Bismuth Shielding in Head Computed Tomography-Still Necessary?

Area of Science:

• Radiological physics
• Medical imaging
• Radiation protection

Background:

• Cranial CT scans expose the radiosensitive eye lens to radiation, posing a greater risk to children.
• Current guidelines (IRCP 2021) discourage patient contact shielding in most areas.
• This study investigates the continued utility of bismuth shielding (BS) and its combination with other dose reduction technologies.

Purpose of the Study:

• To evaluate the effectiveness of bismuth shielding (BS) in reducing eye lens radiation dose during pediatric cranial CT.
• To assess the impact of combining BS with Automatic Exposure Control (AEC) and other dose reduction methods.
• To analyze the effect of BS and standoff foam on image quality in the orbital and cranial regions.

Main Methods:

• Pediatric anthropomorphic phantom used for cranial CT scans on two MDCT scanners.
• Eye lens doses measured using thermoluminescent dosimeters.
• Assessed image quality impact of BS, with and without standoff foam.

Main Results:

• BS significantly reduced eye lens dose on both scanners (GE: 41.50%, Siemens: 29.75%).
• Combination with AEC further lowered dose (GE: 60.75%, Siemens: 41.25%).
• Maximum dose reduction achieved with BS + AEC + OBTCM (GE: 71.25%, Siemens: 58.75%). BS increased orbital image noise, mitigated by foam; cranial image noise unaffected.

Conclusions:

• Bismuth shielding effectively reduces radiation dose to the eye lens in pediatric cranial CT.
• Combining BS with AEC and OBTCM significantly enhances dose reduction.
• While BS increases orbital noise, standoff foam mitigates this without affecting cranial image quality.