Santa Clara, CA —The GE Senographe®2000D is the first digital mammography system approved by the FDA in the U.S. A large-format x-ray detector from Perkin Elmer Corp. enables it to challenge traditional photographic film-based mammography systems.
"Of the 32.5 million mammograms performed annually in the US, current technology misses some 15,000 to 45,000 cases," says Dr. Karina Bukhanov, head of Division of Breast Imaging at Princess Margaret Hospital in Toronto. "The capabilities of this new digital system carries the promise of saving lives by improving early diagnosis of breast cancer."
Previous attempts at digital imaging for diagnostic x-ray included charged-coupled devices (CCDs) which compromised imaging performance because the detectors were small, measuring only a few inches on a side. Capturing a full chest x-ray image meant passing the x-rays through a "reduction screen" before they struck the small-scale detectors. Such images have little value to the medical community, according to Fred Pla, an engineer at GE Medical Systems.
Conversely, the Perkin Elmer detector panel has a large format and high-pixel density that eliminates the need for optical image reduction. The large-scale detectors have a glass-panel substrate with layers of silicon, metals, and insulators applied using the same photolithography techniques that create photodiodes. A scintillator material converts the x-ray photons to visible light. With techniques similar to those used for liquid-crystal-display manufacturing, the completed x-ray detector is connected to integrated circuit amplifiers and electronics needed for building a pixel-by-pixel x-ray image. "It's similar to a flat panel display, but it has a much higher resolution," says Pla.
Doctors and technicians can review images faster with digital mammography because the images are processed within 10 seconds of an exposure, providing the technologist with quick verification of correct patient positioning and often preventing the need for repeat exams. Total time for the average exam is less than 15 minutes versus the 30 minutes for a typical film mammography exam.
Digital mammography also lets doctors do more with the images than film-based systems. Doctors examine, magnify, and manipulate images. Digital images also provide better visibility of the breast, particularly near the skin line, because they have a greater number of gradients between lightest and darkest regions on an image. Thus, the person viewing the images discerns finer variations in tissue density, thereby improving diagnoses.
In addition, electronic storage of x-ray images is expected to save hospitals enormous space and labor costs devoted to archiving and retrieving x-ray film. Digital storage dovetails well with computerized maintenance of patient records, allowing x-rays to be electronically collated with patient histories and test results.
Digital x-rays have applications beyond medicine, including non-destructive testing of components such as aircraft turbine engine blades.