Applied Radiology

Kathleen M. Dallessio

More than 4 million mammograms will be performed in the United States this year, according to an article published in the June/July 2001 issue of Medtech Insight . The market for mammography equipment in this country, currently estimated at approximately $160 million, is expected to grow at a rate of 20% per year over the next 5 years, with sales expected to reach $340 million by 2005. Fueling this growth are several newly available technologies, full-field digital mammography (FFDM) and computer-aided detection (CAD). Also expected to contribute to this increase is optical imaging of the breast using computed tomography, technology that is not yet available in the United States.

Computed tomography laser mammography

Imaging Diagnostic Systems (Plantation, FL) appears to have the lead in the commercial development of CT laser mammography. In fact, the company recently received CE marking and an ISO 9002 approval to market their optical system, the Computed Tomography Laser Mammography (CTLM) system, in Europe. In the United States, the company has submitted all four modules for pre-market authorization (PMA) to the Food and Drug Administration (FDA) and has received approval for the first two modules. Clinical trials are currently under way at The University of Virginia and Nassau County Medical Center in New York.

In an interview with Applied Radiology , David Richter, MD, Medical Director at Imaging Diagnostic, explained how the CTLM works. "The CT Laser Mammography machine uses laser lights instead of x-ray, and, like any CT modality, it gives us the ability to make slices throughout the breast," he said. "The software then summarizes the data and gives us the ability to create a lateral view, a craniocaudal view, and a coronal view of the breast. It then can take all this information and make a 3D image of the breast, localizing exactly where the tumor is, if one is present."

The entire exam takes approximately 15 to 20 minutes, depending upon breast size, and is performed with the patient lying face down on a table and without compression of the breast tissue. The images are available within minutes, since the system processes one slice as the next is being obtained, Richter explained. The DICOM-compatible system also features CD-ROM image storage and a CD-ROM atlas of cases.

Richter cited several preliminary findings from the early trials. "For example," he noted, "what we are finding in cases of ductal carcinoma in situ is that: 1) the size of the tumor does not necessarily correspond with the size expected from the calcifications in the breast; and 2) in many cases, we can actually predict that the carcinoma in situ really has areas of invasive cancer in it" (figure 1).

He also noted that initial studies have shown that women with breast implants and those with dense breasts can be scanned better using the CTLM than with other modalities. "Since our findings are really based on increased vascularity and tumor angiogenesis, areas with implants obviously have no vessels in them, so they don't interfere with our scans," he explained. "The same thing seems to be true with the density of the breast; whether it is a dense breast or a fatty breast, the image is the same." He also noted that because there is no ionizing radiation involved, this scan can be repeated as often as necessary, which may be an important factor for patients who require repeated exams.

"At the moment, we are saying that we are an adjunct to mammography," said Richter. "This would be used much the same way as MRI and ultrasound are used right now in breast imaging."

The ongoing clinical trials focus on patients with Breast Imaging and Reporting Data Systems (BIRADS) classification in categories 3 and 4. "Quite frankly, there is no reason to do a test like ours, or any other adjunct test, in most BIRADS 5 cases," said Richter. "It is fairly obvious that those are going to be biopsied and additional studies don't really help." He said the goal at this point is for the CTLM system to identify the BIRADS 3 case that will turn out to be cancer, which may shorten the time to treatment.

Roughly 80% of BIRADS 4 cases are benign, and one of the goals of the system is to eliminate some of the BIRADS 4 cases that are biopsied. "We understand that it will take time before people have confidence in our machine and before they are willing to accept the results," Richter acknowledged, "but eventually that would be one of our goals."

Richter credited Imaging Diagnostic Systems' CEO Richard Grable with the creation of this system. Mr. Grable passed away on August 13 of this year. "This whole project was his dream. He truly dedicated the later years of his life to developing this. It's really one man's vision with the work of a lot of experts in every different field. He really was a remarkable man."

For a more in-depth look at this technology, see Grable R, Gkanatsios NA, Ponder SL. Optical mammography. Appl Radiol . 2000;29(2): 18-20, which is available at www.appliedradiology.com.

Full-field digital mammography

Another technology currently fueling the rapid growth in the mammography market is full-field digital mammography (FFDM). Two companies have recently unveiled plans to enter this growing arena.

Fisher Imaging (Denver, CO) recently announced that they had received an approvable letter from the FDA on its PMA application for the SenoScan digital mammography system. The company expects to receive final marketing approval in the coming weeks. Once approved, Fisher Imaging will join GE Medical Systems (Milwaukee, WI) as the only companies with FFDM systems available in the United States.

This new system, with a 22-X 30-cm field of view, generates a 25-micron pixel size in high-resolution mode, and a 50-micron size in standard-resolution mode. Its detective quantum efficiency (DQE) is 50% at zero spatial frequency, and it has a limiting resolution of 10 line pairs/mm at standard resolution, and 16 line pairs/mm at high resolution.

Further back in the developmental pipeline, Eastman Kodak Health Imaging (Rochester, NY) unveiled an amorphous selenium-based FFDM system as a work-in-progress at the 2001 American Healthcare Radiology Administrators (AHRA) meeting in Las Vegas, NV. The system is based on the same technology used in the company's line of digital radiography systems for general radiography, although a new source of amorphous selenium is used in the FFDM system. The company reports that the new material produces an 85-micron pixel pitch, and demonstrates significantly less noise in the amorphous selenium-based images when compared with similar images taken from amorphous silicon and charge-coupled device technologies.

The system, which will feature computer-aided detection (CAD) capabilities, is expected to include an x-ray generator, a digital detector, an operator console, a digital storage unit, and a DryView 8610 laser imager for printing images.

The system is currently undergoing prototype trials, with clinical trials slated to begin at three locations in late 2002. Kodak has not yet applied for a PMA.

Mammography reimbursement issues

Regulators recently recommended that reimbursement for mammographic exams should be increased to more accurately reflect the amount of work required to obtain these studies.

The Relative Value Update Committee (RUC) of The Centers for Medicare and Medicaid Services (CMS, formerly HCFA) has recommended an increase of 15% for bilateral exams and 18% for unilateral exams, according to reports published in the June 8, 2001 issue of the Federal Register . The RUC also recommended acceptance of changes in the current procedural terminology (CPT) codes as proposed by the American College of Radiology.

In other reimbursement news, a category 1 CPT code has been approved for the use of R2 Technology's ImageChecker CAD system (Los Altos, CA). The new code is considered an "add-on" because the product is used as a supplement to screening mammography.

Both of these changes are expected to be included in the American Medical Association's CPT 2002 codebook, scheduled for publication in November 2001.

Beekley introduces S-SPOT for marking scars

Beekley (Bristol, CT) recently introduced the Soft 'N Stretchy S-SPOT skin marker for localizing previous scar tissue during mammographic exams. The elasticity of the S-SPOT is designed to ensure that the marker stays in place while moving with the breast as it is manipulated during the exam.