A decrease in the number of breast imaging specialists and facilities in the United States has led to concerns about patient access to proper care.1 The Government Accountability Office (GAO) observed declines in the total number of facilities (the FDA Web site2 indicates the loss of total facilities over the past several years) but suggested that both consolidation and maldistribution of resources were important factors in understanding potential access problems.3 The Institute of Medicine has predicted a shortage of both technologists and breast imaging specialists, indicating that, by 2015, the number of radiologists and technologists available to read 10,000 mammographic studies will decrease by 14% and 23%, respectively; the decrease predicted for 2025 is 23% for radiologists and 40% for technologists.4

Similar profiles are reflected in surveys of those contemplating a specialty in breast imaging. In a 2003 survey of radiology residents, 64% reported no interest in a breast imaging fellowship,5 and despite a national radiology fellowship match program for 2004, 75% of the breast/women’s imaging positions were unfilled.1 Beyond the fear of malpractice, the limited reimbursement schedules for breast imaging may impact such decisions. A survey of Society of Breast Imaging (SBI) members, subject to self-reporting bias, reported that 37% of all centers considered this field profitable, with 35% suggesting a negative economic impact on their practices.1 Ironically, physicians in other specialties have sought inroads into the field of breast imaging, especially interventional procedures, but to a lesser extent than the areas of neurological, musculoskeletal, and cardiac imaging.

Against this background, the field of breast imaging is undergoing substantial shifts in both technology and workflow. Perhaps this evolution will encourage interest in the field. A relative lack of interest by other specialties in this field offers an optimistic forecast for those in radiology prepared to embrace new developments.

Breast MR image captured with Vibrant Breast Imaging technology from GE Healthcare, Waukesha, Wis. Full-field digital mammogram captured with the Selenia from Hologic Inc, Bedford, Mass.
A breast ultrasound image captured with the z.one ultra system from ZONARE Medical Systems, Mountain View, Calif. Screen-film mammograms captured with Hologic’s Selenia.

Mammography: Digital Developments

The increasing awareness that properly performed screening mammography has a significant impact on mortality from breast cancer—combined with an almost deterministic trend toward digital imaging replacing analog imaging (consider how difficult it is now to find an analog photographic camera)—has encouraged both the development and acceptance of digital mammography. The requirements for FDA approval of full-field digital mammography (FFDM) were far more exacting than those for other fields, and the limited reimbursement schedules from government and private payors for digital technology that requires higher expenditures have restrained its introduction into the marketplace to some extent.

Following the publication of the American College of Radiology Imaging Network (ACRIN) Digital Mammographic Imaging Screening Trial (DMIST) results6—still subject to some controversy—and commensurate with other trends toward digital imaging, replacement of analog units by FFDM has accelerated. Current market prevalence approximates 15% to 20% with estimates for a possible 50% penetration of the market by the end of the decade. Although the trend might not maintain the current accelerated pace, conversion will undoubtedly continue. FFDM can be performed as CR, in which special imaging phosphor plates (IPs) replace current film-screen cassettes—requiring no replacement of current mammographic units—and are read by a laser excitation process in a dedicated image reader (IR). Both single- and multiplate image readers are available, depending on a balance of workflow goals and costs. FUJIFILM Medical Systems USA, Stamford, Conn, has received FDA approval for mammographic CR in the United States, and other applications are pending.

The alternative form of FFDM is direct radiography (DR), which uses several different approaches, all of which involve the replacement of the mammographic unit. Such techniques include both indirect and direct photon capture, employing either multitransistor arrays, or electronics tailored to direct photon capture by selenium plates. Several units have been approved by the FDA, with other applications pending. The advantages and disadvantages of all systems are beyond the scope of this discussion. In general, CR involves a smaller expenditure for equipment, especially when amortized over several units, but lacks the ability to incorporate several advanced platforms available to DR. CR, which involves the separate step of physically transferring exposed IPs to IRs (it takes approximately 1 minute per plate to read and return the IP for another exposure), requires a somewhat longer time to obtain and process images.

The introduction of FFDM affords the opportunity to readily interpret studies off-site, encouraging those most suitable to interpret breast imaging examinations regardless of physical location, as with any digital imaging that lends itself to teleradiology transfer. Permanent digital storage should obviate many problems related to lost films. However, the same technology that accomplishes these favorable outcomes is also the basis for substantial problems. Because of the proprietary development of so many different approaches to FFDM, the ability to annotate images, process them for presentation, store them in a PACS, retrieve them, and compare them to other studies from different vendors has been compromised by both connectivity and functionality issues. Some common requirements have been imposed beyond simple (and sometimes misleading) DICOM compatibility benchmarks; however, the current state of the art is counterproductive to the free flow of information.

In response, radiologists with expertise in breast imaging have played an unprecedented role in working with the vendor-based IHE initiatives for structuring future requirements over time that are intended to mitigate such problems. Comparing the size of an abnormality, for example, by importing a prior study from a different machine, can be difficult when the requirements for image display are not specific to how large the imported image must be. Although it is understandable that vendors may seek competitive advantages for their particular products, the future widespread adoption of FFDM will require such individual differences to be subordinated to common standards and parameters.

Mammography: Workflow Considerations

The dependence of the user on vendor-specified quality control measures (as approved by the FDA) and “for presentation” image display presents a new paradigm for interpretation. Overall market penetration is dependent on providing confident and satisfactory products; however, the user is far more limited in assessing developing problems. Consider, for example, an underpenetrated image, which, by analog standards, demonstrates insufficient exposure of the film (eg, too “white”). Such conditions are masked by image processing, which creates a “flatter” image with less contrast, an observation more difficult to recognize—especially when reviewing a large number of studies.

Workstations in mammography also suffer from a legacy in which the logistics were predicated on the presentation of CT and MR imaging, whereby static old and new studies are reviewed. For diagnostic work-ups, a dynamic approach is required whereby images are obtained often in a manner that is not prescribed. Although such workstations have been sold for nearly a decade, only recently have manufacturers begun to develop strategies to respond to this situation. (Remember that most sales and profits do not emerge from the mammography field for vendors with multiple line products.)

Indeed, workflow—rather than individual machine specification—is emerging as the issue of paramount concern for those in a digital environment. Although competitors may argue about preferences, all FDA-approved FFDM images are satisfactory. Servicing the number of examinations that will be required with an understaffed workforce will be impacted most by the ability to address workflow issues. If studies cannot be promptly and accurately “prefetched” from a PACS that lacks sufficient connectivity with workstations (at both the technologist and radiologist stations), workflow will be hampered.

It already has been observed that the interpretation times for screening FFDM are longer than for analog, with current increased reimbursement for FFDM (not a uniform practice) perhaps not accounting for such extra time. Diagnostic examinations require even more time under current conditions. Note in the discussion of CR and DR, workflow in terms of processing images will be shorter for DR, but this advantage does not entirely apply in a diagnostic or problem-solving environment where diagnosis, and not just satisfactory image production, is required prior to the patient’s departure. Institutions often see cost justification in more rapid throughput of screening patients afforded by FFDM, especially DR, but this in fact represents a cost shift to the radiologist, who must account for increased reading time with a premium reimbursement that might not be commensurate with resource allocation.

Finally, such advanced platforms as CAD and tomosynthesis are more suitable for FFDM. The efficacy of CAD has been demonstrated primarily for digitized analog images, with algorithms likely to be modified for direct digital capture. The Centers for Medicare and Medicaid Services (CMS), while mandated to reimburse CAD interpretations, has proposed a 50% decrease in such reimbursement over the next 5 years.8 Tomosynthesis is a technology suitable for DR and not CR. Current investigations of this technology as likely to increase sensitivity (finding soft tissue masses not seen on conventional images) and specificity (revealing summation artifacts) have been encouraging. Issues still to be resolved include achieving an acceptable dose for the likely two-view images (instead of the originally proposed one-view images) that may be required, as well as demonstrating calcifications distribution.

Ultrasound: Unit Improvements

The improved technology of ultrasound has afforded better image quality in both the development of higher-frequency transducers and image acquisition. Increased competition has contained rising costs for many units, making them more available for clinical use. Indeed, low-cost units have invited the interests of other clinical specialties where exacting requirements for image production and interpretation may not be as uniformly applied. For example, current efforts to “accredit” centers for breast ultrasound reflect considerable range in demonstrative skills and image quality.

The additional applications of tissue harmonics, in an organ system with such variable sound transmission, promised to improve diagnostic acumen. Most units employing this technique use pulse sequence applications, but some units also have provided differential harmonics being transmitted and received. Limited reports have not yet demonstrated improved outcomes. In like manner, spatial compounding should improve lesion edge evaluation, but limited studies (on older units) have not yet realized this potential.8 Finally, intravenous contrast administration of agents not yet approved for commercial use in the United States offers considerable promise for improving diagnostic accuracy. Such tools may become even more important as the issue of screening ultrasonography comes into public discussion. The ACRIN 6666 trial will soon report on its ultrasound screening results.9 The feasibility of both improved cancer detection and sonographic surveillance for lesions considered benign or probably benign will depend in part on achieving imaging parameters sufficiently reliable to avoid intervention, with proven outcomes similar to those established for mammography.

Finally, ultrasound remains the imaging modality of choice for image-guided biopsy and preoperative localization, primarily because of its ease of use, real-time needle placement usually associated with increased accuracy, and lower morbidity. In this context, it should be noted that CMS has proposed an 80% reduction in reimbursement over 5 years for the technical component of stereotactic biopsy.10 Sometimes, malignant calcifications can be seen with ultrasound (eg, within a mammographically occult mass), but most calcifications that undergo biopsy cannot. Thus, some cases that might have been subject to stereotactic biopsy may be approached more commonly with ultrasound. Whether this disincentive for stereotactic biopsy will cause the misapplication of ultrasound-guided biopsy cannot currently be determined.

MRI: Clinical Impact

The enthusiasm generated over the introduction of breast MRI using suitable coils and proper imaging techniques—not parameters that should be taken for granted, as evidenced by the wide variability of such approaches in clinical practice—has found acceptance in both the imaging and clinical communities. Evaluation of disease extent, more exacting assessment of response to the growing use of neoadjuvant therapy (both chemotherapy and hormonal therapy), identification of primary cancers already metastatic to axillary lymph nodes that cannot be felt or seen on mammography, and even screening for high-risk populations already have demonstrated considerable impact on clinical decision making and patient outcome. Indeed, recent FDA approval for the commercial release of silicone breast implants is conditional on MRI assessment of implant integrity over intervals of time.

Reimbursement for many indications of contrast-enhanced tumor studies by third-party payors has been slow and deliberate. In part, this caution has been in response to potential overuse of this expensive test. Problem solving accounts for many uses of MRI that could be seen as incentivized by higher reimbursement, especially in cases that have not been sufficiently evaluated by conventional means where a diagnosis could have been made more simply. In other circumstances, this indication may be more appropriately satisfied by MRI, but the range of applications by different facilities has introduced controversy.

The identification of suspicious lesions by MRI that cannot be seen by any other imaging modality has prompted the development of MR-compatible biopsy and preoperative localization devices, several of which are now promoted commercially. More commonly, if lesions are seen on MRI and an ultrasound correlate can be identified, tissue sampling is usually accomplished by ultrasound-guided biopsy. Sentinelle Medical Inc, Toronto, is conducting an investigation that co-registers ultrasound findings with positive MR findings in a manner such that otherwise nonspecific ultrasound findings may be subject to tissue sampling that previously would have required more time- and resource-intense MRI-guided biopsy.

Newer techniques, such as parallel imaging, are being applied to many organ systems, including the breast, with much optimism. Because current MR evaluation of breast lesions integrates both architectural or morphological appearances of a perfused abnormality, as well as the kinetics of that perfusion, the ability to populate k-space with more data points within a finite period of time should present the opportunity to obtain both higher resolution and more frequent data-point images that invite more accurate diagnosis. In addition, the possibility of finding safe contrast agents (perhaps with higher molecular weight than currently available gadolinium compounds that are used generically) will improve accuracy, especially if they can improve on the lack of specificity, which is a significant obstacle in breast MRI interpretation. Also, the development of new coil technology will exploit whatever current sequences are being employed to produce images of superior quality.

Finally, the application of spectroscopy has been shown to be feasible and effective for large lesions. However, most larger cancers display sufficient signs that diagnosis often is made correctly. It is the small lesions that appear on scans that escape confident imaging diagnosis, and in this area, spectroscopy has not demonstrated reliable application. Current focus on relative phosphocholine levels for 1T or 1.5T magnets is compromised by limited signal. Whether higher-strength magnets will demonstrate a regular and dependable role for spectroscopy, in order to avoid intervention that attends the growth of screening and other uses of breast MRI, awaits further analysis.

Next Steps: Better Practices

Current and new trends applicable to breast imaging involve efforts at new forms of imaging as well as better applications of current practices. New approaches being explored include dedicated breast CT units with 4-channel technology that is fundamentally different from the technology used during the 1980s to explore the use of CT in breast imaging. In a similar manner, better detectors for nuclear medicine agents have shown improved, if not convincing, results (eg, using Sestamibi). Given the emphasis on molecular breast imaging and the relatively well-studied mechanisms of fluorodeoxyglucose, both prototype and commercial breast PET units are being developed, sometimes exploiting the ability to co-register information from x-ray as well as nuclear imaging. In addition, ongoing investigations continue into physiologic measurements and imaging that may limit differential possibilities of lesions detected by other means. Such approaches often exploit other portions of the electromagnetic spectrum beyond x-ray and ultrasound, and include microwave imaging and near-infrared imaging where, through computer algorithms, various states of metabolic products may be determined.

Finally, reporting systems that track and assist in the reporting of results have invited a number of new companies to assist the radiologist or facility in applying the results of technology to clinical care.

Although a little knowledge might be a dangerous commodity, ignorance of the emerging technologies and applications in this field could be even more dangerous. Consider the state of the art in breast imaging 10 years ago compared to today, and it is difficult to escape the changes that have occurred. The rapidity of change over the next 10 years will require the practicing imager to be sensitive to the potential and limitations of evolving trends and technology, which may discourage clinicians in other specialties from engaging in this endeavor.

R. James Brenner, MD, is chief of breast imaging and professor of radiology at the University of California, San Francisco–Mt Zion Hospital Cancer Center, as well as a member of the Axis Imaging News Editorial Advisory Board. For more information, contact .


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