Mammography (also called mastography ) is the process of using low-energy X-rays (usually around 30 kVp) to examine human breast for diagnosis and screening. The purpose of mammography is early detection of breast cancer, usually through characteristic or microcalsification mass detection.
Like all X-rays, a mammogram uses an ionizing radiation dose to create an image. These images are then analyzed for abnormal findings. It is common to use low-energy X-rays, usually Mo (x-ray K-shell energy of 17.5 and 19.6 keV) and Rh (20.2 and 22.7 keV) than those used for bone radiography. Ultrasound, ductography, positron emission mammography (PEM), and magnetic resonance imaging (MRI) are in addition to mammography. Ultrasound is usually used for further evaluation of the masses found in mammography or the palpable mass not seen in mammograms. Ductograms are still used in some institutions for the evaluation of nipple discharge when the mammogram is not diagnostic. MRI can be useful for further evaluation of questionable findings, as well as for screening of pre-surgical evaluation in patients with known breast cancer, to detect additional lesions that may alter surgical approaches, for example, from lumpectomy of breast involvement to mastectomy. Other procedures under investigation include thomosynthesis.
For the average woman, the US Prevention Services Task Force recommends (2009) mammography every two years between the ages of 50 and 74. American College of Radiology and the American Cancer Society recommend annual mammography beginning at age 40. The Canadian Preventive Health Care Task Force (2012) and the European Cancer Observatory (2011) recommend mammography every 2 to 3 years between the ages of 50 and 69. This task force report shows that in addition to unnecessary surgery and anxiety, the risk of more frequent mammograms includes an increase small but significant in breast cancer caused by radiation. In addition, mammograms should not be performed with increasing frequency in patients undergoing breast surgery, including breast augmentation, mastopection, and breast reduction. The Cochrane Collaboration (2013) concluded after ten years that trials with adequate randomization found no mammography screening effects on total cancer mortality, including breast cancer. The Cochrane review authors wrote: "If we assume that screening reduces breast cancer mortality by 15% and overdiagnosis and over-treatment is 30%, that means that for every 2,000 women invited for a 10-year screening, someone will avoid dying because breast cancer and 10 healthy women, who will not be diagnosed if there is no screening, will be treated unnecessarily. In addition, more than 200 women will experience significant psychological distress including anxiety and uncertainty over the years due to false-positive findings. " concluded that the time had come to reassess whether universal mammography screening should be recommended for all age groups. They state that universal screening may not make sense. The Nordic Cochrane Collection updated the research in 2012 and stated that advances in diagnosis and treatment make mammography screening less effective today, making it "ineffective". They concluded that "it would no longer make sense to attend" for breast cancer screening at any age, and warn of misleading information on the internet.
Mammography has a negative (undetectable) cancer level of at least ten percent. This is partly due to the dense tissue that obscures cancer and the emergence of cancer in mammograms that have a large overlap with the appearance of normal tissue. A meta-analysis review of programs in countries with organized screening found a 52% over-over diagnosis rate.
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The use of mammography as a screening tool for detecting early breast cancer in asymptomatic healthy women is controversial.
Keen and Keen show that recurrent mammography beginning at age fifty saves about 1.8 lives for 15 years for every 1,000 screened women. These results should be seen against the adverse effects of errors in diagnosis, over-treatment, and radiation exposure. Cochrane's analysis of screening showed that "it is not clear whether screening is better than damage". According to their analysis, 1 in 2,000 women will prolong their life by 10 years of screening, while 10 healthy women will undergo unnecessary breast cancer treatment. In addition, 200 women will suffer significant psychological stress due to false positive results. Newman showed that mammography screening did not reduce overall mortality, but caused significant damage by causing cancer fear and unnecessary surgical intervention. The Nordic Cochrane Collection notes that advances in the diagnosis and treatment of breast cancer can make breast cancer screening no longer effective in reducing deaths from breast cancer, and therefore no longer recommend routine checks for healthy women because the risks outweigh the benefits.
Often women are depressed enough to be recalled for diagnostic mammograms. Most of these withdrawals will be false positive results. Of every 1,000 US women screened, about 7% will be recalled for diagnostic sessions (although some studies estimate the number is close to 10% to 15%). About 10 of these people will be referred for biopsy; The remaining 60 cases were found to be benign causes. Of the 10 referred for biopsy, about 3.5 will have cancer and 6.5 are not. Of the 3.5 who suffer from cancer, about 2 will have early stage cancer that will heal after treatment.
Mammography can also produce false negatives. Estimates of the number of cancers lost by mammography are usually about 20%. The reasons for not seeing cancer include observer error, but more often it is because the cancer is hidden by other dense tissues in the breast, and even after a mammogram review, cancer can not be seen. Furthermore, one form of breast cancer, lobular cancer, has a growth pattern that produces shadows on mammograms that can not be distinguished from normal breast tissue.
Mortality
Cochrane Collaboration states that the best quality evidence does not show mortality or decreased mortality from all types of cancer from mammography screening.
The Canadian Task Force found that for women aged 50 to 69, checking 720 women every 2 to 3 years for 11 years would prevent 1 death from breast cancer. For women ages 40 to 49, 2,100 women need to be screened at the same frequency and period to prevent one death from breast cancer.
Women whose breast cancer is detected by mammography screening before the onset of a lump or other symptoms generally assume that mammograms "save their lives". In practice, most of these women do not receive the practical benefits of mammograms. There are four categories of cancers found by mammography:
- Cancer is so easily treated that the next detection will produce the same healing rate (women will live without even mammography).
- Cancer is so aggressive that early detection is too late to benefit the patient (the woman who died despite being detected by mammography).
- Cancer that will recede on its own or grow very slowly so that the woman will die of other causes before the cancer produces symptoms (mammography results in excessive diagnosis and over-treatment of this class).
- A small number of breast cancers detected by mammography screening and whose treatment outcomes have improved as a result of earlier detection.
Only 3% to 13% of breast cancers detected by mammography screening fall into this last category. Clinical trial data show that 1 woman per 1,000 healthy women screened for 10 years fall into this category. Mammography screening does not produce benefits for 87% to 97% of women. The probability that a woman falls into one of the four categories above varies with age.
The 2016 review for the US Enforcement Service Task Force found that mammography was associated with a small decrease in breast cancer mortality, but this decline was not statistically significant at any age. The same study found that mammography lowered the risk of advanced cancer among women aged 50 and older, but not among those aged 39 to 49 years.
False positives
The purpose of each screening procedure is to examine a large patient population and find the smallest number most likely to have serious conditions. These patients are then referred for further testing, usually more invasive. So the screening exam is not meant to be definitive; but is intended to have sufficient sensitivity to detect a useful proportion of cancers. Higher sensitivity costs are more suspicious results in patients without disease. This is true about mammography. Patients without recalled disease for further testing of the examination sessions (about 7%) are sometimes referred to as "false positives". There is a trade-off between the number of patients with the disease found and the much larger number of patients without the disease to be re-screened.
Research shows that false-positive mammograms can affect women's well-being and behavior. Some women who receive false-positive results may be more likely to return for routine examination or breast self-examination more frequently. However, some women who receive false-positive results become anxious, worried, and sad about the possibility of developing breast cancer, a feeling that can last for years.
False positives also mean greater costs, both for individuals and for screening programs. Because advanced screening is usually much more expensive than initial screening, more false positives (to be acted upon) mean fewer women can be screened for a certain amount of money. Thus when the sensitivity increases, screening programs will be more expensive or limited for screening a small number of women.
Overdiagnosis
The major deterioration of mammography breast cancer screening is overdiagnosis: detection of abnormalities that meet the pathological definition of cancer but will never develop to cause symptoms or death. Dr. H. Gilbert Welch, a researcher at Dartmouth College, stated that "detectable breast on screen and prostate cancer patients are more likely to be diagnosed excessively than actually helped by the test." Estimates of overdiagnosis associated with mammography range from 1% to 54%. In 2009, Peter C. Gotzsche and Karsten Juhl JÃÆ'¸rgensen reviewed the literature and found that 1 in 3 cases of detectable breast cancer in the population offered mammography screening was undiagnosed. In contrast, the 2012 panel hosted by the national cancer director for the UK and Cancer Research UK concluded that 1 in 5 breast cancer cases diagnosed among women who had undergone breast cancer screening were too undiagnosed. This means the over-diagnosis rate of 129 women per 10,000 invited for screening.
Negative wrong
Mammograms also have missed tumor levels, or "false negative." Accurate data on the number of false negatives is very difficult to obtain because a mastectomy can not be performed on any woman who has had a mammogram to determine a false negative number. Estimates of false negative numbers depend on the follow-up of a large number of patients over the years. This is difficult in practice because many women do not go back for regular mammography so it is impossible to tell if they have had cancer. In his book The Politics of Cancer , Dr. Samuel S. Epstein claims that in women aged 40 to 49, 1 in 4 cancers are lost in every mammography. Researchers have found that breast tissue is denser among younger women, making it difficult to detect tumors. For this reason, false negatives are twice as likely to occur in pre-menopausal mammograms (Prate). This is why screening programs in the UK do not start calling women for mammogram screening until the age of 50 years.
The importance of this missed cancer is unclear, especially if the woman gets an annual mammogram. Research on closely related situations has shown that small cancers that are not immediately acted upon, but observed for several years, will have good results. A group of 3,184 women have mammograms that are formally classified as "probably benign." This classification is for abnormal patients but has some minor attention. This result is not in the biopsied patient, but in follow-up mammography every 6 months for 3 years to determine whether there is a change of status. Of these 3,184 women, 17 (0.5%) did have cancer. Most importantly, when the diagnosis is finally made, they are all still stage 0 or 1, the earliest stage. Five years after the treatment, none of these 17 women had any evidence of reoccurrence. Thus, early small cancers, although not immediately acting, can still be cured.
Other risks
The radiation exposure associated with mammography is a potential risk of screening, which appears to be greater in younger women. The largest study of radiation risk from mammography concluded that for women aged 40 years and older, the risk of radiation-induced breast cancer is very small, especially compared to the potential benefits of mammography screening, with a 48.5 life-risk ratios ratio stored for each life lost due to radiation exposure. Organizations such as the National Cancer Institute and the United States Preventive Task Force consider these risks when formulating screening guidelines.
The majority of health experts agree that breast cancer risk for asymptomatic women under 35 is not high enough to warrant the risk of radiation exposure. For this reason, and because the sensitivity of breast radiation in women under 35 may be greater than in older women, most radiologists will not screen for mammography in women under 40. However, if there is a significant cancer risk in certain patients (BRCA positive, positive family history, palpable mass), mammography may still be important. Often, radiologists will try to avoid mammography by using ultrasound or MRI imaging.
There is ample evidence to show clearly that there is an excessive cancer diagnosis when women are screened. These cancers will never affect these women in their lives. This over-diagnosis estimate is 10 diagnosed and unnecessary breast cancer per person saved when 2,000 women are screened for 10 years.
While screening between the ages of 40 and 50 is controversial, the evidence suggests that there are some small benefits in terms of early detection. Today, the American Cancer Society, the American College of Radiology, and the American Congress of Obstetricians and Gynecologists encourage an annual mammogram beginning at age 40. The National Cancer Institute encourages a one to two year mammogram for women ages 40 to 49. In contrast, the American College of Physicians, a large group of internal medicines, has recently encouraged individualized screening plans compared to the overall biennial screening for women aged 40 to 49. In 2009, the US Preventive Services Task Force recommended that screening of women age 40 to 49 be based on individual risk factors, and that screening should not be routine in this age group. Their report says that the benefits of screening before the age of 50 do not outweigh the risks.
Pain
The mammography procedure can be painful. The reported pain rate ranges from 6-76%, with 23-95% experiencing pain or discomfort. Experiencing pain is a significant predictor of women not returning to screening.
Maps Mammography
Procedures
During the procedure, the breast is compressed using a special mammography unit. Parallel plate compression flattens the thickness of the breast tissue to improve image quality by reducing the thickness of the tissue that x-rays must penetrate, reducing the amount of radiation dispersed (reducing the image quality), reducing the required radiation dose, and holding the breast still (preventing blurry movement). In mammography screening, a head-to-toe (craniocaudal, CC) display and a mediolateral oblique (MLO) image on the breast were taken. Diagnostic mammography may include these and other views, including enlarged geometric and spot-compressed views of specific areas of concern. Deodorants, powders or lotions may appear on X-rays as a calcium point, so women are not advised to apply them on the day of their exam. There are two types of mammogram research: mammogram screening and diagnostic mammogram. Screening mammograms, consisting of four standard X-ray images, are performed annually in patients who come without symptoms. Diagnostic mammograms are provided for patients with symptoms of breast, changes, or abnormal findings seen in their screening mammograms. Diagnostic mammograms are also performed in patients with breast implants, breast reduction, and patients with a personal and/or family history of breast cancer.
Until a few years ago, mammography was usually done with screen film cassettes. Today, mammography is undergoing a transition to a digital detector, known as digital mammography or Full Field Digital Mammography (FFDM). The first FFDM system was approved by the FDA in the US in 2000. This progress occurs several years later than general radiology. This is caused by several factors:
- Higher spatial resolution demands than mammography
- The cost of equipment increased significantly
- The attention by the FDA that digital mammography equipment shows that it is at least as good as screen film mammography in detecting breast cancer without increasing the dose or number of women called for further evaluation.
As of March 1, 2010, 62% of facilities in the United States and its territory have at least one FFDM unit. (FDA including the radiographic unit is calculated in this figure.)
Mammograms can be seen by one (one reading) or two (double read) trained professionals: the film readers are generally radiologists, but may also be radiographers, radiotherapists, or breast doctors (non-radiologist doctors specializing in breast disease). Double reading, which is standard practice in the UK, but less common in the US, significantly increases the sensitivity and specificity of the procedure. Clinical decision support systems can be used with digital mammography (or digital images of analog mammography), but research suggests that this approach does not improve performance significantly or only slightly improves.
Digital
Digital mammography is a special form of mammography that uses digital receptors and computers instead of x-ray films to help examine breast tissue for breast cancer. Electrical signals can be read on a computer screen, allowing for more image manipulation to allow radiologists to see the results more clearly. Digital mammography may be "spot view", for breast biopsy, or "full field" (FFDM) for screening.
Digital mammography is also used in stereotactic biopsies. Breast biopsy can also be performed using different modalities, such as ultrasound or magnetic resonance imaging (MRI).
While radiologists look forward to more tangible improvements, the effectiveness of digital mammography was found to be comparable to traditional x-ray methods in 2004, although there may be a reduction in radiation by the technique and may result in fewer retesting. In particular, it performs no better than film for post-menopausal women, representing more than three-quarters of women with breast cancer. The US Prevention Task Force concluded that there was not enough evidence to recommend or challenge digital mammography.
Digital mammography is a NASA spin-off, utilizing the technology developed for the Hubble Space Telescope. In 2007, about 8% of American screening centers used digital mammography. Worldwide, the system by Fujifilm Corporation is the most widely used. In the United States, GE digital imaging units typically cost US $ 300,000 to $ 500,000, much more than film-based imaging systems. Costs may decrease as GE begins to compete with the cheaper Fuji system.
3D Mammography
Three-dimensional mammography, also known as digital breast tomosynthesis (DBS), tomosynthesis, and 3D breast imaging, is a mammogram technology that creates 3D breast images using X-rays. When used in addition to ordinary mammography, the results are more positive. Cost effectiveness is unclear by 2016. Another concern is that it is more than double the radiation exposure.
Scoring
Mammogram results are often expressed in the BI-RADS Rating category, often called "BI-RADS scores." Categories range from 0 (incomplete) to 6 (Biopsies known - proven malignancies). In the UK the mammogram is rated on a scale of 1-5 (1 = normal, 2 = benign, 3 = indeterminate, 4 = suspicious malignancy, 5 = malignant). Evidence suggests that accounting for genetic risk factors increases the predicted risk of breast cancer. Process
"Working"
In recent years, the process of "work" has become very formal. It generally consists of screening mammography, diagnostic mammography, and biopsy when necessary, often performed through stereotactic core biopsies or ultrasound guided core biopsies. After mammogram screening, some women may have an area of ​​concern that can not be solved only with information available from screening mammograms. They will then be recalled for a "diagnostic mammogram". This phrase basically means a mammogram for troubleshooting. During this session, the radiologist will monitor any additional films taken by radiographers. Depending on the nature of the findings, ultrasound may often be used as well.
Generally, the cause of unusual appearance is found benign. If the cause can not be determined for benign with sufficient certainty, a biopsy will be recommended. The biopsy procedure will be used to obtain the actual tissue from the site for the pathologist to examine microscopically to determine the exact cause of the disorder. In the past, biopsy was most often performed in surgery, under local or general anesthesia. The majority are now performed with needles in conjunction with ultrasound or mammography guides to ensure that the area of ​​concern is the biopsied area. This core biopsy requires only local anesthesia, similar to what will be given during minor dental procedures.
History
As a medical procedure that induces ionizing radiation, the origin of mammography can be traced to the discovery of X-rays by Wilhelm RÃÆ'¶ntgen in 1895. In the late 1950s Robert Egan at MD Anderson Cancer Center University of Texas incorporated a low kVp technique with high mA and emulsion film single to design a mammography screening method for the first time. He published this result in 1959 in a paper, and later in a 1964 book titled Mammography . "Egan Techniques", as is known, allow doctors to detect calcification in breast tissue; of 245 breast cancers confirmed by biopsy among 1,000 patients, Egan and colleagues at M.D. Anderson was able to identify 238 cases using his method, 19 of whom were in patients whose physical examinations showed no breast abnormalities. The use of mammography as a screening technique spreads clinically after a 1966 study showing the impact of mammograms on death and treatment led by Philip Strax. This new study, based in New York, is the first large-scale randomized controlled trial for mammography screening.
Rule
Mammography facilities in the United States and its territories (including military bases) are subject to the Mammography Quality Standards Act (MQSA). This Act requires annual inspection and accreditation every 3 years through an FDA-approved body. Facilities found to be deficient during inspection or accreditation process may be prohibited from performing mammograms until corrective action has been verified or, in extreme cases, may be required to notify past patients that their examinations are substandard and should not be relied upon.
At the moment, MQSA applies only to traditional mammography and not to related scans, such as breast ultrasound, stereotactic breast biopsy, or breast MRI.
See also
- Computed tomography laser mammography
- Molecular breast imaging
- Xeromammography
References
Further reading
- Reynolds, Handel. The Big Squeeze: A Social and Political History of the Controversial Mammogram (Press ILR Press/Cornell University; 2012) ISBN 978-0-8014-5093-8. 128 pages; The history of controversy about mammography since the 1970s; focus on women's movement and breast cancer activism.
External links
- Homepage Mammography Image Analysis
- Statement of the National Cancer Institute on Mammography Screening
- Screening Mammogram: Questions and Answers, from the National Cancer Institute
- American Cancer Society: Mammogram and Other Breast Enlargement Procedures
- US. Preventive Task Force recommendations on mammography screening
Source of the article : Wikipedia
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