Digital x-ray technology to help improve diagnostic image quality

Digital x-ray is changing the way the work of the Department of Radiology. This technology can reduce the radiation exposure of patients, improving diagnostic image quality, but also with conventional x-ray systems, can reduce the cost thousands of dollars in chemical processing.

Digital x-ray of forming can be divided into direct and indirect conversion.

Direct conversion of panel based selenium will not absorb a photon converts the charge directly, as shown in Figure 1. Indirect conversion using Flash materials will convert the optical photons, and then use photodiode, CCD or CMOS imaging sensor converts the light signal, as shown in Figure 2. Regardless of how the x-ray energy into electrical signals, you must convert from analog to digital signal for image processing. Although the entire image update rate is relatively low (15 ~ 120 frames/sec), probe it contains millions of pixels, while ensuring low-cost and low-power, high speed signals accurate conversion, and keep reading of high-precision is needed to respond to challenges.

Solution

Signal of direct and indirect conversion require ADC, its sampling rate should be equal to the array size and update rate of the product.

Cost-effective and power consumption minimum solution is the use of one or more high-speed ADC digitization of all pixels then. Large detector may need to use several ADC to desired update rate on digital images.

Although the standard image intensifier tube with 8 bit ~ 10 bit depth, the new probes have a wider dynamic range, use 14-bit, 16-bit even 18-bit of ADC.

With the improvement of dynamic range and sensitivity of these probes can generate free film higher quality diagnostic image, to bring more information. In addition to improving the diagnosis of the original data, digital processing can also increase the contrast, highlight differences in organizational density.

Analog devices offers a range of high speed, high resolution ADC to meet various detector array size and update rate requirements.

The highest signal-to-noise ratio, AD762116-bit PulSAR ADC-to-noise ratio (SNR) 90dB, conversion rate as high as $ 3MSPS. For a low dynamic range of the system, the SAR ADC in AD7484 14-bit 3MSPS sample rate of the signal to noise ratio (SNR) for 76.5dB. AD7621 and AD7484 is a successive approximation ADC, with excellent linearity, the image quality is an important parameter. For a high-speed ADC, AD9240 ADC chip with AD9244 14-bit respectively 10MSPS and 40MSPS/65MSPS sample rate. For the entire image requires a high update rate of the x-ray device, these line-ADC is ideal.