A multichannel, high linearity current digitizer for digital subtraction angiography

An experiment studying the application of synchrotron radiation for transvenous coronary angiography requires special electronics to read out a 600-element Si(Li) detector. To obtain high image quality, the electronic system must digitize the current in all 600 elements every 2 ms with a dynamic range of 40000 and a maximum nonlinearity of 0.02%. Each channel of electronics contains a current-to-voltage amplifier with computer-controlled gain and offset followed by a voltage-to-frequency converter used in the reciprocal counting mode. A high-speed digital readout method using a lookup table, digital multiplier and direct memory interface was developed. The entire system has been designed to have a low cost per channel and to be easily expanded by 1200 signal channels.<
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