Routine Daily Quality Control Background Count rate Check

 

Check the background count rate of a gamma camera system, under conditions of clinical imaging by a particular radionuclide

  1. Mount the collimator to be used and turn the detector head to a scanning position downward.

  2. Position the detector head over the center of the table bed.

  3. Adjust all the routine settings on the gamma camera console, for a routine acquisition by the radionuclide concerned.

  4. Perform a count measurement for a 100sec recording time without any radiation source at the vicinity of the camera.

  5. Record the counts and calculate the background count rate.

  • Compare the calculated value of the background count rate with the reference one and background recent values to identify any changes or trends.

  • A rapid increase of the background count rate may be due to a contamination of the camera system -particularly on the collimator face-, the floor, and the bed or to the presence of radioactive sources near the camera.

  • If none of the above is present, the background may be due to electronic "noise".

  • An increase of the background count rate above the 20% of the reference value should lead to further investigation.

  • Record whether the measurements confirm acceptable performance; if not, corrective action should be taken.   

 
Note:
• Patients to whom radiopharmaceuticals have been administered, radioactive wastes in the camera room or even contamination of the person carrying out the test may be a "background radioactive source" 
• An increased background rate that persists in a monitoring over a period of days, an electrical fault of the system may be suspected.

Routine Daily Quality Control
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