Breast Imaging Essentials

Transcription

1 Breast Imaging Essentials Module 10 Transcript 2016 ASRT. All rights reserved.

2 Breast Imaging Essentials Module 10 Digital Breast Tomosynthesis 1. ASRT Animation 2. Welcome Welcome to Module 10 of Breast Imaging Essentials Digital Breast Tomosynthesis. This module was written by Stephanie Johnston, M.S.R.S, R.T(R)(M)(BS)(BD) 3. License Agreement 4. Objectives After completing this module, you will be able to: Describe the digital breast tomosynthesis system. Explain the origin and theory behind tomosynthesis exams. Visualize the acquisition and display of DBT images. Discuss the benefits and challenges of this modality for both patients and staff. Define the similarities and differences of digital breast tomosynthesis and standard imaging. Differentiate current FDA approved units and their features. Recall QC tests and radiation dose specific to DBT. Explain the storage, distribution, and compatibility of DBT images. Recognize the training and certification requirements for DBT. 5. Tomography Tomography is not a new technique in radiology. It has been used in conventional x-ray since the 1930s. The exams were used to concentrate on a specific plane of interest, while blurring out structures on either side of that plane. This focus enhanced radiographic contrast relative to the blurred areas for exams of select body parts. Tomography of the head was performed to evaluate the orbits or facial bones. Ear exams studied the middle and inner ear within the petrous pyramids. When tomography of the spine was ordered, the exam was performed to better view the difficult-to-see odontoid process or upper thoracic spine. Tomograms of the chest often provided images of the sternoclavicular joints and the sternum free of superimposition from adjacent anatomical structures. In addition, abdominal tomography was performed to assess the renal system including the kidneys, ureters, and bladder or the biliary system, specifically the bile ducts. 6. Tomography Tube Movement During tomographic imaging, the X-ray tube moves synchronously with the image receptor to acquire images. These images could be acquired using several different movements of the tube, such as linear, circular, and elliptical patterns. Hypocycloidal and trispiral also are tube movements used for image acquisition. Linear tomography was the most widely used movement. 7. Linear Tomography To acquire tomographic images, the patient remains in a stationary position while the x-ray tube moves in an arc in one direction, while the image receptor moves simultaneously along a straight line in the other direction. The movement of both tube and receptor are calculated to place the area of interest at the exact center point of the tube and receptor. In tomographic imaging, the plane of interest appears in focus on the image, because it was the only plane of the subject that both tube and receptor were constantly aligned with throughout the exam. Because all other parts of the subject were only partially imaged, they remain out of focus, allowing the physician an unobstructed view of the area of interest. The region of interest can be changed by altering the arc of the tube and the movement of the receptor. 8. Tomographic Planes Due to the thin cross-section produced by the resulting image in tomography, the plane of interest is also called a cut, or slice. The thickness of the slice is determined by the angle of the tube s arc. A greater arc of the tube results in a thinner slice, with a more focused region of interest. A smaller arc of the tube

3 results in a thicker slice, with a less focused region of interest. In the early days of tomographic imaging, its primary disadvantage was an increase in patient dose. Because the tube was energized during the entire movement period, which could be several seconds long, a patient s total dose could have reached several rad by the end of the exam. 9. Modern DBT Tomosynthesis has since improved on the old linear tomography method by allowing a number of infocus planes to be generated from the sequence of images acquired during the arc of the tube. Similar to older methods, the patient is placed in a stationary position while the tube moves in an arc across the breast. However, during modern tomosynthesis, the image receptor is stationary or tilts slightly with the tube, so images are acquired in multiple planes which can later be reconstructed. These low dose tomographic images acquired on a digital mammography system are the first step in digital breast tomosynthesis. 10. History of Tomosynthesis Tomosynthesis for breast imaging was developed in the 1990s by a group interested in improving breast imaging and detecting breast cancers at an earlier stage. The team dedicated to perfecting tomosynthesis breast imaging consisted of doctors Daniel Kopans, Loren Niklason, and Laura Niklason. Their patent for this technology was filed in the United States Patent office on July 22, Inventors of DBT Dr. Loren Niklason is a medical physicist who joined Hologic in 2005 as the Director of Tomosynthesis Programs. Dr. Laura Niklason is a Professor of Anesthesia and Biomedical Engineering at Yale. Dr. Daniel Kopans is a professor in the department of radiology at Harvard Medical School and the director of breast imaging at Massachusetts General Hospital. Their collaboration led to this new breast imaging technology, and on February 16, 1999, patent number 5,872,828 was issued to their invention. It was not until 2011 that the first digital breast tomosynthesis unit was approved for use on patients for breast imaging. 12. Knowledge Check 13. Knowledge Check 14. Digital Breast Tomosynthesis (DBT) Digital breast tomosynthesis, or DBT, is a new imaging modality that is also sometimes referred to as 3D Mammography, or just Tomo. It can be used for screening and diagnostic breast imaging. DBT is a replacement for full field digital mammography, or FFDM systems, and computed radiography, or CR. This technology can acquire images in 2D mode, tomosynthesis mode or a combination of the two modes. Digital breast tomosynthesis technology improves the detection and characterization of breast abnormalities, because it subtracts overlapping structures from the image of the breast. DBT is a full field digital mammography exam using a system that is designed to acquire information in a specific format and reconstruct images for display and interpretation by a radiologist. Digital breast tomosynthesis can be used for both screening and diagnostic mammography exams. 15. Digital Breast Tomosynthesis Upgrade Digital breast tomosysthesis is not just a software upgrade to existing digital units, and cannot be used on cassette-based or CR systems. However, some FFDM units may only require a platform upgrade. These upgradeable units are FFDM systems that were purchased with the intent of adding the tomosynthesis mode at a later date. This can be accomplished by adding software and hardware to an existing, FDAapproved digital unit, so it can work in DBT mode. In most cases, adding digital breast tomosynthesis capabilities requires replacement with a new unit. If the facility already has 2D digital systems it will also be necessary to upgrade the physician interpretation workstation and the short and long term data storage systems will also be necessary. If the facility is not currently a digital facility, these components will need to be added at the same time as a DBT unit to be able to interpret and store the digital images. 16. DBT Classification

4 Because digital breast tomosynthesis is considered a new breast imaging modality by the FDA, it involves additional DBT-specific training requirements. Staff need this training in order to perform and interpret the exam. The medical physicist who performs the Mammographic Equipment Evaluation, or MEE, and conducts the annual survey on the equipment will also need additional training. There are also certification and accreditation requirements for DBT. Most digital breast tomosynthesis units look very similar to standard 2D units although the machine operates differently during tomosynthesis mode. 17. Image Processing Specialized computer software allows these images to be quickly reconstructed into the form of a threedimensional breast, in the same way reconstructed CT images are produced. With new software and DBT imaging technology, the radiologist can scroll through slices of breast tissue and be able to see small, unobstructed objects within the breast. Subtle differences in adjacent breast tissue are better visualized, and the problem with tissue overlap is virtually eliminated. 18. Stacked Images An easy analogy to describe the reconstructed DBT image is to compare it to a stack of playing cards. In this analogy, a whole stack of cards represent the entire breast. During the arc movement of the unit, a stream of visual information is obtained and sent to the review station. This information is then reconstructed into a series of distinct two-dimensional images, which are kept in the order they were acquired. This stack of two-dimensional images represents the entire three dimensional breast. Each card, or slice, can be viewed individually in 1mm increments. The number of slices is dependent on the thickness of the breast. A 6mm compressed breast will have six 1mm slices in the reconstructed breast image, which can be viewed individually or in order. The 6mm breast has six images stacked up. Scrolling through the breast images, the radiologist can see abnormalities toward the bottom of the stack without interference from other tissues in the way. During interpretation of DBT, the radiologist has the ability to scroll to the exact slice that best displays an abnormality and report any abnormalities accordingly. 19. Knowledge Check 20. Knowledge Check 21. Parallax Taking a 3D object and displaying it in a 2 dimensional manner is the basis of digital breast tomosynthesis. DBT imaging is made possible due to unique image acquisition based on parallax. Parallax is the perceived displacement of an object when viewed from a different angle. Look at the X on the monitor. Continue looking at the X and cover one eye. Quickly change to the other eye and repeat several times. The X appears to move slightly side to side as you change eyes. This is a parallax shift and is how digital breast tomosynthesis can improve the visualization of breast tissue. 22. Changing Angle Multiple images of the stationary, compressed breast are acquired at different angles during the arc of the tube. After all of the individual images are obtained, they are reconstructed and displayed as a collection of slices. The arc shift in imaging avoids most overlap of breast structures in the reconstructed images of the breast. Displaying the breast in this manner increases the capability of the radiologist to see small abnormalities in the breast that may have been superimposed with other breast structures on standard mammograms. 23. DBT Acquisition During acquisition in standard mammography exams, the breast is compressed and a single image is acquired. For a screening exam, this is done four times; twice on each breast in craniocaudal and mediolateral oblique views. During DBT acquisition, the patient is positioned just like the 2D acquisition. The difference is that the tube moves to acquire multiple quick, low-dose images. A standard 2D image may also be acquired while the patient is in the same compression. After each image acquisition

5 sequence in either 2D or tomosynthesis, the technologist is still required to do an initial check to ensure that all the breast tissue is present, positioning is optimal, and that the quality of the image is satisfactory. If the image is acceptable, the technologist will move on to the next view. 24. Multi-functional All FDA-approved digital breast tomosynthesis units acquire 2D and tomosynthesis images in a slightly different manner. Each system s image acquisition process is vendor-specific. Each patient imaged using DBT will have both standard and tomosynthesis images taken, depending on the study that is being performed. Although all units have tomosynthesis capabilities, standard 2D breast imaging may be used independently of DBT. 25. Workstation The workstation is not dramatically different in digital breast tomosynthesis. The technologist will still select which view is to be obtained. All of the components of the standard digital workstation are available, such as exposure mode, filter selection, kvp and mas settings, grid in or out, focal spot size, plus or minus density selection, and image outputs. There are minor vendor-specific differences related to DBT functions, usually the display of thumbnails or work lists, but generally the workstation is very similar to the standard digital workstation. As with any FFDM or CR digital mammography system, the DBT workstation is compatible with most radiology information systems or hospital information systems, allowing the technologist to pre-fetch comparison exams and populate their daily work lists. 26. DBT Display The equipment that the radiologist uses to review and interpret screening or diagnostic exams is referred to as the soft copy review station or workstation. At the soft copy workstation, radiologists can view the entire DBT exam of the breast in small stacked layers just millimeters thick. He or she may choose to watch a cine loop or continuous video of those layers with the ability to stop at any time. Some radiologists may choose to scroll one slice at a time. Cine and single slice viewing are accomplished by using a feature on a special mouse. At this workstation, standard 2D images also are available for review and comparison with old studies. 27. Computer Aided Detection With most workstations, the radiologist can easily move to and from the DBT and standard 2D results of the exam during the review process. In some instances, a separate monitor may be necessary to view the reconstructed tomosynthesis image, as the current 2D images are displayed with comparisons on the standard monitor set up. Computer Aided Detection, or CAD, is review assistance software that is used by many radiologists interpreting standard 2D digital images. It can also be used on DBT images, and different versions of CAD systems are compatible with different vendors units. 28. Radiologist s Workstation The standard setup for the soft copy review station is not much different for DBT than for digital mammography. Generally, there are three monitors at each station. The first monitor has no particular specifications and usually displays the work list, patient or exam information, integrates with the radiology information system and includes some type of dictation system. The other two monitors are used to review mammographic images. The DBT reconstructed images can be viewed on these monitors depending on the hardware and system setup. Any monitor used to review breast images must be FDA approved for mammography interpretation and the monitors must have a minimum display capability of five megapixels. These monitors have to be capable of displaying the very detailed information necessary for diagnosis. Occasionally, and depending on the vendor, a third review monitor is used to display the DBT image if the standard two monitor system cannot handle the capabilities of the tomosynthesis scroll and cine functions. The radiologist will establish his or her standard for the hanging protocols based on how they review the images. Hanging protocols are specific to each radiologist and are stored by the system. An individual radiologist s hanging protocol is automatically applied when he or she signs into the soft copy review station. 29. Knowledge Check

6 30. Knowledge Check 31. Patient Benefits with DBT DBT allows for better visualization of overlapping tissue, which is especially beneficial to women with dense breasts or large areas of asymmetry. Better visualization of breast tissue can reduce the need for additional images or recalls that are currently necessary for clarification. With the ability to see the structures of the breast in better detail and without superimposition of other structures, the radiologist can make a final interpretation from the first exam and not have the patient back in for more views. Spot compression or magnification views previously used for clarification and location of an abnormality are recommended less often with DBT because of the improved visualization of breast tissue. This reduction in additional imaging, in turn reduces the radiation dose that would have been incurred during the acquisition of supplemental views. Additionally, because of the decrease in recalls, patients receive their interpretation results faster. This means fewer patients suffer the stress of waiting for final results. 32. DBT Challenges for the Patient For the patient, the DBT exam will not be much different than the standard digital mammography exam. The same four views are obtained, which again includes a craniocaudal and a mediolateral oblique view of each breast, and the breast is still compressed to reduce motion and decrease radiation dose. Basically, the patient will have nearly the same experience as with standard 2D mammography exams except for the tube moving during the exam and being in compression slightly longer than before. 33. Cost and Availability Two things that may differ from standard mammography exams are the costs for the DBT exam and the availability of the technology. Currently, Medicare is the only entity that covers the DBT exam. While other major insurance carriers are expected to follow, it is area-specific and most do not currently cover the costs of a DBT exam. Due to reimbursement issues, many facilities charge a flat fee at the time of service for the DBT exam. Additionally, the DBT technology is not available in all facilities and may not be available in areas near where a patient lives or chooses to have their exam performed. According to the FDA, 98% of mammography units are now digital systems which include all FFDM and CR 2D mammography units plus any DBT being used. Additionally, 97% of facilities are now using digital systems. Even if facilities are using digital systems, there is no guarantee that DBT-enabled scanners are available. It may be challenging for a patient to find a facility that offers DBT exams. So while it is extremely easy to have standard digital breast imaging, it may be more difficult and costly to have a DBT exam. 34. Benefits to the Facility Digital breast tomosynthesis can benefit a facility in several ways. It can be a great time saver for facilities in multiple areas. With the improved technology, fewer biopsies need to be performed on patients, and the facility s cancer detection rate will improve. Marketing options for facilities that offer DBT technology can also benefit the facility. 35. Time Benefits Digital breast tomosynthesis can benefit a facility by saving valuable time. This time savings happens in several areas of a facility. Patients are recalled for supplemental views mainly because of tissue overlap. DBT technology gives the radiologist better information and visualization of breast tissue, and he or she will be able to make quicker final interpretations of DBT mammography exams. This results in a reduction in the number of recalls and the number of biopsies. This saves the facility time, because fewer appointment times are needed for additional imaging, and less time is required for someone to schedule these appointments. Additionally, with fewer recalls, there is a decreased need for personnel to call patients informing them of incomplete results and to track those results. The staff is now freed up to perform other duties. This decrease in inconclusive findings allows the department to avoid unnecessary invasive procedures. Freeing up technologists and radiologists similarly from preventable procedures saves time all around. These time savings give a facility the ability to increase patient throughput.

7 36. Time Loss Learning a new technology takes time. The acquisition of digital breast tomosynthesis images takes a bit longer than with the standard 2D breast imaging. When a facility first begins to use DBT technology, patients scheduled time slots might need to be extended to allow more time for each exam. With the increase in information available to them, radiologists will take longer to interpret DBT exams. This is usually a temporary time loss. Once personnel become comfortable with the technology, these delays will disappear and the facility will benefit from the other discussed time savings. 37. Fewer Biopsies and Improved Cancer Detection An important metric in a breast imaging facility is the cancer detection rate. The detection rate is the number of true cancers found per 1000 exams. Digital breast tomosynthesis allows the radiologist to see breast tissue free of superimposition from other breast structures. The result of this clarification will reduce the need for biopsies that would have previously been performed on questionable 2D abnormalities. DBT technology has reduced the need for negative biopsies, while improving detection of true cancerous abnormalities. This reduction in false positive biopsies and increase in true positives will improve the cancer detection rate for the facility. 38. Marketing Benefits Digital breast tomosynthesis is a relatively new technology for breast imaging. While standard digital imaging is widely used, DBT may not be. For facilities that employ the DBT technology, it may provide some added marketing potential. Although it is not usually the concern of a technologist, marketing opportunities and the increased care to patients should be considered when a facility decides to add DBT to its breast imaging options. The type and duration of marketing can increase the patient load and will likely affect workflow. 39. Knowledge Check 40. Knowledge Check 41. Challenges to DBT Some of the challenges associated with digital breast tomosynthesis include increased costs to facilities. These costs can be incurred in several ways. Changes in workflow will certainly make a difference and could create some challenges for a facility. Each facility may incur the cost for additional training to the technologists performing DBT exams, and possibly for the radiologists that interpret the exams. 42. Costs There will be costs incurred with the addition of digital breast tomosynthesis technology to a facility. These costs might include the implementation of the DBT system; which can include the initial purchase for the equipment or upgrades to existing platforms. Upgrades to the radiologist s workstation and to the current PACS may also be needed. These particular costs are sometimes grossly underestimated. It is beneficial to discuss the upgrade with all involved parties including staff involved with scheduling, billing and coding. Technologists, radiologists, IT personnel, and medical physicists will need to be consulted when planning the upgrade. Fully understanding the costs and necessary improvements will make the transition much smoother. Additionally, when acquiring DBT capabilities, the facility will incur certain other costs. To recap, DBT exams might not be covered by most patients insurance, so facilities will have to determine how to cover the costs for these exams. Many facilities have passed part of the responsibility on to the patient by charging an additional flat fee for DBT exams. Facilities may increase the cost of the exam, while some larger facilities can afford to absorb the costs completely. 43. Workflow Digital breast tomosynthesis exams change the workflow in a facility both for the technologist and for the radiologist. Initially, the technologist will require more time to perform the exam for several reasons. The new procedure must be explained to the patient, especially due to the fact that they will be in compression longer than with standard mammograms. Similarly, the radiologist will take more time to

8 interpret the DBT exam. He or she will not get through the exams as quickly as before because of the addition of the three dimensional breast images, viewing it layer by layer and having older comparisons in a different format. Extra time will be needed to complete the mammography reports. By the second year with DBT, returning patients will know what to expect and the experienced technologist will get through the entire process more quickly. In time the radiologist will get faster, and once they have comparisons in the same format, will speed up the review and interpretation process. 44. Training Employees must complete eight hours of new modality training if they are involved in the acquisition, interpretation, or inspection of DBT exams. This includes technologists, radiologists, and medical physicists. Though new modality training is needed to meet certification requirements, it can be challenging for some facilities to get this training completed. Not only because of costs, as previously discussed, but because individuals might have to take time off work to complete off-site training. If training will be completed on-site, time will have to be scheduled for the training. The facility will have to decide the best way to conduct training to meet the specific needs of the department. There are two options that are typically considered. Option one: training can be performed for every employee at the same time. This requires that no patients are scheduled so the department can shut down during that period of time. Option two: only a few, selected individuals receive the training during the scheduled time. These individuals are generally referred to as super-users. Once the superusers are qualified, they can train other employees at a later date. 45. FDA Approved Systems There are currently only three digital breast tomosynthesis systems approved by the FDA. The first DBT unit approved was the Hologic Selenia Dimensions. This DBT unit was approved on February 11th of The GE SenoClaire was the second DBT unit to be approved by the FDA. It was approved on August 26th of The third system to be approved by the FDA was the Siemens Mammomat Inspiration. It was approved on April 21st of Similar Features The previously mentioned approved digital breast tomosynthesis units share many features. All three DBT units have the capability for both 2D and tomosynthesis image acquisition. All DBT units also use an arcing motion of the tube during acquisition, though they vary in the degree and movement of the arc. A larger face shield and extended paddle might be necessary for some DBT units. These features keep the patient s face and the edge of the paddle out of the x-ray field during the tomosynthesis acquisition. The detectors are very similar in size ranging from 24 cm by 29 to 31cm. There is just a 2 cm difference in the three units. Each unit has a slight tilt to the internal aspect of the image detector to accommodate the arc motion, but it is not seen during the exposure. Despite these similarities, each of the approved digital breast tomosynthesis systems has many unique features, as well. 47. Hologic Selenia Dimensions The Hologic Selenia Dimensions was the first digital breast tomosynthesis unit to be approved for use in mammography, and can acquire images in 2D mode, tomosynthesis mode or a combination of both modes. The Dimensions unit is a full-field, direct capture mammography unit. It uses a tungsten target and an aluminum filter combination for both modes of imaging the breast and does use a grid. If tomosynthesis imaging is not recommended or necessary for an exam, 2D breast imaging only may be performed with the Dimensions unit. The patient is positioned for each view, bilateral craniocaudal and mediolateral oblique views, and fully compressed as in standard mammography. 48. Hologic Arc All digital breast tomosynthesis units employ arc motion for the tube head during acquisition. This is where each of the units differs. The arc motion for the Hologic unit is 15 degrees. The tube rotates from degrees to +7.5 degrees. During this continuous motion, the unit acquires a sequence of 15 images, one from each degree of the angle. At the end of the arc sweep, the tube returns to the stationary perpendicular setting and acquires a standard image in 2D mode. Once both 2D and tomosynthesis

9 acquisitions are complete, the patient is released from compression. At this point the technologist can review the image, perform the quality check for positioning and completeness, and accept the set of images before moving on to the next view in the acquisition process. This same process is used for all four standard screening views. For a diagnostic breast imaging exam, the same process can be used for any of the supplemental views. 49. Hologic C-View Hologic also has an additional software upgrade called C-View. This allows for computer generation of the 2D views, both craniocaudal and mediolateral, from information acquired during the tomosynthesis mode, eliminating the extra 2D exposures. Not only does this lower the radiation dose to the patient, but it releases the compression sooner, making the exam more tolerable. This additional software upgrade works on the Dimensions unit and was approved by the FDA on May 16th, The Hologic System The chart shows some of the features of the Dimensions system. 51. GE SenoClaire The GE SenoClaire was the second digital breast tomosynthesis system to be approved by the FDA. The SenoClaire unit is a full field, indirect capture system. The SenoClaire system uses both molybdenum and rhodium targets, and molybdenum and rhodium filters and does use a grid. The SenoClaire system selects the best target and filter combination based on the breast thickness and composition of the patient. Similar to the other DBT units, screening and diagnostic studies to include the supplemental views can be performed, and 2D breast imaging can also be done independently. The biggest difference with the GE SenoClaire is the addition of the Motorized Tomosynthesis Device or MTD. The technologist must replace the 2D detector for the 3D MTD. This allows the existing 2D unit to be used in 3D mode and allow facilities to transition to 3D in a less costly manner. The MTD is removed to return to 2D mode. The SenoClaire system only requires tomosynthesis acquisition on the mediolateral views of each breast. The craniocaudal views are not acquired in tomosynthesis mode. Both craniocaudal tomosynthesis views are reconstructed for the radiologist on their soft copy workstation. This unique feature of the SenoClaire system was developed in order to reduce the radiation dose to the patient during the examination. 52. GE Arc During the mediolateral oblique image acquisition, the tube on the SenoClaire unit rotates in a 25 degree arc. It moves from degrees to degrees. The SenoClaire system acquires nine images during the arc, in what is called a step and shoot method. This means that the tube actually stops moving, acquires an image, and then proceeds to the next stop. Images are acquired at distinct stops throughout the arc rather than during the continuous movement of the tube. Once the 2D and tomosynthesis acquisitions are complete, the technologist can review the image, perform the quality check for positioning and completeness and accept the set before moving on to the next view in the acquisition process. 53. The GE system compared to Hologic This chart shows the comparison of the Dimensions and SenoClaire systems. Notice with the SenoClaire the degree of the arc is greater, but the number of images is fewer. The SenoClaire also stops at each acquisition point where the Dimensions uses continuous motion during acquisition. 54. Siemens Mammomat Inspiration The Siemens Mammomat Inspiration was the third digital breast tomosynthesis system approved by the FDA. The Inspiration unit is a full-field, direct capture system. The Inspiration system uses a tungsten target and a rhodium filter. As with both of the other units, screening and diagnostic studies to include the supplemental views can be performed with the Inspiration system and images are only acquired in the 2D mode if necessary.

10 55. Siemens Arc A bit different from the other two digital breast tomosynthesis units, the Inspiration tube rotates in a 50 degree arc from -25 degrees to +25 degrees. The unit takes 25 images in a continuous sweep. The patient is positioned and compression is normally applied. The Inspiration unit acquires its first image at the 0 degree station, which doubles as the standard 2D image. It then rotates to the -25 degree station and continues with the acquisition of 25 tomosynthesis images before releasing the patient from compression. Once the 2D and tomosynthesis acquisition is complete, the technologist can review the image, perform the quality check for positioning and completeness, and accept the set before moving on to the next view in the acquisition process. As with the Dimensions unit, 2D and tomosynthesis images are acquired in both the craniocaudal and mediolateral oblique views of each breast during continuous compression. 56. Siemens Functions The Siemens Inspiration system uses proprietary OpDose and OpComp functions. OpDose allows the system to select the lowest optimal dose for the patient based on the thickness and composition of the breast. OpComp allows the system to automatically apply compression as long as the breast is soft and pliable, and stops itself at optimal compression. 57. FDA Approved Systems This chart shows all three FDA approved digital breast tomosynthesis systems and some of their specific features. While all three of these units perform digital breast tomosynthesis image acquisition, by comparison they are all slightly different. 58. Other DBT units The new digital breast technology has other vendors working to get their products released. Philips, PlanMed, and Giotto are all working on tomosynthesis breast imaging and hope to have units approved by the FDA and in circulation soon. As with standard digital mammography systems each will have vendor-specific features. Each manufacturer will also determine specifications for quality control and quality assurance. Training will be required for the unique features of the units. 59. Knowledge Check 60. Knowledge Check 61. DBT and Radiation Dose The Mammography Quality Standards Act, or MQSA, set strict dose requirements for mammography many years ago, when film/screen mammography was the only modality. The dose requirement limited one CC view to below 300 mrad. With the establishment of digital mammography, this standard has not changed, and the FDA reported that the average dose for 2D digital mammography units is approximately 15% less than for film/screen mammography. That standard also has not changed with the implementation of digital breast tomosynthesis. The dose requirement for one view of the tomosynthesis mode must not exceed 300 mrad. The multi-image process in the tomosynthesis mode must fall below this established guideline. For that reason, each manufacturer s unit has perfected their target and filter combination, detector material, number of images acquired, and other factors so as not to exceed this threshold. 62. Quality Control The first step in quality control for a digital breast tomosynthesis unit is the Mammographic Equipment Evaluation, or MEE, sometimes called the acceptance test. This is the initial test performed on a unit at installation to ensure that the unit is functioning within the manufacturer s recommendation. This test also establishes the baseline criteria for all future quality control tests performed on the unit. The MEE is a more extensive survey than the annual facility survey performed by the medical physicist. The MEE must be completed by a qualified medical physicist and submitted to the FDA prior to performing any exams on patients. 63. QC Tests

11 As with 2D digital mammography, the quality control for DBT is based on the manufacturer s specifications. This includes the tests to be performed, the frequency of the tests, the guidelines for establishing control criteria, and the corrective action for any test failure. These tests might have similar names and tools for measurement as older tests, however, all DBT units must have quality control tests in the tomosynthesis mode for the phantom, detector calibration, artifact evaluation, and detector uniformity tests. These tests will need to be performed by the technologist on a regular basis and the technologist must document the results. With all three approved DBT units, tomosynthesis tests are usually completed at the same time as the 2D test. When the phantom is in place for the 2D QC, the tomosynthesis phantoms are usually also acquired. Testing does take a few minutes longer with DBT units. 64. Physicist QC for DBT The medical physicist can acquire the tomosynthesis quality control tests at the same time the 2D tests are done. The medical physicist is still required to do an annual mammography facility survey. This survey must include the 2D standard digital mammography survey and additional tests in tomosynthesis mode. Even though they may be acquired at the same time, there are separate measurements for both modes. These tests may have the same names and use the same tools. The facility s quality control and quality assurance program summary must be submitted within 30 days of the survey. 65. Image Storage and PACS After imaging, the entire DBT study is sent to the PACS for storage. If there are two exams, a standard 2D exam and a tomosynthesis exam, they are usually co-registered and stored together. The greatest storage challenge for DBT images is the size of the files sent to the archive. Due to the incredible detail on the images, standard digital mammography files are very large, ranging from 8.8 to 52 megabytes per view. A standard four view mammography study can be just over 200 megabytes. DBT files are even larger, sometimes as much as five times larger per image. The MQSA has specific image retention requirements that still apply to DBT studies, so over time this can create issues with inadequate storage space. DBT files are extremely large, and it takes longer for that amount of information to transfer. Storing and pre-fetching a DBT exam can take 3-5 times longer than standard 2D digital mammography exams. Telemammography of DBT exams will take longer as well. 66. DICOM Compatibility There are some inconsistencies between the different manufacturer s equipment, the soft copy review stations and the storage systems related to the digital image. To standardize this information, a Digital Imaging and Communication in Medicine, or DICOM, header is attached to every image. However, each manufacture interprets the guidelines for the use of the DICOM header slightly differently. These slight differences can cause problems with compatibility from different vendors. Still other vendors have proprietary software and storage that does not use the DICOM format. 67. DICOM Format The DICOM format should be used for any digital breast tomosynthesis image. DICOM allows medical images and information to be easily moved within a facility s internal network. Images will need to be moved between the acquisition workstation, soft copy workstation, PACS storage, and various outputs such as printers or compact discs. DICOM format also allows for the images to be moved via telemammography. Incompatible file types can become a problem if the patient s digital mammography study has to be transferred to another facility for comparison and the images are not in a DICOMcompatible format. 68. Image Distribution DBT images are often distributed to multiple locations. Where the images are sent is dependent on the setup of the facility and whether or not they must be sent to internal or external users. The exact destination order also is dependent on each facility and the equipment vendor used. After acquisition of the images, they might be transferred to the soft copy workstation and PACS. This may be the same location if the facility is set up to have the radiologist read from the PACS. Otherwise, the soft copy workstation may be a separate destination than PACS storage. Prior breast images may be pre-fetched

12 to the workstation from radiology or hospital information systems for comparison. In some facilities this pre-fetching may be a manual process. 69. Educational Requirements for DBT According to the FDA, digital breast tomosynthesis is considered a new breast imaging modality and therefore requires eight hours of new modality training for all personnel related to the new modality. This training is required for all technologists that will acquire DBT images, all radiologists that will interpret DBT exams, and all medical physicists that will perform the annual survey on the DBT equipment. 70. Training from Vendors Typically, some or all of these new modality training hours are provided by vendors with the purchase of the new equipment, and may include training for the technologist and the radiologist. This usually applies to facilities that are completely replacing digital units and facilities that are upgrading a current digital mammography platform to include the tomosynthesis mode. New modality training for the physicist may or may not be covered by the vendor, however the physicist must have the training prior to performing the Mammography Equipment Evaluation and the annual survey on the new equipment. 71. Technologist Training When new DBT equipment is purchased, a vendor-specific applications specialist usually spends several hours training technologist on the new modality, and then awards certificates to the technologists upon completion of the training. The applications specialist must be a qualified individual, usually an employee of the vendor, with the knowledge to teach the technologist how to properly use the new equipment. These individuals also supervise the technologist during the performance of the tomosynthesis exams. The applications specialist must have prior approval to administer continuing education for the new modality. 72. Other Training Sources New modality training can be obtained through a short course, which is usually a weekend seminar through a private entity. These can sometimes be costly to travel to, and may or may not have equipment for hands-on training. New modality training can also be obtained through online educational courses. Online courses eliminate the costs of travel, but again do not offer any actual equipment for hands-on training. 73. Combination Training More recently, new modality training has been obtained through a combination of online pre-installation courses, followed by shorter sessions of hands-on equipment training. Eight hours of new modality training is required prior to independently performing digital breast tomosynthesis exams. As previously discussed, this new modality training can be provided by a super-user. Once the super-user has completed their training, they are qualified to train other technologists. It is important for the super-user to develop a training plan and keep detailed documentation of the training for inspection purposes Hour Requirement The DBT unit certification for each employee cannot be obtained until proof of eight hours of new modality training is submitted to the certifying body. Any educational certificates awarded for new modality training should be retained and readily available for current and future certification and accreditation purposes, and will be required during the facility s next annual inspection. 75. Radiologist Training Much like technologists, radiologists are also required to have eight hours of new modality training. This training can also be obtained through various means. The radiologist may have onsite applications training related to the display, review options, hanging protocols, and exam interpretation. A multi-day short course is another way a radiologist may obtain the training. Courses are generally offered at multiple locations and times. It can be hard to travel to these courses and finding a course prior to having the new modality installed also can be difficult. New modality training can be obtained through a combination of online pre-installation courses, followed by a shorter session of hands-on workstation training.

13 76. Medical Physicist Training Medical physicists who will perform the annual survey on the digital breast tomosynthesis units must complete eight hours of new modality training prior to performing any surveys. Again, this education can be acquired with onsite training, multi-day courses, or online courses. The medical physicist can acquire this training with other qualified medical physicists at other sites during other installations, or during the facility survey. Also, the medical physicist may acquire all or part of the training with the service engineer at the time the new equipment is installed. This can be done for both a complete tomosynthesis unit installation or for the addition of the tomosynthesis mode to existing 2D platforms. Additional online training prior to the installation can give the medical physicist the required eight hours. 77. Unique Feature Training Recently, the FDA has determined that each of the three approved DBT units possess unique features. For that reason, the FDA is now requiring additional training for all personnel on the unique features of a particular unit if the original eight hours of training were obtained on a different DBT unit. If you learn DBT on a Dimensions unit and change jobs to a facility that uses SenoClaire, you must have documented training by a qualified individual on the unique features of the SenoClaire. At present there are no set time requirements for the additional training, but documentation of training will be required at the annual inspection. 78. Radiologist Final Report The final interpretation of DBT studies is similar to those of digital mammography. The reporting requirements are the same. Generally, a sentence is added stating that images were acquired with tomosynthesis mode. The report should include the type of exam, screening or diagnostic, describe any abnormalities or other observations, establish a level of concern for malignancy, and provide recommendations for follow up. The report also should include a final assessment using the BIRADS categories. If the facility is located in a state with breast density regulations, the report might require an assessment of the patient s breast density. 79. Certification According to the FDA, facilities must first have certification and accreditation for FFDM components of a unit. The facility must then apply for that FFDM certification to include the tomosynthesis portion of the unit. For new installations, the process includes unit acceptance testing, personnel training and the completion of several forms, all of which must be done prior to performing exams on patients. For facilities that already have FFDM, the process only requires that the personnel training is completed and the forms are filled out. There are specific forms from the FDA that must be completed for DBT units. However, these are very similar to the FFDM forms and include items such as the manufacturer, DBT unit identification, image receptor identification, facility identification, review workstation monitor identification, phantom identification, personnel qualifications, manufacturer s quality control program and a completed Mammography Equipment Evaluation (MEE). For certification, a tomosynthesis phantom image in hard or soft copy format must be submitted to the FDA. 80. Accreditation There are currently no standards for accreditation in DBT. The modality is so new that these standards have not yet been developed. At this point, the images that are submitted for accreditation depend on the type of DBT equipment that a facility has available. If the unit uses 2D images and tomosynthesis, such as the Dimensions and Inspiration, the 2D FFDM images are submitted. If the unit generates a reconstructed 2D image from the tomosynthesis acquisition, as with the C-View or SenoClaire, the synthesized 2D images may be submitted. In either case the 2D portion of the unit must be accredited in order to perform digital breast tomosynthesis. 81. Knowledge Check 82. Knowledge Check 83. Conclusion

14 This concludes Breast Imaging Essentials: Module 10 Digital Breast Tomosynthesis. You should now be able to: Describe the digital breast tomosynthesis system. Explain the origin and theory behind tomosynthesis exams. Visualize the acquisition and display of DBT images. Discuss the benefits and challenges of this modality for both patients and staff. Define the similarities and differences of digital DBT and standard imaging. Differentiate current FDA approved units and their features. Recall QC tests and radiation dose specific to DBT. Explain the storage, distribution, and compatibility of DBT images. Recognize the training and certification requirements for DBT. 84. References Bushong S. Radiologic Science for Technologists: Physics, Biology, and Protection. 10 th ed. St. Louis, MO: Mosby; Levine G, Lopez J, Digital Breast Tomosynthesis. In: Francescatti D, Goer D, ed. Breast Cancer: A New Era in Management. New York, NY: Springer Science and Business Media; 2014: Kopans, DB. Digital Breast Tomosynthesis. GE Healthcare: Waukesha, WI; %20Digital%20Breast%20Tomo.pdf Average Glandular Dose in FDA-approved FFDM Systems. U.S. Food and Drug Administration Web site. EmittingProducts/MammographyQualityStandardsActandProgram/FacilityScorecard/ucm htm Updated January 1, Accessed October 24, Mammography Quality Standards Act National Statistics. U.S. Food and Drug Administration Web site. EmittingProducts/MammographyQualityStandardsActandProgram/FacilityCertificationandInspection/ucm htm Updated July 1, Accessed August 23, Baldwin P. Digital Breast Tomosynthesis. Radiol Technol. 2009; 81(1):57M-74M. Smith A. Fundamentals of Breast Tomosynthesis: Improving the Performance of Mammography. Hologic Inc: Bedford, MA; pdf Dobbins JT, Godfrey DJ. Digital X-ray Tomosynthesis: Current State of the Art and Clinical Potential. Phys Med Biol. IOP Publishing Ltd: 2003; 48(19): R