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This article is from the In-Depth Report Modernizing Medicine: Health Care in the Information Age

HDTV and Digital Cinema Chip Powers Medical Imaging Innovations

Digital light processing technology celebrates its 20th anniversary but its inventor has his eye on the future



Courtesy of Texas Instruments

Digital light processing (DLP), the technology behind high-definition television and digital cinema--as well as 3-D image rendering now under development that could lead to breakthroughs in medical diagnoses and treatment--turns 20 this month.

Introduced by Texas Instruments (TI) in 1987, DLP technology uses an optical semiconductor called a digital micromirror device (DMD) to digitally modulate light. A DMD does this using a rectangular array of microscopic mirrors that corresponds to light in a projected image. These mirrors tilt either toward or away from the light source several thousand times per second and can produce up to 1,024 shades of gray that can in some high-end projection displays be whipped into more than 35 trillion different colors.

Fans of the dazzling display of color and clarity made possible by DLP can thank TI fellow Larry Hornbeck for the series of innovations that transformed his work (exploring how the principles of reflection can be used to manipulate light) into today's high-definition entertainment, not to mention tomorrow's 3-D medical imaging systems. DLP technology ushered in "the age of digital enlightenment," says Hornbeck, 64, who at the end of the month will be inducted into the National Academy of Engineering in Washington, D.C., after more than three decades with TI.

In the late 1970s, TI assigned Hornbeck to work on a project for the National Security Agency (NSA) developing optical correlators able to swiftly detect objects, such as tanks and armored personnel carriers, during surveillance. The project paved the way for Hornbeck to develop DMD, which became the basis for DLP technology.

TI has shipped more than 12 million DLP units to date and the technology can be found in about 50 different HDTV models available from a number of different TV manufacturers. Also, more than 4,000 DLP Cinema projectors are in use, which accounts for 99 percent of the digital cinema installations in theaters worldwide, according to TI.

The introduction of DLP had a huge impact on the film industry, which until recently relied on expensive and bulky film reels to deliver movies to theaters. Feature film director and producer George Lucas was a fan of digital film and projection technologies from the start. In fact, the seminal moment for DLP Cinema projector technology came in 1999 when it was publicly demonstrated for the first time on two screens in Los Angeles and New York City marking the release of Lucasfilm's Star Wars: Episode I--The Phantom Menace. "I had tears in my eyes when the Star Wars film premiered," Hornbeck says. "I really, really got into the history of the technology of film. There was a historical sense of transition."

High-definition television and digital cinema just scratch the surface of DLP's capabilities. "Imagine a 3-D projector that targets an area of tissue where a tumor should be removed," Hornbeck says. Doctors are hoping that DLP technology will help them fix on tumors more accurately during radiation therapy to spare surrounding healthy tissue.

DLP technology is a key component of the Perspecta imaging system developed by Bedford, Mass.-based Actuality Systems to create 3-D renderings of patients' internal organs, including malignant and benign masses in them. To make these 3-D representations, thousands of two-dimensional images of cross-sections of each organ are projected at a rate of 5,000 images per second. The human eye cannot detect individual two-dimensional images at that speed, but instead sees an accumulation of them as one 3-D digital model. The end result looks like a hologram that provides medical professionals with a 360-degree digital rendering of the human body.

Not bad for a PhD from Case Western Reserve University in Cleveland with a doctorate in solid-state physics who had initially been turned down for a job by the very company where he would spend the next 34 years of his life. "I was resigned to drive a cab," he says about that first job interview in 1973. His career in the transportation industry never took off, however, because he was soon called back and offered a job helping Texas Instruments develop its emerging charge-coupled device (CCD) technology. "I told them I didn't know a lot about that," Hornbeck says, "and they told me I didn't have to, I already had the job. They figured correctly that based upon my PhD thesis research, I could bring things together and make them work."

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