x ray unit settings: milliampere (mA)

This week will be covering the milliampere or mA setting on an x ray unit.  Changing the mA affects the QUANTITY of x rays produced.  Some units have a fixed mA (typically in the range of 7 – 12) and some are changeable (from 5 – 15).  For those units with a fixed mA, you will not be able to change this setting on your x ray unit.  😦

(Now onto the technical stuff)

Increasing the mA setting (ie, 10 to 15) increases the current in the low-voltage circuit.  This increase creates an increase in the temperature of the filament (cathode).  As the filament is heated it emits electrons.  The hotter it gets, the more electrons it emits.  These electrons are focused and move towards the target (anode) to create x rays.

(A quick note, that over 99% of the electrons that interact with the target will not produce x rays, but will give up their energy in the form of heat.)

The amount of x rays produced is proportional to the change in mA.  If you double the mA from 5 to 10, you will double the number of x rays produced.  I hope this short introduction to mA is educational.  Next week will be covering time and its affect on an x ray unit.  If you have any questions or comments about mA, please let me know.

Thanks and enjoy!


About Dr. Shawneen Gonzalez

Oral and Maxillofacial Radiologist having fun finding cool things on radiographs. :)

Posted on September 28, 2011, in Radiation Physics and tagged , , , . Bookmark the permalink. 1 Comment.

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