bed with the breast suspended in an opening in the top of the bed. The thermal camera is located inside of the bed, focused at the examination area. The physician will use the thermal camera to take a series of images of the breast. The procedure is then repeated with the patient’s other breast. As with traditional thermography, no radiation or breast compression is used during CTI.
After the breast images have been taken, they are analyzed by a computer algorithm and displayed for interpretation by the physician. Breast images are displayed in different colors (red, orange, and yellow) on a computer monitor for the physician to review. Any suspicious area (abnormal heat area) is marked on the digital breast image. The radiologist may then decide whether further breast imaging is necessary. The CTI technology is designed to electronically store the digital breast images and provide the patient with an electronic copy of the images, which may be helpful if she visits another imaging facility.
IMAGES GENERATED BY COMPUTERIZED THERMAL IMAGING:
The left image is the raw thermal image. The right image is a magnified view of the processed image that corresponds to the area of suspicion selected by the green square in the left image. This image shows a very high probability of malignancy (cancer). This patient was rated a BIRAD 4 (suspected malignancy, biopsy recommended) by mammography and confirmed to have ductal carcinoma in situ by biopsy.
What are the Limitations to Computerized Thermal Imaging?
Though computerized thermal imaging (CTI) may provide a pain-free breast imaging exam and has the potential to detect cancer by identifying abnormal heat patterns in breast tissue, there are some limitations to the technology. Since CTI is based on the principles of thermography, it may give false-positive results as thermography often does. A false positive result indicates cancer when no cancer is present. Thermography has a false positive rate of approximately 25%. However, CTI uses more advanced technology and a different exam process than thermal imaging. Thus, clinical trials may find that false positive results are less likely with CTI.
In addition, CTI cannot detect microcalcifications (tiny calcium deposits that may indicate the presence of cancer). Tumours that contain calcifications may be more difficult to remove completely. Microcalcifications can only be seen reliably with mammography. Approximately 50% of the breast cancers detected by mammography appear as a cluster of microcalcifications. Other imaging exams, including thermography, do not provide the fine detail (spatial resolution) that is available with conventional x-ray mammography. However, adjunct exams (such as ultrasound, MRI, etc.,) may be beneficial in some cases because they provide excellent contrast resolution, which may make some abnormalities such as cysts easier to see since these areas "stand out" more from surrounding tissue.
Cost is another limitation of the CTI technology. The manufacturers of CTI technology are only seeking FDA approval for the exam to be used in addition to mammography to help screen for breast cancer. Because mammography will have to be performed regardless of whether or not thermal imaging is done, many physicians question whether CTI technology will drastically change how breast cancer is detected. Many facilities that perform breast imaging tests to screen for breast cancer may be unable or unwilling to acquire additional costly imaging technology if they do not see a significant benefit to the patient.
Current Status of Detection
Currently first-line breast cancer detection strategy still depends essentially on clinical examination and mammography. The limitations of CBE, with its reported sensitivity rate often below 65% is well-recognized, and even the proposed value of self-breast examination is now being contested. Mammography is widely accepted as the most reliable and cost-effective imaging modality, its contribution continues to be challenged, sighting persistent false-negative rates and decreasing sensitivity in patients with high mammographic density. In addition, there is recent data suggesting that denser and less informative mammography images are precisely those associated with an increased cancer risk.
With the current emphasis on earlier detection, there is now renewed interest in the parallel development of complimentary imaging techniques that can also exploit the precocious metabolic, immunological and vascular changes associated with early tumour growth. While promising, techniques such as scintimammography, Doppler ultrasound, and MRI, are associated with a number of disadvantages that include exam duration, limited accessibility, need of intravenous access, patient discomfort, restricted imaging area, difficult interpretation and limited availability of the technology. Like ultrasound, they are more suited to use as second-line options to pursue the already abnormal clinical or mammographic evaluation.
Because of thermography's unique ability to image the thermovascular aspects of the breast, extremely early warning signals have been observed in long-term studies. Consequently, thermography could be used to discover early indicators for the future development of breast cancer. It is for this reason that an abnormal infrared image could be an important marker of high risk for developing breast cancer. Thus, thermography could develop a significant place as one of the major front-line methods of breast cancer detection.
SUMMARY:
The large patient populations and long survey periods in many of the Infrared and CTI clinical studies yields a high significance to the various statistical data obtained. This is especially true for the contribution of thermography to early cancer diagnosis, as an invaluable marker of high-risk populations, and therapeutic decision making. There appears to be an unequivocal relationship between heat production and tumour doubling time.
Currently available high-resolution digital infrared imaging (Thermography) technology benefits greatly from enhanced image production, standardized image interpretation protocols, computerized comparison and storage, and sophisticated image enhancement and analysis. Over 30 years of research and 800 peer-reviewed studies encompassing well over 300,000 women participants has demonstrated thermography's abilities in the detection of breast cancer and distinguishing between low and high risk populations. Ongoing research into the thermal characteristics of breast pathologies will continue to investigate the relationships between neoangiogenesis, chemical mediators, and the neoplastic process.
Considering the contribution that thermography has demonstrated thus far in the field of cancer detection, all possibilities should be considered for promoting further technical, biological, and clinical research in this procedure. I am positive we will hear more about this new modality.
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