Radiation-tolerant sensors help dentists visualize teeth
-andrew wilson
Formed in 1915, Welch Allyn Medical Products (Skaneateles Falls, NY) is best known as a maker of ophthalmoscopes, which can be found in nearly every doctor`s office. Now, the company is positioning its latest product, the Reveal Imaging Platform, as a tool to replace x-ray film in dentists` offices. According to Mike Stone of Welch Allyn, this dental platform can effectively reduce a patient`s radiation dose by as much as 90%, eliminate expensive and toxic-chemical-based procedures, and help visualize tooth structure during lengthy procedures such as root canals.
"At first," says Stone, "dentists resisted the purchase of such platforms because they were computer-based." According to Stone, dentists evaluated the networking of several computers in their offices as being too costly. In the design of the Reveal Imaging Platform, Welch Allyn developers teamed with InfiMed (Liverpool, NY) developers to build a stand-alone x-ray imaging system not based on computer technology.
The platform uses a 30 ¥ 23-mm imager to capture images that are digitized by a remote module and then displayed as S-video signals on a standard video monitor. To capture the x-ray image, the development team contracted with Cidtec (Liverpool, NY) to design a custom 800 ¥ 600 charge-injection-device (CID) imaging module.
"In ionizing radiation environments where instrumentation must be robust enough to resist radiation effects and provide real-time imaging capability, CID technology has distinct advantages over CCDs," says Andrew Beardslee, InfiMed manager of advanced product development. Based on 38.5-mm-square pixels, the imager provides the viewer with an equivalent 13-line pairs/mm resolution.
The development team also uses part of the sensor to trigger the analog video signal from the CID. After the video is streamed from the sensor, it is digitized by an 8-bit 20-MSPS TLC5510 analog-to-digital converter from Texas Instruments (Dallas, TX) and stored in the module`s 16 Mbits of DRAM.
After digitization, the video is encoded using a Bt121 encoder from Brooktree/Rockwell International (Costa Mesa, CA) as an S-VHS-compatible and two composite video signals that emerge from the digitizing module. The video signals are then displayed on a standard TV monitor.
"Rather than limit our customers to a computer-based system, we allow dentists to configure the system as they desire," says Welch Allyn`s Stone. "In most cases, dentists use the Reveal system as a stand-alone product. In others, PC-based image processors may be used as add-on peripherals to capture the image and perform further image analysis," he says.
