Pediatric chest MDCT using tube current modulation: effect on radiation dose with breast shielding

Area of Science:

• Medical Imaging
• Radiological Physics
• Pediatric Radiology

Background:

• Pediatric chest CT requires careful radiation dose management.
• Bismuth breast shields and automatic tube current modulation (ATCM) are techniques to reduce radiation exposure.
• The interplay between shielding, ATCM, and image noise in pediatric CT needs further investigation.

Purpose of the Study:

• To evaluate the combined effect of bismuth breast shields and ATCM on radiation dose and image noise in pediatric chest 16-MDCT.
• To determine the optimal timing for scout image acquisition relative to shield placement for dose reduction.

Main Methods:

• An anthropomorphic phantom simulating a 5-year-old child underwent 16-MDCT chest scans.
• Scans were performed with and without a bismuth shield, and with ATCM, varying scout image timing.
• Radiation dose was measured at 20 organ locations using metal oxide semiconductor field effect transistor technology; effective dose was estimated via dose-length product; image noise was quantified using SD of Hounsfield units.

Main Results:

• A 2-ply bismuth shield reduced breast dose by 26%; combined with ATCM, breast dose reduction reached 52%.
• Placing the shield after scout imaging yielded the lowest organ doses and a 35% reduction in effective dose with ATCM.
• Image noise increased slightly (e.g., superior mediastinum: 11.4 to 13.1 HU) when the shield was placed post-scout but remained near the target noise index of 12.0 HU.

Conclusions:

• Placing the bismuth shield after scout imaging is crucial to prevent Auto mA overcompensation, maximizing radiation dose reduction.
• This technique effectively lowers radiation dose in pediatric chest CT while maintaining image noise within acceptable diagnostic levels.
• The combination of bismuth shielding and ATCM offers a promising strategy for dose optimization in pediatric CT examinations.