Digital Breast Tomosynthesis (DBT) is an imaging technology that helps radiologists find breast abnormalities. DBT is a three-dimensional technology that provides thin cross-sectional images through the breast. This technology is designed to prevent overlying structures from obscuring breast masses and intersecting normal structures from being falsely identified as suspicious abnormalities.
In recent years, demand for implementing and using Digital Breast Tomosynthesis technology at women’s centers has grown, which has led to the belief that it’s new. While it may be the latest modality, the Federal Drug Administration (FDA) approved Hologic Dimensions as the first manufacturer of the technology in 2011. The FDA has since approved three more manufacturers: GE, Siemens, and Fujifilm.
What Is Digital Breast Tomosynthesis?
Tomosynthesis is the performance of high-resolution 3D digital images utilizing different angles. DBT utilizes a limited number of angular ranges to create mammography images with depth perception from compiled projection images. Each manufacturer’s machines have different angle ranges.
Is Tomosynthesis the same as 3D Mammography?
Tomosynthesis is synonymous with 3D mammography, allowing technologists to obtain images of the entire breast that provide more information than 2D mammography alone. This means radiologists can more accurately detect breast cancer at earlier stages and reduce the frequency of additional testing.
Breast Tomosynthesis (3D) vs. 2D Mammography
Originally mammography was performed using film screen image processing. Digital mammography replaces conventional film with electronic detectors. Like a digital camera, the images are taken with the tube head at 0 degrees to the image detector. DBT, or 3D mammography, uses a direct or indirect image process with the tube head at different projection angles to take the projection images. These images are comprised of thin, millimeter slices and are then processed with software to create a 3D model with depth perception, allowing for more comprehensive images.
How does Digital Breast Tomosynthesis work?
Digital Breast Tomosynthesis works by taking multiple angled images in an arch motion with the tube head offset from the image detector. The images taken are called projection images. The number of projection images depends on the manufacturer’s technology. The projection images are then processed by computer software, and the 3D tomosynthesis images are created with a DBT volume set. The number of images depends on the thickness of the breast and the slice thickness programmed per manufacturer. This technology gives the radiologist more information to guide the detection of breast abnormalities. Documented clinical studies have proven that utilizing a combination of 2D and 3D imaging has increased the percentage of breast cancer detection and improves the specificity of mammography.
Radiation Dose During Breast Tomosynthesis
Per FDA guidelines, radiation dosage in mammography must be kept very low, no more than 300 mrads or 3 mGy per view. Depending on the filter and anode material combination on a unit, a patient can expect an average of 1.2 mGy of radiation exposure for 2D mammography and 1.4-1.5 mGy for 3D mammography. When added together, this is below the 3 mGy limit. According to Deborah Thames, MSRS, RT(R)(M)(QM), MTMI instructor & lead technologist at MD Anderson Cancer Center in Houston, Texas, that’s like the equivalent of background radiation you would be exposed to while walking around on the earth for two months.
3D Mammography Pros & Cons
As with any technology, there are benefits and drawbacks. Deborah Thames provides an insider’s perspective on some of the pros and cons of Digital Breast Tomosynthesis.
Pros
3D digital mammography separates superposed tissue into 1-2 millimeter slices, according to the unit’s technology. So, for example, if the breast is five centimeters thick, the software will provide the radiologist with 50 images. In conventional 2D mammography, those images would all be one with superimposed breast tissue, potentially hiding pathologies.- With 3D mammography, the radiologist can more easily see within these individual slices and be assured that it’s normal tissue reducing false positive readings, improving the specificity of the mammogram, and reducing the need for breast biopsies.
- The reduction in false positive readings means the recall rate for patients is lowered, reducing unnecessary patient anxiety.
- Edge depiction is improved with Digital Breast Tomosynthesis, meaning the radiologist can see a lesion as a whole and accurately measure it. This improves their ability to differentiate large index masses and small, non-index masses scattered around them. It also helps prepare the patient for additional breast modalities such as ultrasound, MRI, or molecular breast imaging. Having accurate measurements allows an oncologist to determine what stage of breast cancer the patient has to provide the correct treatment of surgery, chemo or radiation therapy.
Cons
- There is a longer learning curve for the radiologist for the reading of the DBT breast exam. All personnel involved, radiologists, medical physicists and mammography technologists are required to have 8 hours of DBT training.
- It can be challenging to adjust to detecting abnormalities in one-millimeter slices, especially calcification that can have different distributions in the breast which are now separated by the slices in the software. There are also more images for the radiologist to look at, meaning the process can be more time-consuming.
- One of the ways that abnormalities “pop” on mammography images is the brightness level, but the brightness of the images in 3D mammography is much lower than with 2D mammography. It can take a while for a radiologist to adjust to recognizing abnormalities accurately without this tell-tale brightness to grab their attention.
- Some DBT units, depending on the manufacturer, may require more space due to the angle that the tube moves.
- There are additional costs associated with DBT units, including facility accreditation, increased inspections, and more quality control testing.
- The potential for an increase in breakdowns of components means an associated increase in visits from field engineers. This can mean an increase in downtime of equipment as well as maintenance contract costs.
Cost of DBT
The cost associated with DBT units varies based on the age of the technology, manufacturer, and the service contracts facilities enter with the manufacturers. The price of the units can range from $85K - $275K, based on age and manufacturer. Further complicating the cost issue, the “best” mammography system differs for every facility, depending on factors such as practice goals, patient volume, and budgets.
One potentially prohibitive cost for some facilities isn’t even the DBT unit itself but the space in which the unit will be housed. As previously mentioned, DBT units need more space for the C arm that arcs from side to side over the patient. A major renovation will be necessary to accommodate the addition if a facility currently lacks the space for such a large machine.
To perform mammography in the United States, mammography facilities must be accredited & certified every 3 years by an FDA approved accrediting body. Each facility is responsible for paying for these expenses. Deborah Thames’ facility has 17 units, and the first unit costs $1700 with a price reduction for additional units for ACR accreditation. Along with the ACR, there are 2 states that are also FDA approved accreditation bodies, the states of Texas and Arkansas. Breast centers in those 2 states can choose if they want to use the ACR or their own state as their accrediting body. All other states in the United States must use the ACR. The ACR and 2 state accreditation bodies may have different costs associated with accreditation. In addition to ACR accreditation, all mammography breast centers in the United States need to pass an annual MQSA inspection to be certified for the next year. There are also costs associated with MQSA inspections that have to be paid.
After purchasing the unit and ensuring there is space for it, facilities also have to pay to keep the machines in working order, which can be quite costly. While an imaging center may enter into a service contract with their manufacturer, many facilities choose to have a field engineer on-site, especially in larger practices with multiple machines that could break down at any time. Mammography facilities must also employ a medical physicist to monitor the machines and conduct an annual medical physicist survey.
Why Mammographers Need Digital Breast Tomosynthesis Training
Under the U.S. law called the Mammography Quality Standards Act (MQSA) technologists must have 8 hours of training in Digital Breast Tomosynthesis (DBT) before they will be able to perform mammograms on 3D mammography machines, without supervision. Most breast centers now have 3D mammography machines so they will need to have this training in Digital Breast Tomosynthesis before they will be able to use that machine for performing 3D mammograms. While the FDA’s Division of Mammography Quality Standards (DMQS) recognizes there are some features that are unique to each specific DBT system, personnel need only obtain training on one DBT system, or general DBT training, to meet the new modality training requirement. DBT technologists are encouraged to pursue additional training on their particular unit(s) to be as familiar as possible with their functionality.
Training is necessary for radiologic technologists to properly understand the technology they are working with. They need to be able to maneuver the console screen commands, understand the theory of DBT, and learn the unique features of the facility’s unit.
How to get DBT Certified
Mammographers can obtain their eight hours of DBT training for certification in various ways. The four manufacturers have training consultants who can train mammographers on their specific units.
There are also Continuing Education Instructors with DBT qualifications who can offer:
- In-person courses
- Webinars
- On-demand
- Peer-to-peer training by MQSA certified technologists
Whatever form of training a mammographer or radiologic technologist pursues, the individual providing the training must be a qualified instructor, defined as an individual whose training and experience adequately prepare them to carry out specified training assignments. At the end of the training, personnel must be able to provide documentation demonstrating eight hours of training. Documentation may include:
- letters
- certificates
- documents from manufacturers or formal training courses
- confirming letter from a Continuing Education Unit granting organization
- attestation about experience.
MTMI Mammography Courses
Medical Technology Management Institute (MTMI) has several mammography training courses you can take to learn about Digital Breast Tomosynthesis. If you are a technologist just starting in the field, our initial mammography training course includes an optional 6th day devoted solely to DBT training. Alternatively, our single-day DBT training course is offered independently for those already familiar with mammography practice.
MTMI programs are taught by experts with national reputations in their fields and cover every modality. Our cross-training courses are offered in the classroom and via webinars and prepare you for registry exams, accreditation, and to take your career to the next level. Check out our full catalog of programs, or contact us with questions today!