Brightness Control Systems

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

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) 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

Or monitors light intensity of output screen ABC Systems Monitor Monitor electrical (electron) current flow between cathode and anode of image intensification tube cathode Image Intensification Tube anode Or monitors light intensity of output screen Output Screen

ABC Systems Monitor In all systems, the “primary x-ray beam” intensity is increased or decreased when the intensified light output varies from established brightness levels Established Levels Current Intensity

Regulation of Primary Beam Regulation of primary beam is 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

Response Time Lung Field 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 Lung Field 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!

Please close this PowerPoint presentation, and continue the lesson. What’s Next? Please close this PowerPoint presentation, and continue the lesson. Presented by 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