In a position statement, the American Association of Physicists in Medicine advise against using bismuth shields for dose reduction in CT scanning when alternatives are available.
Regular use of bismuth shields during CT scanning to protect anterior organs is not recommended by the American Association of Physicists in Medicine (AAPM) when alternatives for shielding are available.
Bismuth shielding has been traditionally used to shield radiosensitive organs such as the breast, lens of the eye and thyroid during CT scans.
“However, bismuth shielding degrades image quality, attenuates photons exiting the patient, and causes unpredictable results when combined with automatic exposure control systems,” the group said in a position statement released this week. Click here for a pdf of the full statement.
According to the AAPM, there are several known disadvantages to bismuth shield use, such as degrading image quality and accuracy, unpredictable and potentially undesirable levels of dose and image quality, and waste of some of the patient’s radiation exposure.
To avoid the use of the shield, suggestions include reducing the dose to the specific peripheral organs by adjusting automatic exposure controls (AEC) parameters and using organ-based tube current modulation techniques.