General Electric Company

Harold J Dalman

Russell Wayne Hum

Gerald K Flakas

Colin J Casey

Judith A Clifford

Phil E Pearson

A CT apparatus produces a trigger position signal having a programmable angular spacing, for triggering the acquisition of projections, from an encoder index pulse having a different fixed angular spacing. An estimation circuit estimates the time of occurrence of a next pulse in the trigger position signal by evaluating the timing of the encoder index pulses. The estimation circuit may be a phase-locked-loop or a set of lookup tables keyed to gantry position and speed.

Gantry position reference for tomographic scanners

The tube current in an X-ray tube is controlled by a closed loop control circuit in which a tube current feedback signal is used to control X-ray tube filament current. The gain of the feedback loop is maintained substantially constant over a wide range of tube currents by inserting a signal proportional to the reciprocal of the tube current command.

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Brookfield, WI, United States of America

Harold J Dalman