Sreeram Dhurjaty

The effect of finite gain in charge amplifiers in digital radiography

The effect of finite open-loop gain in charge amplifiers in digital radiography (DR) is analyzed. Practical charge amplifiers are usually integrated into silicon chips and commonly cater to 128 columns. High gains in charge amplifiers have a cost that is associated with greater chip count, greater power dissipation, and sometimes, reduced bandwidth. Even an open-loop gain of 1000 in a charge amplifier can lead to visible artifacts in a DR system, for temperature drifts of a fraction of a degree between calibration of a panel and subsequent usage, while acquiring a radiographic image. Furthermore, small gains in a charge amplifier can rob charge from the pixel capacitor and create residual charge, predominantly in the column capacitances. This can reduce the effective signal-to-noise ratios (SNRs). Analytical models are developed to illustrate the effects of the finite gain in charge amplifiers. Methods are suggested to decrease the deleterious effects of finite gains in charge amplifiers.

Foundations of Image Science

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Hard copy using thermal media and application to medical imaging

With the proliferation of various new modalities, in Medical Imaging, there has been a need for compatible hardcopy. In order to render color or colorized images, for diagnostic imaging, it is necessary to have high quality hardcopy. Thermal media has the necessary characteristics to display images emanating from most of the new medical imaging modalities. Furthermore, new image presentation techniques are enabling the display of some medical images, which could only be displayed using silver halide media.