Routine Daily Quality Control Multi Channel Analyzer (MCA) Energy Calibration

 

Center the clinically used Multi Channel Analyzer windows on the photopeak

  • Point sources of the clinically used radionuclides, of 37MBq (1mCi) activity each.

  • Stationary support for point source mounting

 

  1. With the collimator attached to the detector head, mount the source in the stationary support and align the head and the source.

  2. Select the collimator- source distance; the count rate detected should not exceed 30000 c/sec.

  3. Set the MCA at the energy of the radionuclide in use.

  4. Center the energy window on the nuclide photopeak.

  5. Record the calibration control settings.

  6. Remove the source and its support.

  • Record the MCA calibration settings. Plot these settings against date on a linear graph paper where reference and previous values have been plotted.

  • Compare the reference values and the ones of previous quality tests with the new data set. If deviation from previous set values is observed, the procedure should be repeated several times in succession and monitor fluctuations.

  • Short term fluctuation in data may arise due to unstable voltage or deviation on the temperature or malfunction of the electronic circuits. 

  • Long term trends of the calibration settings may be due to a malfunction of one or more photomultipliers, bad contact between the crystal and the photomultipliers or deterioration of the crystal. 

Deviations of the MCA settings greater than 10% must be checked and corrective action should be taken. 

 

Note:
• This test can be performed with the collimator removed; the activity of the point source used, then, should not exceed the 4MBq (100μCi).
•If the settings change only slowly, we may continue use the gamma camera but energy calibration of the MCA should be test before any study.

Routine Daily Quality Control
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