Organ-based tube current modulation and bismuth eye shielding in pediatric head computed tomography

Area of Science:

• Medical Imaging
• Radiological Physics
• Pediatric Radiology

Background:

• Ionizing radiation exposure to the eye lens can cause cataracts.
• Computed tomography (CT) utilizes several dose optimization techniques to mitigate lens exposure.

Purpose of the Study:

• To evaluate radiation dose to the eye lens, CTDIvol, and image quality in pediatric head CT.
• To compare automated tube current modulation (ATCM), automated tube voltage selection (ATVS), organ-based tube current modulation (OBTCM), and bismuth shielding for dose optimization.

Main Methods:

• An anthropomorphic phantom of a 5-year-old child was scanned using nine protocols, including combinations of dose optimization techniques.
• Eye, thyroid, and breast doses were measured using MOSFET dosimetry.
• CTDIvol, image noise, attenuation values, and subjective image quality were assessed.

Main Results:

• Bismuth shielding alone significantly reduced eye lens dose, comparable to software techniques alone.
• Combining bismuth shielding with software techniques reduced eye lens dose by up to 45% compared to no optimization.
• Bismuth shielding increased image noise, particularly in the anterior eye region.

Conclusions:

• A combination of ATCM, ATVS, OBTCM, and bismuth shielding (placed after localizer imaging) is recommended for reducing eye lens radiation dose in pediatric head CT.
• This comprehensive approach balances dose reduction with acceptable image quality.