Medical Device Daily Contributing Writer

CHICAGO — The 96th Annual Meeting of the Radiological Society of North America (RSNA; Oakbrook, Illinois) was held here last week, with about 60,000 attendees from around the world, offering more than 4,000 scientific research presentations and education exhibits. Although the aisles in the exhibit hall were teeming with bodies, several exhibitors enjoyed more than their share of interest; among those were companies with functional imaging modalities for earlier detection or improved diagnostic capabilities for breast cancer. Functional imaging is complementary to mammography, providing a diagnostic tool that looks at cellular function as compared to the anatomical imaging of mammography and ultrasound.

Industry estimates that there are about 1.1 million breast biopsies performed worldwide annually; and when breast cancer is detected early, the remission rate at 5 years is 98%. Good odds, but what about those who do not get detected early or accurately defined at the time of diagnosis? With over 40 million screening mammograms projected in 2010, new advances in both early detection at screening, as well as improved imaging for diagnostic purposes were exhibited here at the RSNA. Functional imaging refers to the injection of a radiotracer that is absorbed differently by cancer cells than by healthy cells; or, in other words, is based on how the cells are functioning as opposed to how the cells appear. In addition to increased specificity that leads to improved diagnosis, functional imaging does not require breast compression like mammography does, so is better tolerated by patients.

A new tool to be used as an adjunct with screening mammography (when indicated) was showcased by GE Healthcare (Chalfont, UK). Contrast Enhanced Spectral Mammography (CESM) is a technology designed to allow a physician to image blood flow through angiography of the breast, allowing for a more definitive breast cancer diagnosis immediately following the screening mammogram. A contrast agent is injected to highlight angiogenesis, the growth of small blood vessels potentially related to the presence of cancer. In addition to typical mammography images that show breast tissue density, CESM technology is designed to provide doctors with images of contrast uptake, which may indicate angiogenesis (and possible cancer).

As mammography mainly images tissue densities, CESM has been designed to produce an image that maps contrast uptake, adding the functional information to the conventional standard tissue density information of mammography. Patients receive an intravenous injection of standard iodine contrast agent, and after two minutes undergo a five-minute digital mammography exam. CESM images are acquired in familiar mammography views so that they can be correlated with the original standard results, facilitating interpretation sooner.

Frequently, following their routine screening mammogram, patients are recalled for a diagnostic mammogram due to a suspicious area. These areas could be caused by a number of things, from simple technical errors, wrinkled breast tissue in the compression plate, movement, breathing, etc. Women who are recalled for a second mammogram often wait anywhere from 3 days to a month for their repeat mammogram, and are usually anxiety-ridden during this waiting time pondering the possibility that they may have breast cancer. With CESM, it is conceivable for patients who have suspicious areas on their screening mammograms to be recalled for a diagnostic mammogram before they even leave the office. They are given an injection of an iodinated contrast agent, and then have a second diagnostic mammogram using CESM. Results can be immediate, allowing the patient to continue with the next step of the process or go home relieved.

In a session on Emerging Technologies in Breast Imaging, Clarisse Dromain, MD, Department of Radiology, Institute Gustave-Roussey (Villejuif Cedex, France) presented “Contrast Enhanced Spectral Mammography: A Multi-reader Study.“ In this study that included a total of 150 proven lesions (86 malignant and 64 benign), clinical performance with CESM increased for each reader. Dromain concluded “The addition of CESM to standard mammography and ultrasound significantly increased clinical performance of clinical readers. CESM proved to be a valuable imaging technique as an adjunct to standard mammography and ultrasound for diagnostic patients.“ GE submitted the 510(k) for their CESM device last week, with hopes that the product could be on the market by the end of 2011. GE's strategy is to first offer a retrofit to each of the 3,700 existing GE mammography systems (representing approximately one-third of the total global market), for about $100,000 each. This exciting new technology may be able to provide a more definitive diagnosis on the spot for women whose screening mammograms are initially inconclusive.

Another aspect of improving breast cancer care is in the diagnostic phase of determining location, size, and extent of the disease both prior to and after surgery. Until recently, MRI has been the next tool employed after mammography and ultrasound; but although the sensitivity of MRI is very high, the specificity leaves room for improvement and also opens the door for other advanced imaging modalities to enter the market. Both positron emission mammography (PEM) and molecular, also called gamma imaging, have demonstrated similar sensitivity but improved specificity over MRI.

Privately held, venture-backed Naviscan (San Diego) was one of the five exhibitors selected to present their NIH-sponsored study to the press at the RSNA media center. This study is also published in Radiology 1:258 (2011) and revealed how their PEM technology may be able to reduce unnecessary biopsies due to its greater specificity. Wendie Berg, MD, PhD, principal investigator for the trial and a breast imaging practitioner at American Radiology Services-Johns Hopkins (Lutherville, MD) reported on the study of 388 women at 6 different centers demonstrating that PEM had a 6% improvement in specificity with comparable high sensitivity to that of MRI. In this study, Naviscan, the only breast PEM company, also showed 31 fewer unnecessary biopsies and 26 percent higher positive predictive value (PPV) than breast MRI. This finding is useful for the 15% to 20% of women who cannot tolerate an MRI or are ineligible for one because they have a pacemaker or other metal implant, are obese, or allergic to contrast agents and require an alternate imaging tool. At about half the cost of the average MRI system of $1.5 million, Naviscan doubled their revenues in 2010 and is currently doubling its distribution.

Another modality that increases the specificity with similar sensitivity to MRI is molecular imaging, also referred to as gamma imaging, scintigraphy, molecular breast imaging (MBI), or breast-specific-gamma imaging (BSGI). BSGI, or whatever you choose to call it, is a molecular breast imaging procedure that images the metabolic activity of breast lesions through radiotracer uptake. The Society of Nuclear Medicine (SNM) (Reston, Virginia) just published the procedure guideline for BSGI and CPT coding for diagnostic, pre-surgical and post-therapy use of BSGI is already in place. The first company in molecular imaging of the breast and market leader with 150 systems placed worldwide is privately held Dilon Diagnostics, a brand of Dilon Technologies (Newport News, Virginia). Dilon offers a high-resolution gamma camera that differentiates cancer cells by their increased rate of metabolic activity signified by a greater absorption of the radiotracer. The BSGI system is small, portable, office-friendly and also allows the patient to sit upright, unlike being prone in an MRI system. Dilon currently is the only advanced imaging company to offer an FDA cleared localization system as well as the ability to use all available biopsy devices, including those of Hologic (Bedford, Massachusetts) and Mammotome (Cincinnati) in conjunction with their imaging system. This means that not only can the physician see the lesion more definitively; they can also either mark the location (loc system) of the lesion for a biopsy later, or use a biopsy device under the gamma imager. Biopsy devices have been developed to work under X-ray guidance (stereotactic), ultrasound guidance, and MRI guidance. Now biopsies can also be performed using gamma-imaging guidance.

Gamma Medica (Northridge, California) also manufactures and sells a BSGI system with the option of either dual head or single head configuration. Single head is less expensive but takes a little longer to scan while dual head, though more costly, adds a stereotactic component and is quicker.