X-ray detection chip is set to low cost of CT medical imaging

With the potential to make computed tomography (CT) scanners substantially more affordable, ams is introducing the S5950 integrated sensor chip for x-ray detection.

It combines a photosensor array and ADC in a single chip, reducing complexity and cost of sensor assembly in eight- and 16-slice CT scanners.

The AS5950 integrated sensor chip for X-ray detection will enable an improved CT detector for more detailed images at lower system costs, said ams, at the launch.

The AS5950 is a CMOS device that combines a high-sensitivity photodiode array and a 64-channel ADC on the same die. Being a single chip makes it easier to mount in a CT detector module. Current CT scanner manufacturers need to assemble a discrete photodiode array on a complex PCB, connected via long traces to a discrete read-out chip.

ams estimates that the medical imaging market for eight- and 16-slice CT scanners is expanding at a compound annual growth rate of 10 to 15 per cent.

The AS5950 has an optimum pixel size of 0.98 x 0.98mm². However, this can be customised upon request to suit the OEMs specific needs within a reasonably short lead-time.

The sensor can be directly assembled on a substrate using a wire bonding process for manufacturing of a CT module.

A CT module reference design simplifies the integration into a complete CT detector. This two-sided module has the sensors assembled on one substrate to build a sensor area of 32 x 16 mm² or 32 x 32 mm².

The AS5950’s integrated architecture features optimised wafer-level interconnects between the photodiode array and the read-out circuit to allow much lower noise than the board-level traces in a discrete photodiode/ADC assembly. This results in improved image quality. Noise in high-resolution mode is typically only 0.20 fC for a charge full-scale range of 455 pC. The ADC linearity of ±300ppm and the compound linearity of ±600ppm (including the photodiode) contribute to high image fidelity.

The low power dissipation of typically 0.65 mW per channel enables manufacturers to implement low-cost air cooling of CT scanners. An integrated temperature sensor enables monitoring of the junction temperature.

The AS5950 also offers fast integration time of as little as 200 microseconds to support high scanner rotation speed. The digital data readout can be accessed via SPI that also allows to configure active sensor area, pixel resolution and full scale range.

The AS5950 sensor IC as well as the AS5950M reference module are available for sampling now. An evaluation kit is also available to interface the sensor as well as the module reference design. It comes with a FPGA board and a software to demonstrate all relevant performance parameters.


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