1.0 Introduction; 1.1 Overview Of Abs Operation - CPI Indico 100 Series Service And Installation Manual

3E
ABS Calibration
3E.1.0 INTRODUCTION
3E.1.1 Overview of ABS Operation
Refer to figure 3E-1, this is a block diagram of the ABS system.
X-rays pass through the patient and excite the input cesium phosphor of the image intensifier
(I.I.). This will cause the output of the I.I. to fluoresce and project the image to the TV camera via the
collimating lens. A sample of the light output is then sensed by a photodiode or photomultiplier tube
(PMT), or composite or proportional video will be fed back from the camera.
The feedback signal is processed by the ABS circuits on the generator interface board. The result,
regardless of the type of ABS sensor used, will be a DC voltage proportional to the brightness of the
image. This DC signal is then processed by the generator CPU board. The CPU compares the feedback
voltage with a reference value determined by dose rate, mA, kVp, and mA ranges set during ABS
calibration. The CPU will attempt to maintain constant image brightness by varying the kVp and/or mA
output of the HF power supply according to a predetermined algorithm.
Page 3E-2
Figure 3E-1: ABS block diagram
Rev. D Millenia / Indico 100 Series Service Manual
CPI Canada Inc.
Ch # 740904-07