Automatic brightness control feedback and kV/mA curves
A schematic feedback loop: the x-ray tube sends a beam through the patient, whose attenuation varies with thickness; the image receptor forms an image and a brightness sensor samples the central region; the measured brightness is compared with a preset target and the tube output (kVp, mA and/or pulse width) is adjusted to hold displayed brightness constant. A small trend plot shows that as patient thickness or obliquity increases, tube output and patient dose rise while displayed brightness is held constant. ABC maintains brightness, not dose, and is not the same as AEC.
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