The use of a photoconductive detection scheme, in contrast to a scintillator light conversion approach, obviates the need for complex TFT arrays incorporating needed diode light detectors. This not only significantly reduces manufacturing costs, but also provides better resolution as a result of the elimination of blur due to the light spread. Mercuric Iodide’s excellent charge transport properties allow for very low voltages while maintaining high sensitivity, lowering the cost of electronics compared to other imagers, which work at many thousands of volts. 

Mercuric Iodide has been demonstrated to perform well at 30 frames per second in a fluoroscopic mode. With its good lag characteristics and its very high sensitivity, many consider it to be the best candidate for a flat panel replacement for image intensifier tubes, since Mercuric Iodide's sensitivity gives enough gain to overcome electronic amplifier line noise. 

 Advanced Readout Technology

Currently available readout circuitries are based on a 2-dimensional array of thin-film-transistor (TFT) switches, a technology used in active matrix flat panel displays. The thin-film technology enables very large imaging areas (up to 40 x 40 cm), and has a very high radiation tolerance. However, it has limitations in both resolution and performance (notably noise and contrast). These limitations are primarily due to the fact that TFT readout systems lack pixel amplification and that many pixels (entire lines, not individual pixels) are simultaneously addressed. These inefficiencies mean that the noise associated with the electronic signal (readout noise) is greater than the signal itself produced by the fluoroscopy exposure. The end result is degraded image quality, materially reducing clinical usefulness of the image examination to an unacceptable level. 

A further disadvantage of the TFT technology is that it requires a specialized fabrication process with a dedicated manufacturing facility, increasing both production and development costs relative to competing technologies.

RTR’s approach is to base the readout circuitry on CMOS (Complementary Metal Oxide Semiconductor) technology, the industry standard for electronic chips in computers and digital cameras. RTR believes that this technology will be less expensive and perform better than all available technologies. RTR’s CMOS circuitry approach takes advantage of the highly developed manufacturing infrastructure in the semiconductor industry by using the same fabrication processes used to make microprocessors and logic arrays. In other words, the integrated chip industry has already paid for the technology development and fabrication equipment and is continuing to invest in further improvements.

Today’s integrated chip processes allow the addition of special features on a per-pixel basis, vastly improving the performance of the image. The highly integrated architecture of CMOS based imagers allows the design of a “system on chip”, which is ultimately less costly than a TFT-based imager that requires a large amount of support electronics.