Breast Imaging: Current Trends and Future Applications

Terry Duggan-Jahns, RT(R)(CT)(MR)(M)
*Manager, Outpatient Diagnostic Imaging, St. Joseph Medical Center, Tacoma, Washington. Address correspondence to: Terry Duggan-Jahns, RT(R)(CT)(MR)(M), Manager, Outpatient Diagnostic Imaging, St. Joseph Medical Center, 1717 South J Street, Tacoma, WA 98401. E-mail: tdugganjahns@mac.com.
Breast cancer is the most common cancer in women after skin cancer; 1 in 7 women will be diagnosed with breast cancer in her lifetime. The American Cancer Society (ACS) estimates that there are 213 000 new cases per year and that the disease accounts for 41 000 deaths per year in the United States. Of these new cases, the ACS estimates that only 63% will be diagnosed at the localization stage when the survival rate is 97%.1 Recent advancements in breast imaging technology have improved the ability to find breast cancer earlier when it is most treatable, helped to distinguish cancerous lesions from benign lesions, shown the true extent of the disease for surgical and therapeutic planning, and assisted in the treatment and follow-up management of patients with breast cancer.
Analog (Film-Screen) MammographyMammography imaging technology debuted in the late 1960s and remains the gold standard for breast cancer detection today. Mammography imaging technology can reliably image calcifications, which are often associated with early stage breast cancers such as ductal carcinoma in situ. The decline in mortality for breast cancer has been attributed to early detection through screening mammography and improved therapy. Age 40 is the recommended age for breast cancer screening and, because of the growing population of women over 40, every year more women are getting annual mammograms, according to the National Research Council.2
Full-Field Digital MammographyPublished in the New England Journal of Medicine in October 2005, the Digital Imaging Screening Trial found that digital mammography is a better imaging tool and more accurate than conventional film mammography in: (1) women under the age of 50 years; (2) women who are premenopausal or perimenopausal of age; and (3) women with radiographically dense breasts.3 The examination time is decreased and it provides the radiologist with higher quality images than analog film-screen mammography. Most mammograms are still performed on analog systems. It is estimated that less than 10% of all mammograms currently use digital mammography technology, but its availability to patients is expected to increase in the future.3
Magnetic Resonance Imaging Magnetic resonance imaging (MRI) of the breast was approved in 1991 by the US Food and Drug Administration (FDA) as a supplemental tool to mammography to aid in the diagnosis of breast cancer.4 It is the second fastest growing MRI procedure in the United States. MRI is considered a problem-solving technology, especially for patients with very dense breasts, those who have suspected lesions found on mammography or ultrasound, and patients with augmented breasts. It is highly sensitive to small abnormalities that can sometimes be missed with other breast imaging techniques. It can also help determine the type of surgery (lumpectomy or mastectomy) indicated when breast cancer is found. There are limitations with MRI because it cannot image calcifications, which are tiny calcium deposits that can indicate breast cancer.
Historically, MRI breast imaging guidelines were as follows4:
Suspicious mass found on mammography and ultrasound imaging
Positive axillary nodes—negative mammograms and ultrasound-unknown primary
High-risk factors—known BRCA1 or BRCA2 genetic mutation
Extremely dense breasts—on mammography
Staging/treatment planning-known cancer—bilateral study; 5% will have contralateral involvement
Management of known breast cancer—follow-up chemotherapy or radiation therapy
Implant rupture, implant integrity
For women at average risk, the ACS recommends getting annual mammograms and breast examinations by a physician, beginning at age 40. The ACS recently recommended that high-risk women should begin getting MRIs and mammograms at age 30.5
The new guidelines for MRI breast imaging published by the ACS recommends MRI breast screening of high-risk patients, in addition to mammograms for women who meet at least 1 of the following criteria:
BRCA1 or BRCA2 mutation
First-degree relative (eg, parent, sibling, or child) with a BRCA1 or BRCA2 mutation, even if they have yet to be tested themselves
Lifetime risk of breast cancer scored at 20% to 25% or greater based on one of several accepted risk assessment tools that look at family history and other factors
Radiation to the chest between the ages of 10 and 30
Li-Fraumeni syndrome, Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, or a history of one of these syndromes in a first-degree relative
The disadvantages of MRI breast imaging are that it remains an expensive imaging modality and it is not always readily available.
Click here to see MRI breast images
Magnetic Resonance Imaging-Guided Breast BiopsyMRI-guided breast biopsy vacuum-assisted technique has been proven to be a beneficial and successful option if a lesion cannot be identified or is not visible on ultrasound. This technique can be expensive because specialized equipment is needed and well-trained users are absolutely necessary.
Ultrasound and Ultrasound-Guided BiopsyUltrasound is increasingly being utilized to image the breast and guide biopsies (core and fine needle) of suspected breast cancer. It has excellent contrast resolution. Ultrasound is frequently used to evaluate breast abnormalities found on screening mammograms, diagnostic mammograms, or a physician-performed clinical breast examination. It can differentiate between solid and cystic lesions or lymph nodes. Limitations of ultrasound include a lack of good spatial resolution, its effectiveness is operator dependent, it cannot reliably detect calcifications, and the whole breast cannot be imaged at one time.
Breast-Specific Gamma ImagingBreast-specific gamma imaging (BSGI) is a functional imaging technique designed to assess changes in tissue function rather than in anatomical structure. It is most commonly used for patients who have equivocal mammography or ultrasound findings. It is also used to help determine the extent of breast cancer involvement and to help clarify lymph-node involvement.6 The breast is compressed between 2 camera heads and a small dose of radioactive material is injected intravenously (Sestamibi). BSGI is capable of helping to differentiate cancer from other structures.
Computer-Aided DetectionComputer-aided detection (CAD) technology uses a computer to provide a second read or assist radiologists in making an accurate diagnosis. CAD systems have been approved by the US FDA for use in mammography, lung computed tomography, virtual colonoscopy, and breast MRI. CAD systems for mammography became commercially available in June 1998. They help increase the sensitivity for detecting small lesions and calcifications in the breast. CAD systems used in MRI allow the radiologist to view up to 2000 images at one time. After the injection of contrast material and dynamic imaging, these systems color code the enhancement kinetics of various tissue areas of the breast. CAD systems help analyze enhancement patterns of tumor angiogenesis of invasive tumors versus normal fibroglandular tissue.
The Future of Breast Imaging: Where Are We Going?The following are new technologies that are emerging in breast imaging:
MRI breast spectroscopy—The June 2006 issue of Journal of Radiology reported on a preliminary study by Memorial Sloan-Kettering Cancer Center in New York about the potential of using MRI breast spectroscopy. Researchers found that patients with proven positive biopsies had an elevated choline marker on magnetic resonance spectroscopy imaging mapping. This study also indicated the potential of utilizing magnetic resonance spectroscopy to eliminate the need for conventional breast biopsy techniques in the future.7
Positron emission tomography (PET) imaging, PET mammography (PEM), and PET/CT—These are currently the most useful noninvasive tests for staging or restaging breast cancer and monitoring metastatic disease throughout the whole body. A few research centers across the country are evaluating dedicated PEM devices that may potentially improve the identification of small breast cancers.8 This technology has the potential to detect breast cancers as small as 2 mm. Additionally, new PET targeting agents other than fluorodeoxyglucose are currently being developed.
Digital breast tomosynthesis (DBT) is an emerging imaging technology that is a cross between mammography and CT, which provides a 3-dimensional, digital X ray of the breast. This imaging technology allows the radiologist to look at slices or individual layers of the breast. DBT takes multiple X-ray pictures of each breast from many angles. The goal is to overcome patient discomfort from compression, detect cancer hiding within overlapping tissue, and reduce the number of views needed. Early results with DBT have shown promise. Researchers believe that this new breast imaging technique will make it easier to see breast cancers in dense breast tissue and make breast screening more comfortable.9
Breast Imaging Informational Web Sites
http://www.breastcancer.org/
http://www.cancernews.com/
http://www.cancer.org/
http://www.womenshealth.gov/
ConclusionsContinuously emerging advancements in breast imaging technology present new challenges and possibilities for the field of radiology. Such innovations in technology are helping clinicians detect and diagnose breast cancer in its earliest stage, thus saving the lives of countless women yearly. Recent revision of ACS breast cancer early detection guidelines for MRI breast imaging have been a critical step for screening of high-risk patients.
As the population of women over the age of 40 continues to grow, it will create more of a demand for breast imaging. There will also be more of a demand for highly trained, dedicated, experienced, and skilled radiologists and technologists to specialize in this imaging arena. Currently, there is a shortage of breast imagers. The Institute of Medicine and the National Research Council report that there are approximately 20 000 radiologists in the United States who can interpret mammograms, but only 2000 actually subspecialize in the field of breast imaging. The American Registry of Radiologic Technologists Web site reports that there are 47 384 technologists with advanced certification in mammography imaging.2 These glaring statistics beg the question: Will we be prepared to accept the future challenges presented to us?
References1. American Cancer Society. Available at: http://www.cancer.org/. Accesssed November 13, 2006.
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4. Imaginis. Breast cancer diagnosis. Available at: http://www.imaginis.com/breasthealth/mei.asp. Accessed November 13, 2006.
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9. Breastcancer.org. Digital tomosynthesis. Available at: http://www.breastcancer.org/digital_tomosynthesis.html. Accessed November 13, 2006