Just as your TV is now high definition, so too mammography has shifted to digital technology and received a boost in resolution. Comparing methods of mammography, researchers from University Hospital Muenster, Germany, have discovered screening with a new photon-counting technique offers high performance while also enabling dose reduction. "The higher cancer detection resulting from the use of the [direct radiography] photon-counting scan system is due to high detection of both small, invasive cancers, and ductal carcinoma in situ," said Dr. Walter Heindel from the Department of Clinical Radiology at the University Hospital Muenster in Muenster, Germany. The results of his research appear online today in the journal Radiology.
Mammography is a specific type of imaging that uses a low-dose x-ray system to examine breasts. Such examination, called a mammogram, is used to aid in the early detection and diagnosis of breast diseases in women. Yet because radiation exposure is potentially dangerous, the goal is to use the lowest radiation dose possible while producing the best images to correctly evaluate the health of a woman’s breasts. Contemporary mammography systems have very controlled x-ray beams and dose control methods to minimize stray (also known as scatter) radiation. This helps protect the parts of a patient's body not being imaged and minimizes radiation exposure. "In population-based mammography screening, dose reducing techniques that don't compromise outcome parameters are desirable," Heindel explained in a press release.
To conduct the study, Heindel and his team of researchers analyzed data from the mammography screening program between the years 2009 and 2010 in the most populated German state, North Rhine-Westphalia. They compared the performance of a direct radiography (DR) photon-counting scan system with that of different screening units. With the general shift to digital technology, a range of computed radiography (CR) systems and DR mammography systems have emerged leaving radiologists to wonder how all the differences compare and contribute to accuracy. Both CR and DR can present an image within seconds of exposure. CR uses similar equipment to conventional radiography, yet it replaces film with an imaging plate (IP). Instead of taking an exposed film into a darkroom for developing, the imaging plate is run through a special scanner, or CR reader, that reads and digitizes the image — how does this influence the quality of the final image and a technician's ability to read it? By contrast, DR uses flat panel detectors, similar in principle to the image sensors used in digital photography in that they convert an optical image into an electronic signal. What impact does this have on image quality?
Ultimately, then, the team of researchers simply wanted to determine which system and technique produced the most accurate examination results at the lowest radiation dose.
The Clear Winner
For the study period, 13,312 women had been examined using the photon-counting system, while 993,822 women had been screened using either a CR system alone or a DR system alone. Where a higher rate is better, the researchers discovered the DR photon-counting scan system had a cancer detection rate of 0.76 percent for subsequent screening, compared to 0.59 percent discovered for the other screening units. In fact, the performance of the photon-counting technique was clearly superior to other methods; it had almost twice the detection rate of other methods for ductal carcinoma in situ (DCIS), an early, noninvasive form of disease. Most importantly, the mean average glandular radiation dose of the DR photon-counting scan system was significantly lower than the conventional DR systems.
"To our knowledge, the study is different from previous ones as we examined the performance of the DR photon-counting scan mammography on a larger database with consideration of multiple parameters of screening," explained co-author, Dr. Stefanie Weigel, from University Hospital Muenster.
Another screening factor the researchers have yet to examine is the new photon-counting technique allows for the modulation of lateral dose radiation — a helpful utility when scanning breasts of different density. (Cancer is more difficult to detect in women with dense breasts.) "One future research direction is the application of spectral imaging for quantification of breast glandular tissue, addressing the problem of breast density," Heindel said.
Source: Heindel W, Weigel S, Berkemeyer S, Girnus R, Sommer A, Lenzen H. Digital Mammography Screening with Photon-counting Technique: Can a High Diagnostic Performance Be Realized at Low Mean Glandular Dose? Radiology. 2014.