Developing Our First Fluoroscopic Amorphous Flat Panel Detector

Monday, March 5, 2018

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Rick Colbeth

Rick Colbeth

General Manager Vice President Flat Panel Detectors

When flat panel detectors for medical imaging were being developed in the mid-1990s, the detectors had about 10 times the noise and 100 times the minimum dose level of current detectors.  By 2001, the detectors had achieved the low dose requirements needed for medical fluoroscopy. Since 2001, the minimum dose levels have fallen by about a factor of four. Detector technology has come a long way and has overcome many barriers since 1990. Varex has also come a long way and we have been able to grow our product line to one of the broadest portfolios on the market.

Building the Prototype
In 1991, I worked with Michael Wright at the Varian Research Center in Tempe, Arizona, performing research and development (R&D) experiments on amorphous silicon flat panel detectors. At that time, we were one of the first to research the use of flat panel detectors for fluoroscopic and radioscopic digital imaging applications. We collaborated with researchers at the University of Michigan as well as Xerox Park, which provided us with amorphous arrays, or TFT (thin film transistor plates).

By 1993, we had built a full-size prototype detector for megavoltage (radiotherapy) applications. This prototype detector could also be used for kilovoltage (diagnostic) applications in radiography. On the basis of this prototype, we applied for the DARPA TRP (Defense Advanced Research Projects Agency Technology Reinvestment Project) contract through the US government. Out of a pool of 2,000 applicants, we were awarded a $6 million contract for three years (1994 - 1997). This funding eventually enabled us to create one of the first diagnostic flat panel detectors.

Varian Imaging Products (VIP)
In 1996, we formed VIP with the Varian Research Center and dpiX, a business venture with Xerox Park. The first shipment of VIP amorphous silicon flat panel detectors happened in 1997 and those detectors were for industrial imaging applications. Developing a detector that could be used for medical imaging applications was more challenging because we didn’t have the technology in place to create detectors that could deliver high resolution images with a low radiation dose for patients.

Developing the First Fluoroscopic Amorphous Silicon Flat Panel Detector
From 1998 until 2001, we worked to overcome technological barriers to develop a commercial amorphous silicon flat panel detector for medical imaging. The first steps involved forming a consortium with dpiX in 1998, which gave us access to TFTs and amorphous silicon arrays for flat panel detectors. Having our own source of arrays gave us a technological advantage that enabled us to develop a fluoroscopic panel for medical imaging.

In 2000, we moved VIP from Tempe, Arizona to a 5,000 square foot facility in Salt Lake City, Utah. We were essentially a start-up business of only a few people using space from an already existing X-ray tube factory. With the addition of a new tab bonding machine, and a larger facility, we were able to dramatically reduce the time it took to precisely place tabs from 6 hours to 15 minutes.

While beginning to automate was hugely important, the creation of a custom ASIC chip—called the Venus 4—was the key piece of technology that allowed us to develop a fluoroscopic amorphous silicon flat panel detector for medical imaging. Our customized chip enabled us to reduce the noise level for better resolution while keeping the radiation dose low.

In 2001, we developed our first prototype flat panel detector for fluoroscopic medical imaging: the PS4030. Because most of our competitors were working on developing radiographic detectors, we were one of the first in the world to offer fluoroscopic flat panel detectors, a unique technology. By 2004, we were shipping fluoroscopic panels to government and commercial customers throughout the globe.

Expansions and New Product Lines
By 2006 we had outgrown our facility. The Salt Lake City facility built an addition of 78,000 square feet. This addition included a brand new clean room, space for flat panel production, as well as an expansion of the shipping and receiving area servicing both panels and X-ray tubes. Another building update was a major redesign of the cleanroom layout completed in 2008, which expanded the soldering area and added an ultra-clean space for radiographic panel cleaning. 

These expansions enabled the development of radiographic flat panel detectors in 2008 and our custom product line of wireless flat panel detectors in 2009.

Transforming Dental Imaging
Further technological advancements were key to our growth in the dental flat panel detector industry. In 2010, dpiX opened a branch in Colorado Springs, Colorado, giving us access to more modern amorphous silicon.

Access to this advanced material—combined with higher capacity TAB bonders to attach ASIC chips to amorphous silicon arrays using glass manufacturing technology—enabled us to greatly increase our capacity and divide our fluoroscopy production into fluoroscopy and dental groups.

As a result, our advanced dental panel technology transformed the dental implant market. Our unique cone beam computed tomography (CT) software two-box tools allow clinicians to use a 2D detector to produce 3D volumetric-like CT Images.

Future Technological Growth
We are constantly looking for ways to enhance our products by using the latest materials like crystalline silicon and by adopting the latest technologies such as complementary metal–oxide–semiconductor (CMOS) technology. 

CMOS sensors have increased the resolution of our flat panel detectors while maintaining good low dose performance. With the acquisition of PerkinElmer Medical Imaging (PKI) in 2017, we now offer flat panel X-ray detectors with the CMOS sensor design to provide a new level of performance for mammography, fluoroscopy, cone beam CT, and radiography applications.