Radiation-Emitting Products

Technique Factor Selection and Display

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900.12(b)(9)(i),(ii),(iii): Technique factor selection and display.

(i) Manual selection of milliampere seconds (mAs) or at least one of its component parts (milliampere (mA) and/or time) shall be available.

(ii) The technique factors (peak tube potential in kilovolt (kV) and either tube current in mA and exposure time in seconds or the product of tube current and exposure time in mAs) to be used during an exposure shall be indicated before the exposure begins, except when automatic exposure controls (AEC) are used, in which case the technique factors that are set prior to the exposure shall be indicated.

(iii) Following the AEC mode use, the system shall indicate the actual kilovoltage peak (kVp) and mAs used during the exposure. The mAs may be displayed as mA and time.


  1. Would an x-ray unit with both a manual mode and an automatic exposure control mode assure that the mAs selection requirement is met?
  2. When used in manual mode a facility's x-ray unit displays kVp, mA, and time before the exposure. When in AEC mode, the display usually changes from the preset indications after the exposure. Does this meet the requirement?
  3. Are there any specific requirements for the mechanism of the display required by 900.12(b)(9)(iii)?
  4. If only the preset kVp is displayed by the unit when used in the AEC mode, is it necessary for a "preset" indication of mA and/or mAs to be indicated prior to the exposure?


Page Last Updated: 08/11/2014
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