1. Fluoroscopic Brightness Control Systems
Based on:
Principles of Radiographic Imaging, 4th Ed.
By: R. Carlton & A. Adler
Radiologic Science for Technologists, 8th Ed.
By: S. Bushong
Syllabus on Fluoroscopy Radiation Protection, 6th Rev.
By: Radiologic Health Branch – Certification Unit
PPT created by: Jed Miles, BSRS, RT(R), CRT-CA

2. X-Ray Generators
X-ray generators used for static radiography are also used for fluoroscopy
Operator’s console has a control that will engage or activate the fluoroscopic system and bypass the static radiography system.

3. Brightness Control Systems
Wide variety of systems with different names are used to automatically maintain satisfactory fluoroscopic image density and contrast
Automatic Brightness Control (ABC)
Most common term
Automatic Density Control (ADC)
Automatic Brightness Stabilization (ABS)
All terms relate to and accomplish the same result:
Maintain brightness of viewable image
Automatically adjust exposure factors as necessary according to subject density and contrast

4. ABC Systems Monitor
Monitors electrical (electron) current flow between cathode and anode of image intensification tube
Or monitors light intensity of output screen
In all systems primary x-ray beam intensity is increased when the current and intensity fall below established levels

5. Regulation of Primary Beam
Regulation of primary beam accomplished by varying:
kVp mA
Pulse time
Most ABC’s will use a combination of these methods in a manner similar to stepped variable kVp systems
kVp is gradually increased to the maximum acceptable contrast level
Then mA is doubled while kVp is stepped down to the lowest acceptable contrast level
This process constantly repeated over and over

6. Response Time and AGC
Most ABC’s have a relatively slow response time, noticeable during routine fluoro
This is realized as a lag in the image brightness adjustment when rapid changes in tissue density are present
Example: Fluoro from lung field to abdomen
Automatic Gain Control (AGC)
AGC is part of the video camera control system
AGC will respond very quickly to change image brightness and density
Does NOT change x-ray exposure factors!

7. What’s Next?
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