Mammography is an essential part of women’s health and since its introduction has made significant advancements in its screening processes. Mammography is a technique using x-rays (low energy photons) to diagnose and locate tumors of the breast. It began with screen film mammography and has advanced into the digital age with both digital and 3D detection. The effects of mammography like the technology has improved since its introduction. These advancements have put a spotlight on its importance. Just as people schedule a yearly teeth cleaning woman over the age of 40 are now including this most important routine exam into their yearly healthcare plan. With mammography screening, the rate of early breast cancer detection has increased significantly and the mortality rate due to breast cancer has declined because of the emphasis on early detection.
Breast cancer is the most common cancer worldwide among women and mammography is known as the premiere standard when it comes to breast cancer screening. The risks for breast cancer can vary depending on the patient and age group. Women who experienced early menstruation, women who experience late onset menopause, women who give birth over the age of 30 years old, long term hormone replacement therapy, the elderly, breast density, a personal history of breast cancer or a family history of breast or ovarian cancer and women who test positive for the BRCA1/BRCA2 gene mutation are all at risk of developing breast cancer. Although breast cancer is predominant in women, men are also susceptible and more likely to be diagnosed with a more advanced stage of breast cancer. The reason for this is that men do not do self-breast exams because they tend to view it as a “women’s issue”.
Women typically begin routine mammogram screenings at the age of 40 years old. Those at higher risk may begin at an earlier age and may potentially have more frequent exams. A physician’s referral is necessary to begin the screening process. Women and men are highly encouraged to perform self-breast exams once a month. There are many signs and/or changes to the breast that are important for people to know. These signs include feeling a thicker than normal area, a dimple or indentation on the breast, hardened residue around the nipple, a red or hot area on the breast, unexpected discharge from the nipple, skin sores on the breast, a bump on the surface of the breast and /or a sunken nipple. Those who experience any of these symptoms should immediately consult their physician
Screen film mammography was the first mode of detection for microcalcifications, tumors and other abnormalities in breast tissue in the United States. It has been the standard technology for over 30 years and has recently been replaced by full field digital mammography within the past 10 years.
Mammography began as screen film mammography. Screen film mammography captures two dimensional images with the use of diagnostic x-rays and film. Mammographers compress different areas of the breast to achieve different views of the tissue. Contrast resolution is an issue for screen film mammography because of the different tissue densities within the breast. The spatial resolution of screen film is particularly high at 16-line pairs per mm. Higher spatial resolution lead to better detection of abnormalities in breast tissue.
Breast density influences the risk associated with breast cancer. Women with a greater concentration of glandular tissue are the most susceptible. The ability of a mammography system to detect abnormalities such as cancer, is termed sensitivity. The greater the sensitivity, the better the system is at detecting things like breast cancer. Screen film sensitivity is comparable to digital but falls short for certain age groups. Breast density affects the diagnosis of breast cancer as well. Denser breast tissue can hide cancers making them harder to detect. Dense breast tissue and malignant cells appear white on film mammograms. This has been a problem for screen film mammography and continues to affect digital mammography today.
Within the past 10 years mammography has made many advancements with the introduction of digital also known as full-field digital mammography often abbreviated as FFDM. Full-field digital mammography is a mammography system in which the x-ray film is replaced by solid-state detectors that convert x-rays into electrical signals. One main advantage of this new technology is the ability to manipulate the contrast resolution on a computer monitor to be able to differentiate between microcalcifications verse just dense or glandular breast tissue. Another advantage of digital mammography is the radiologist’s ability to manipulate the image after acquisition and therefore the need for additional views and repeat exposure to the patient is significantly reduced. Digital mammography offers a much wider dynamic range than screen film mammography. This means the digital detector can differentiate between a wide range of x-ray intensities which provides discrimination between small differences in x-ray attenuation.
The digital images are stored electronically is an incredible advantage of digital mammography because as the images from screen film mammography were stored the image would begin the degrade making it difficult to use them for comparison of newer acquired images. Furthermore, electronic storage of images has many advantages as doctors are able to send images elsewhere for comparison or further interpretation.
Although some may view the higher cost of digital mammography as a disadvantage the benefits of it being more effective in early detection outweigh its expense. Despite digital mammography’s increase in detecting breast cancer, dense breast tissue still poses a challenge.
Full-field digital mammography is still a two-dimensional image, dense breast tissue can hide abnormalities and carcinomas due to superimposition of over-lapping breast tissue. Denser breast tissue has similar attenuative properties as carcinomas making it difficult to differentiate between the two. This can cause is a false-positive result. Many women have been recalled, to obtain further images some even being sent for breast biopsies or to other imaging modalities. This has been shown to cause patients added stress and costs in order to perform these otherwise unnecessary procedures (Cohen, 2013).
Breast density is measured by the amount of fibro glandular tissue present in the breast. Breast tissue is composed of mostly fatty and glandular tissue. Women with dense breasts have a higher amount of glandular and fibrous connective tissue with a low amount of fatty tissue. Regarding mammography breast tissue density is broken up into four categories created by the American College of Radiology (ACR). These categories are as follows: breast made up of mostly fatty tissue found in about 10% of women, breasts containing scattered areas of dense glandular and fibrous connective tissue found in about 40% of women, dense breast tissue made up of many areas of glandular and fibrous connective tissue found in about 40% of women, and extremely dense breast tissue found in about 10% of women (Cancer.gov 2018). It has been suggested that women with denser breast tissue are at an increased risk for developing breast cancer.
In 2011 the Food and Drug Administration approved the use of breast tomosynthesis. Breast tomosynthesis also called three-dimensional (3D) mammography and digital breast tomosynthesis (DBT) is an advanced form of breast imaging similar to CAT scan. Like the other modalities, breast tomosynthesis uses compression of the breast. Compression is used for many reasons, such as maximizing image quality by flattening the layers of breast tissue, decreased patient motion, and decreased radiation dose. However, some have reported that it can be somewhat painful. Like CAT scan the tomosynthesis machine moves across the breast so that once the images are obtained, the computer is able to create a three-dimensional image from captured data.
These images are thin slices allowing the doctors to view tissues and possibly pathologies that may have been previously obscured by overlapping tissues in full-filed digital and screen film mammography. This is a major advantage especially for women with dense breast tissue. The creation of these thin slices has shown that doctors are able to detect the presence of microcalcifications that were otherwise mistaken for dense tissue by simply scrolling through the breast tissue. It has been shown that these microcalcifications can be an early sign of breast cancer.
Digital breast tomosynthesis is often done in addition to digital mammography. In order to reduce patient dose, digital breast tomosynthesis can be used alone and the 2D images can be reconstructed with the same accuracy as conventional digital mammography. While digital mammography typically produces four images digital breast tomosynthesis can create two hundred or more images. The increase in the number of images of Breast tomosynthesis requires longer interpretation time by radiologists it has proven to reduce the recall rate for additional views (Patterson, 2014). This newer advanced technology has shown improvements in visualization and sensitivity.
Patients with dense breast tissue who have digital breast tomosynthesis exams are often sent to ultrasound as part of the routine examination. Ultrasound differentiates between whether an abnormality is an oil filled cyst or a solid mass. If the digital breast tomosynthesis and ultrasound show a clinical indication that the patient should go for further imaging procedures, the next would be MRI or Contrast Enhanced Digital Mammography. This is a common occurrence for women with dense breast tissue who require further clinical evaluation as well as for women with strong family history’s.
Contrast enhanced digital mammography is used to evaluate hypovascularized lesions within the breast. This procedure was first introduced in 1985 (Badr, 2014). Like other angiographic studies contrast is injected into vascular tissue to create a difference in attenuation between the surrounding tissues resulting in a contrast enhanced image.
There are two types of contrast enhanced digital mammography that are being used today. The first is temporal subtraction contrast enhanced mammography and the second is dual-energy contrast enhanced mammography. In temporal subtraction contrast enhanced mammography an image is required of the breast prior to contrast being injected and after contrast has been administered. The two images are then merged to visualize any abnormal changes highlighted by the contrast. Since this method takes two images patient motion is a disadvantage of this procedure. Since the images are taken at different times the tissue can have slightly changed its position making diagnosis more difficult. The two images do present an advantage because the first image captures the breasts morphology and the second captures its vascularity the morphology can be removed from the image effectively.
Dual-energy contrast enhanced mammography avoids the motion disparities common with temporal subtraction mammography because it uses two different x-ray energies at the same time to capture both the vascularity and morphology of the breast tissue simultaneously. The high energy beam interacts primarily with the iodinated contrast to capture the vascularity. While the low energy x-ray beam interacts with the breast tissue free from contrast to capture most of the morphology of the breast.
Both methods are unable to distinguish between benign and malignant tumors, however they can show changes in abnormal structures when compared to previous or future studies. The method of injecting contrast shows any abnormalities in blood flow like that of MRI.
When breast cancer is diagnosed in a patient it is imperative to accurately stage and determine the possible spread of the disease. MRI is the primary tool for staging and evaluation of a cancer diagnosis. It is used to prior to surgery to determine the probable course of action. MRI is not always perfect, in some instance’s tumor size can be mis-measured and the high cost associated with the exam is also a disadvantage. Contrast enhanced digital mammography is an alternative procedure to size tumors and is the less expensive exam. Both MRI and contrast enhanced mammography rely on cancers’ ability to draw in contrast in order to size and stage a tumor effectively. The reason a cancerous tumor is able to draw in the contrast and become visible on the image is due to the fact that they are a new growth of cells and these types of cells tend to be highly vascular, much more vascular compared to normal breast tissue. Therefore, once the contrast is administered if this type of growth is present most of the contrast will travel quickly to the area due to the increased vascularity present in the growth. MRI and contrast enhanced mammography have a similar sensitivity when staging tumors of the same histological type. Making contrast enhanced mammography an affordable alternative as well as being more accessible to patients that cannot undergo an MRI. If a biopsy is required to determine malignancy this cannot be performed with contrast enhanced mammography and must be done under MRI. It would be beneficial if biopsy was possible under dual-energy contrast enhanced mammography because the result would mean patient wouldn’t need to wait for clearance for MRI and the procedure itself, therefore there would be less stress and anxiety to the patient.
Since its introduction mammography has improved women’s lives by detecting breast cancer in its earliest stages decreasing its mortality rates. The efforts of campaigns such as Know Your Lemons have taught women to be self-aware and how to continually monitor their breast health. Mammography began like diagnostic x-ray with screen film mammography capturing images on film and moved to digital full-field mammography imaging allowing for better detections of microcalcifications, breast lesions and other abnormalities. To overcome the limitations of two-dimensional imaging mammography moved to DBT improving the accuracy of diagnosis and detection. By scanning structures in slices, it removes the problem presented by superimposition of breast tissues. Working alongside US, digital mammography and digital breast tomosynthesis have become essential to women’s imaging. The technology has continued to advance with contrast enhanced digital mammography. Making diagnosis and staging of breast cancer more available as well as more affordable. Due to these advancements false positive rates have decreased making routine scanning for women a bit less stressful.
Works Cited
- Badr, S., Laurent, N., Régis, C., Boulanger, L., Lemaille, S., & Poncelet, E. (2014). Dual-energy contrast-enhanced digital mammography in routine clinical practice in 2013. Diagnostic and Interventional Imaging, 95(3), 245–258. doi: 10.1016/j.diii.2013.10.002
- Faridah, Y. (2008). Digital versus screen film mammography: a clinical comparison. Biomedical Imaging and Intervention Journal, 4(4). doi: 10.2349/biij.4.4.e31
- Harvard Health Publishing. (2014, March). Digital mammography better for some women. Retrieved March 9, 2020, from https://www.health.harvard.edu/newsletter_article/digital_mammography_better_for_some_women
- Byun, J., Lee, J. E., Cha, E. S., Chung, J., & Kim, J. H. (2017). Visualization of Breast Microcalcifications on Digital Breast Tomosynthesis and 2-Dimensional Digital Mammography Using Specimens. Breast Cancer: Basic and Clinical Research, 11, 117822341770338. doi: 10.1177/1178223417703388
- Patterson, S., & Roubidoux, M. (2014). Update on new technologies in digital mammography. International Journal of Women’s Health, 781–788. doi: 10.2147/ijwh.s49332
- Breast Cancer Screening (PDQ®)–Health Professional Version. (2019, October 11). Retrieved March 10, 2020, from https://www.cancer.gov/types/breast/hp/breast-screening-pdq
