A Review of Breast Thermography
William C. Amalu, DC, DIACT (B), FIACT
Note: The following is not a comprehensive review of the literature.
Over 30 years of research compiling over 800 studies in the
index-medicus exist. What follows is a pertinent sample review of the
research concerning the clinical application of diagnostic infrared
imaging (thermography) for use in breast cancer screening. All the
citations are taken from the index-medicus peer-reviewed research
literature or medical textbooks. The authors are either PhD's with
their doctorate in a representative field, or physicians primarily in
the specialties of oncology, radiology, gynecology, and internal
medicine.
The following list is a summary of the informational text that follows:
In 1982, the FDA approved breast thermography as an adjunctive diagnostic breast cancer screening procedure.
Introduction
The first recorded use of thermobiological diagnostics can be found in
the writings of Hippocrates around 480 B.C.[1]. A mud slurry spread
over the patient was observed for areas that would dry first and was
thought to indicate underlying organ pathology. Since this time,
continued research and clinical observations proved that certain
temperatures related to the human body were indeed indicative of normal
and abnormal physiologic processes. In the 1950's, military research
into infrared monitoring systems for night time troop movements ushered
in a new era in thermal diagnostics. The first use of diagnostic
thermography came in 1957 when R. Lawson discovered that the skin
temperature over a cancer in the breast was higher than that of normal
tissue[2].
The Department of Health Education and Welfare
released a position paper in 1972 in which the director, Thomas
Tiernery, wrote, "The medical consultants indicate that thermography,
in its present state of development, is beyond the experimental state
as a diagnostic procedure in the following 4 areas: 1) Pathology of the
female breast. 2)......". On January 29, 1982, the Food and Drug
Administration published its approval and classification of
thermography as an adjunctive diagnostic screening procedure for the
detection of breast cancer. Since the late 1970's, numerous medical
centers and independent clinics have used thermography for a variety of
diagnostic purposes.
Fundamentals of Infrared Imaging
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. Since the emissivity of human skin is extremely high
(within 1% of that of a black body), measurements of infrared radiation
emitted by the 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[3]. 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 artifacts. 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 18-22 degree C, and
kept to within 1 degree C of change during the examination, is
necessary to produce a physiologically neutral image free from
artifact.
Correlation Between Pathology and Infrared Imaging
The empirical evidence that underlying breast cancer alters regional
skin surface temperatures was investigated early on. In 1963, Lawson
and Chughtai, two McGill University surgeons, published an elegant
intra-operative study demonstrating that the increase in regional skin
surface temperature associated with breast cancer was related to venous
convection[4]. This early quantitative experiment added credence to
previous research suggesting that infrared findings were related to
both increased vascular flow and increased metabolism.
Infrared imaging of the breast may have critical
prognostic significance since it may correlate with a variety of
pathologic prognostic features such as tumor size, tumor grade, lymph
node status and markers of tumor growth[5]. The pathologic basis for
these infrared findings, however, is uncertain. One possibility is
increased blood flow due to vascular proliferation (assessed by
quantifying the microvascular density (MVD)) as a result of tumor
associated angiogenesis. Although in one study[6], the MVD did not
correlate with abnormal infrared findings. However, the imaging method
used in that study consisted of contact plate technology (liquid
crystal thermography (LCT)), which is not capable of modern
computerized infrared analysis. Consequently, LCT does not possess the
discrimination and digital processing necessary to begin to correlate
histological and discrete vascular changes[7].
In 1993, Head and Elliott reported that improved
images from second generation infrared systems allowed more objective
and quantitative analysis[5], and indicated that growth-rate related
prognostic indicators were strongly associated with the infrared image
interpretation.
In a 1994 detailed review of the potential of
infrared imaging[8], Anbar suggested, using an elegant biochemical and
immunological cascade, that the previous empirical observation that
small tumors were capable of producing notable infrared changes could
be due to enhanced perfusion over a substantial area of the breast
surface via regional tumor induced nitric oxide vasodilatation. Nitric
oxide is a molecule with potent vasodilating properties. It is
synthesized by nitric oxide synthase (NOS), found both as a
constitutive form of nitric oxide synthase (c-NOS), especially in
endothelial cells, and as an inducible form of nitric oxide synthase
(i-NOS), especially in macrophages[9]. NOS has been demonstrated in
breast carcinoma[10] using tissue immunohistochemistry, and is
associated with a high tumor grade. There have been, however, no
previous studies correlating tissue NOS levels with infrared imaging.
Given the correlation between infrared imaging and tumor grade, as well
as NOS levels and tumor grade, it is possible that infrared findings
may correlate with tumor NOS content. Future studies are planned to
investigate these possible associations.
The concept of angiogenesis, as an integral part of
early breast cancer, was emphasized in 1996 by Guido and Schnitt. Their
observations suggested that it is an early event in the development of
breast cancer and may occur before tumor cells acquire the ability to
invade the surrounding stroma and even before there is morphologic
evidence of an in-situ carcinoma[11]. Anti-angiogenesis therapy is now
one of the most promising therapeutic strategies and has been found to
be pivotal in the new paradigm for consideration of breast cancer
development and treatment[12]. In 1996, in his highly reviewed textbook
entitled Atlas of Mammography - New Early Signs in Breast Cancer,
Gamagami studied angiogenesis by infrared imaging and reported that
hypervascularity and hyperthermia could be shown in 86% of non-palpable
breast cancers. He also noted that in 15% of these cases infrared
imaging helped to detect cancers that were not visible on
mammography[13].
The underlying principle by which thermography
(infrared imaging) detects pre-cancerous growths and cancerous tumors
surrounds the well documented recruitment of existing vascularity and
neoangiogenesis which is necessary to maintain the increased metabolism
of cellular growth and multiplication. The biomedical engineering
evidence of thermography's value, both in model in-vitro and clinically
in-vivo studies of various tissue growths, normal and neoplastic, has
been established[14-20].
The Role of Infrared Imaging in the Detection of Cancer
In order to evaluate the value of thermography, two viewpoints must be
considered: first, the sensitivity of thermograms taken preoperatively
in patients with known breast carcinoma, and second, the incidence of
normal and abnormal thermograms in asymptomatic populations
(specificity) and the presence or absence of carcinoma in each of these
groups.
In 1965, Gershon-Cohen, a radiologist and researcher
from the Albert Einstein Medical Center, introduced infrared imaging to
the United States[21]. Using a Barnes thermograph, he reported on 4,000
cases with a sensitivity of 94% and a false-positive rate of 6%. This
data was included in a review of the then current status of infrared
imaging published in 1968 in CA - A Cancer Journal for Physicians[22].
In prospective studies, Hoffman first reported on
thermography in a gynecologic practice. He detected 23 carcinomas in
1,924 patients (a detection rate of 12.5 per 1,000), with an 8.4%
false-negative (91.6% sensitivity) and a 7.4% false-positive (92.6%
specificity) rate[23].
Stark and Way screened 4,621 asymptomatic women, 35%
of whom were under 35 years of age, and detected 24 cancers (detection
rate of 7.6 per 1,000), with a sensitivity and specificity of 98.3% and
93.5% respectively[24].
In a mobile unit examination of rural Wisconsin,
Hobbins screened 37,506 women using thermography. He reported the
detection of 5.7 cancers per 1,000 women screened with a 12%
false-negative and 14% false-positive rate. His findings also
corroborated with others that thermography is the sole early initial
signal in 10% of breast cancers[25-26].
Reporting his Radiology division's experience with
10,000 thermographic studies done concomitantly with mammography over a
3 year period, Isard reiterated a number of important concepts
including the remarkable thermal and vascular stability of the infrared
image from year to year in the otherwise healthy patient and the
importance of recognizing any significant change[27]. In his
experience, combining these modalities increased the sensitivity rate
of detection by approximately 10%; thus, underlining the
complementarity of these procedures since each one did not always
suspect the same lesion. It was Isard's conclusion that, had there been
a preliminary selection of his group of 4,393 asymptomatic patients by
infrared imaging, mammographic examination would have been restricted
to the 1,028 patients with abnormal infrared imaging, or 23% of this
cohort. This would have resulted in a cancer detection rate of 24.1 per
1000 combined infrared and mammographic examinations as contrasted to
the expected 7 per 1000 by mammographic screening alone. He concluded
that since infrared imaging is an innocuous examination, it could be
utilized to focus attention upon asymptomatic women who should be
examined more intensely. Isard emphasized that, like mammography and
other breast imaging techniques, infrared imaging does not diagnose
cancer, but merely indicates the presence of an abnormality.
Spitalier and associates screened 61,000 women using
thermography over a 10 year period. The false-negative and positive
rate was found to be 11% (89% sensitivity and specificity). 91% of the
nonpalpable cancers (T0 rating) were detected by thermography. Of all
the patients with cancer, thermography alone was the first alarm in 60%
of the cases. The authors also noted that "in patients having no
clinical or radiographic suspicion of malignancy, a persistently
abnormal breast thermogram represents the highest known risk factor for
the future development of breast cancer"[28].
Two small-scale studies by Moskowitz (150
patients)[29] and Treatt (515 patients)[30] reported on the sensitivity
and reliability of infrared imaging. Both used unknown "experts" to
review the images of breast cancer patients. While Moskowitz excluded
unreadable images, data from Threatt's study indicated that less than
30% of the images produced were considered good, the rest being
substandard. Both of these studies produced poor results; however, this
could be expected from the fact alone that both used such a small
patient base. However, the greatest error in these studies is found in
the methods used to analyze the images. The type of image analysis
consisted of the sole use of abnormal vascular pattern recognition. At
the time these studies were performed, the most recognized method of
infrared image analysis used a combination of abnormal vascular
patterns with a quantitative analysis of temperature variations across
the breasts. Consequently, the data obtained from these studies is
highly questionable. Their findings were also inconsistent with
numerous previous large-scale multi-center trials. The authors
suggested that for infrared imaging to be truly effective as a
screening tool, there needed to be a more objective means of
interpretation and proposed that this would be facilitated by
computerized evaluation. This statement is interesting considering that
the use of recognized quantitative and qualitative reading protocols
(including computer analysis) was available at the time.
In a unique study comprising 39,802 women screened
over a 3 year period, Haberman and associates used thermography and
physical examination to determine if mammography was recommended. They
reported an 85% sensitivity and 70% specificity for thermography.
Haberman cautioned that the findings of thermographic specificity could
not be extrapolated from this study as it was well documented that long
term observation (8-10 years or more) is necessary to determine a true
false-positive rate. The authors noted that 30% of the cancers found
would not have been detected if it were not for thermography[31].
Gros and Gautherie reported on 85,000 patients
screened with a resultant 90% sensitivity and 88% specificity. In order
to investigate a method of increasing the sensitivity of the test,
10,834 patients were examined with the addition of a cold-challenge
(two types: fan and ice water) in order to elicit an autonomic
response. This form of dynamic thermography decreased the
false-positive rate to 3.5% (96.5% sensitivity)[32-35].
In a large scale multi-center review of nearly 70,000
women screened, Jones reported a false-negative and false-positive rate
of 13% ( 87% sensitivity) and 15% (85% sensitivity) respectively for
thermography[36].
In a study performed in 1986, Usuki reported on the
relation of thermographic findings in breast cancer diagnosis. He noted
an 88% sensitivity for thermography in the detection of breast
cancers[37].
In a study comparing clinical examination,
mammography, and thermography in the diagnosis of breast cancer, three
groups of patients were used: 4,716 patients with confirmed carcinoma,
3,305 patients with histologically diagnosed benign breast disease, and
8,757 general patients (16,778 total participants). This paper also
compared clinical examination and mammography to other well known
studies in the literature including the NCI-sponsored Breast Cancer
Detection Demonstration Projects. In this study, clinical examination
had an average sensitivity of 75% in detecting all tumors and 50% in
cancers less than 2 cm in size. This rate is exceptionally good when
compared to many other studies at between 35-66% sensitivity.
Mammography was found to have an average 80% sensitivity and 73%
specificity. Thermography had an average sensitivity of 88% (85% in
tumors less than 1 cm in size) and a specificity of 85%. An abnormal
thermogram was found to have a 94% predictive value. From the findings
in this study, the authors suggested that "none of the techniques
available for screening for breast carcinoma and evaluating patients
with breast related symptoms is sufficiently accurate to be used alone.
For the best results, a multimodal approach should be used"[38].
In a series of 4,000 confirmed breast cancers,
Thomassin and associates observed 130 sub-clinical carcinomas ranging
in diameter of 3-5 mm. Both mammography and thermography were used
alone and in combination. Of the 130 cancers, 10% were detected by
mammography only, 50% by thermography alone, and 40% by both
techniques. Thus, there was a thermal alarm in 90% of the patients and
the only sign in 50% of the cases[39].
In a study by Gautherie and associates, the
effectiveness of thermography in terms of survival benefit was
discussed. The authors analyzed the survival rates of 106 patients in
whom the diagnosis of breast cancer was established as a result of the
follow-up of thermographic abnormalities found on the initial
examination when the breasts were apparently healthy (negative physical
and mammographic findings). The control group consisted of 372 breast
cancer patients. The patients in both groups were subjected to
identical treatment and followed for 5 years. A 61% increase in
survival was noted in the patients who were followed-up due to initial
thermographic abnormalities. The authors summarized the study by
stating that "the findings clearly establish that the early
identification of women at high risk of breast cancer based on the
objective thermal assessment of breast health results in a dramatic
survival benefit"[40-41].
In a simple review of over 15 studies from 1967-1998,
breast thermography has showed an average sensitivity and specificity
of 90%. With continued technological advances in infrared imaging in
the past decade, some studies are showing even higher sensitivity and
specificity values. However, until further large scale studies are
performed, these findings remain in question.
Breast Cancer Detection and Demonstration Projects
The Breast Cancer Detection and Demonstration Project (BCDDP) is the
most frequently quoted reason for the decreased use of infrared
imaging. The BCDDP was a large-scale study performed from 1973 through
1979 which collected data from many centers around the United States.
Three methods of breast cancer detection were studied: physical
examination, mammography, and infrared imaging (breast thermography).
Inflated Expectations -
Just before the onset of the BCDDP, two important papers appeared in
the literature. In 1972, Gerald D. Dodd of the University of Texas
Department of Diagnostic Radiology presented an update on infrared
imaging in breast cancer diagnosis at the 7th National Cancer
Conference sponsored by the National Cancer Society and the National
Cancer Institute[42]. In his presentation, he suggested that infrared
imaging would be best employed as a screening agent for mammography. He
proposed that in any general survey of the female population age 40 and
over, 15 to 20% of these subjects would have positive infrared imaging
and would require mammograms. Of these, approximately 5% would be
recommended for biopsy. He concluded that infrared imaging would serve
to eliminate 80 to 85% of the potential mammograms. Dodd also
reiterated that the procedure was not competitive with mammography and,
reporting the Texas Medical School's experience with infrared imaging,
noted that it was capable of detecting approximately 85% of all breast
cancers. Dodd's ideas would later help to fuel the premise and
attitudes incorporated into the BCDDP. Three years later, J.D. Wallace
presented to another Cancer Conference, sponsored by the American
College of Radiology, the American Cancer Society and the Cancer
Control Program of the National Cancer Institute, an update on infrared
imaging of the breast[43]. The author's analysis suggested that the
incidence of breast cancer detection per 1000 patients screened could
increase from 2.72 when using mammography to 19 when using infrared
imaging. He then underlined that infrared imaging poses no radiation
burden on the patient, requires no physical contact and, being an
innocuous technique, could concentrate the sought population by a
significant factor selecting those patients that required further
investigation. He concluded that, "the resulting infrared image
contains only a small amount of information as compared to the
mammogram, so that the reading of the infrared image is a substantially
simpler task".
Faulty Premise -
Unfortunately, this rather simplistic and cavalier attitude toward the
generation and interpretation of infrared imaging was prevalent when it
was hastily added and then prematurely dismissed from the BCDDP which
was just getting underway. Exaggerated expectations led to the
ill-founded premise that infrared imaging might replace mammography
rather than complement it. A detailed review of the Report of the
Working Group of the BCDDP, published in 1979, is essential to
understand the subsequent evolution of infrared imaging[44]. The work
scope of this project was issued by the NCI on the 26th of March 1973
with six objectives, the second being to determine if a negative
infrared image was sufficient to preclude the use of clinical
examination and mammography in the detection of breast cancer. The
Working Group, reporting on results of the first four years of this
project, gave a short history regarding infrared imaging in breast
cancer detection. They wrote that as of the sixties, there was intense
interest in determining the suitability of infrared imaging for
large-scale applications, and mass screening was one possibility. The
need for technological improvement was recognized and the authors
stated that efforts had been made to refine the technique. One of the
important objectives behind these efforts had been to achieve a
sufficiently high sensitivity and specificity for infrared imaging
under screening conditions to make it useful as a pre-screening device
in selecting patients for referral for mammographic examination. It was
thought that if successful, this technology would result in a
relatively small proportion of women having mammography (a technique
that had caused concern at that time because of the carcinogenic
effects of radiation). The Working Group indicated that the sensitivity
and specificity of infrared imaging readings, with clinical data
emanating from inter-institutional studies, were close to the
corresponding results for physical examination and mammography. They
noted that these three modalities selected different sub-groups of
breast cancers, and for this reason further evaluation of infrared
imaging as a screening device in a controlled clinical trial was
recommended.
Poor Study Design - While
this report describes in detail the importance of quality control of
mammography, the entire protocol for infrared imaging was summarized in
one paragraph and simply indicated that infrared imaging was conducted
by a BCDDP trained technician. The detailed extensive results from this
report, consisting of over 50 tables, included only one that referred
to infrared imaging showing that it had detected only 41% of the breast
cancers during the first screening while the residual were either
normal or unknown. There is no breakdown as far as these two latter
groups were concerned. Since 28% of the first screening and 32% of the
second screening were picked up by mammography alone, infrared imaging
was dropped from any further evaluation and consideration. The report
stated that it was impossible to determine whether abnormal infrared
imaging could be predictive of interval cancers (cancers developing
between screenings) since they did not collect this data. By the same
token, the Working Group was unable to conclude, with their limited
experience, whether the findings were related to the then available
technology of infrared imaging or with its application. They did,
however, conclude that the decision to dismiss infrared imaging should
not be taken as a determination of the future of this technique, rather
that the procedure continued to be of interest because it does not
entail the risk of radiation exposure. In the Working Group's final
recommendation, they state that "infrared imaging does not appear to be
suitable as a substitute for mammography for routine screening in the
BCDDP." The report admitted that several individual programs of the
BCDDP had results that were more favorable than what was reported for
the BCDDP as a whole. They encouraged investment in the development and
testing of infrared imaging under carefully controlled study conditions
and suggested that high priority be given to these studies. They noted
that a few suitable sites appeared to be available within the BCDDP
participants and proposed that developmental studies should be
solicited from sites with sufficient experience.
Untrained Personnel and Protocol Violations
- JoAnn Haberman, who was a participant in this project[45], provided
further insight into the relatively simplistic regard assigned to
infrared imaging during this program. The author reiterated that
expertise in mammography was an absolute requirement for the awarding
of a contract to establish a Screening Center. However, the situation
was just the opposite with regard to infrared imaging - no experience
was required at all. When the 27 demonstration project centers opened
their doors, only 5 had any pre-existing expertise in infrared imaging.
Of the remaining screening centers, there was no experience at all in
this technology. Finally, more than 18 months after the project had
begun, the NCI established centers where radiologists and their
technicians could obtain sufficient training in infrared imaging.
Unfortunately, only 11 of the demonstration project directors
considered this training of sufficient importance to send their
technologists to learn proper infrared technique. The imaging sites
also disregarded environmental controls. Many of the project sites were
mobile imaging vans which had poor heating and cooling capabilities and
often kept their doors open in the front and rear to permit an easy
flow of patients. This, combined with a lack of pre-imaging patient
acclimation, lead to unreadable images.
In summary, with regard to thermography, the BCDDP
was plagued with problems and seriously flawed in four critical areas:
1) Completely untrained technicians were used to perform the scans, 2)
The study used radiologists who had no experience or knowledge in
reading infrared images, 3) Proper laboratory environmental controls
were completely ignored. In fact, many of the research sites were
mobile trailers with extreme variations in internal temperatures, 4) No
standardized reading protocol had yet been established for infrared
imaging. The BCDDP was also initiated with an incorrect premise that
thermography might replace mammography. From a purely scientific point,
an anatomical imaging procedure (mammography) cannot be replaced by a
physiological one. Last of all, and of considerable concern, was the
reading of the images. It wasn't until the early 1980's that
established and standardized reading protocols were introduced.
Considering these facts, the BCDDP could not have properly evaluated
infrared imaging. With the advent of known laboratory environmental
controls, established reading protocols, and state-of-the-art infrared
technology, a poorly performed 20-year-old study cannot be used to
determine the appropriateness of thermography.
Thermography as a Risk Indicator
As early as 1976, at the Third International Symposium on Detection and
Prevention of Cancer in New York, thermography was established by
consensus as the highest risk marker for the possibility of the
presence of an undetected breast cancer. It had also been shown to
predict such a subsequent occurrence[46-48]. The Wisconsin Breast
Cancer Detection Foundation presented a summary of its findings in this
area, which has remained undisputed[49]. This, combined with other
reports, has confirmed that thermography is the highest risk indicator
for the future development of breast cancer and is 10 times as
significant as a first order family history of the disease[50].
In a study of 10,000 women screened, Gautherie found
that, when applied to asymptomatic women, thermography was very useful
in assessing the risk of cancer by dividing patients into low- and
high-risk categories. This was based on an objective evaluation of each
patient's thermograms using an improved reading protocol that
incorporated 20 thermopathological factors[51].
From a patient base of 58,000 women screened with
thermography, Gros and associates followed 1,527 patients with
initially healthy breasts and abnormal thermograms for 12 years. Of
this group, 40% developed malignancies within 5 years. The study
concluded that "an abnormal thermogram is the single most important
marker of high risk for the future development of breast cancer"[35].
Spitalier and associates followed 1,416 patients with
isolated abnormal breast thermograms. It was found that a persistently
abnormal thermogram, as an isolated phenomenon, is associated with an
actuarial breast cancer risk of 26% at 5 years. Within this study, 165
patients with non-palpable cancers were observed. In 53% of these
patients, thermography was the only test which was positive at the time
of initial evaluation. It was concluded that: 1) A persistently
abnormal thermogram, even in the absence of any other sign of
malignancy, is associated with a high risk of developing cancer, 2)
This isolated abnormal also carries with it a high risk of developing
interval cancer, and as such the patient should be examined more
frequently than the customary 12 months, 3) Most patients diagnosed as
having minimal breast cancer have abnormal thermograms as the first
warning sign[52-53].
Current Status of Detection
Current first-line breast cancer detection strategy still depends
essentially on clinical examination and mammography. The limitations of
the former, with its reported sensitivity rate often below 65%[54] is
well-recognized, and even the proposed value of self-breast examination
is now being contested[55]. While mammography is accepted as the most
reliable and cost-effective imaging modality, its contribution
continues to be challenged with persistent false-negative rates ranging
up to 30% [56-57]; with decreasing sensitivity in patients on estrogen
replacement therapy[58]. In addition, there is recent data suggesting
that denser and less informative mammography images are precisely those
associated with an increased cancer risk[59]. Echoing some of the
shortcomings of the BCDDP concerning their study design and infrared
imaging, Moskowitz indicated that mammography is also not a procedure
to be performed by the untutored[60].
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 tumor growth.
While promising, techniques such as scintimammography[61], doppler
ultrasound[62], and MRI[63], 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. While
practical, this step-wise approach currently results in the
non-recognition, and thus delayed utilization of second-line technology
in approximately 10% of established breast cancers[60]. This is
consistent with study published by Keyserlingk et al[64].
Because of thermography's unique ability to image the
thermovascular aspects of the breast, extremely early warning signals
(from 8-10 years before any other detection method) have been observed
in long-term studies. Consequently, thermography is the earliest known
indicator for the future development of breast cancer. It is for this
reason that an abnormal infrared image is the single most important
marker of high risk for developing breast cancer. Thus, thermography
has a significant place as one of the major front-line methods of
breast cancer detection.
Conclusion
The large patient populations and long survey periods in many of the
above 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 (a contribution
that has been established and justified by the unequivocal relationship
between heat production and tumor 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 early detection of breast cancer.
Ongoing research into the thermal characteristics of breast pathologies
will continue to investigate the relationships between neoangiogenesis,
chemical mediators, and the neoplastic process.
It is unfortunate, but many physicians still hesitate
to consider thermography as a useful tool in clinical practice in spite
of the considerable research database, continued improvements in both
thermographic technology and image analysis, and continued efforts on
the part of the thermographic societies. This attitude may be due to
the fact that the physical and biological bases of thermography are not
familiar to most physicians. The other methods of cancer investigations
refer directly to topics of medical teaching. For instance, radiography
and ultrasonography refer to anatomy. Thermography, however, is based
on thermodynamics and thermokinetics, which are unfamiliar to most
physicians, though man is experiencing heat production and exchange in
every situation he undergoes or creates.
Considering the contribution that thermography has demonstrated thus
far in the field of early cancer detection, all possibilities should be
considered for promoting further technical, biological, and clinical
research in this procedure.
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