Lin Ming-Fang, Chen Chia-Yuen, Lee Yuan-Hao, Li Chia-Wei, Gerweck Leo E, Wang Hao, Chan Wing P
1 Department of Radiology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
2 Department of Medical Imaging and Radiological Technology, Yuanpei University, Hsinchu, Taiwan.
Acta Radiol. 2019 Jan;60(1):61-67. doi: 10.1177/0284185118770894. Epub 2018 Apr 17.
Multiple rounds of head computed tomography (CT) scans increase the risk of radiation-induced lens opacification.
To investigate the effects of CT eye shielding and topogram-based tube current modulation (TCM) on the radiation dose received by the lens and the image quality of nasal and periorbital imaging.
An anthropomorphic phantom was CT-scanned using either automatic tube current modulation or a fixed tube current. The lens radiation dose was estimated using cropped Gafchromic films irradiated with or without a shield over the orbit. Image quality, assessed using regions of interest drawn on the bilateral extraorbital areas and the nasal bone with a water-based marker, was evaluated using both a signal-to-noise ratio (SNR) and contrast-noise ratio (CNR). Two CT specialists independently assessed image artifacts using a three-point Likert scale.
The estimated radiation dose received by the lens was significantly lower when barium sulfate or bismuth-antimony shields were used in conjunction with a fixed tube current (22.0% and 35.6% reduction, respectively). Topogram-based TCM mitigated the beam hardening-associated artifacts of bismuth-antimony and barium sulfate shields. This increased the SNR by 21.6% in the extraorbital region and the CNR by 7.2% between the nasal bones and extraorbital regions. The combination of topogram-based TCM and barium sulfate or bismuth-antimony shields reduced lens doses by 12.2% and 27.2%, respectively.
Image artifacts induced by the bismuth-antimony shield at a fixed tube current for lenticular radioprotection were significantly reduced by topogram-based TCM, which increased the SNR of the anthropomorphic nasal bones and periorbital tissues.
多次头部计算机断层扫描（CT）会增加辐射诱发晶状体混浊的风险。
探讨CT眼部防护和基于定位像的管电流调制（TCM）对晶状体所接受辐射剂量以及鼻腔和眶周成像图像质量的影响。
使用自动管电流调制或固定管电流对人体模型进行CT扫描。通过在有或没有眼眶屏蔽的情况下照射裁剪后的辐射变色胶片来估算晶状体辐射剂量。使用水性标记在双侧眶外区域和鼻骨上绘制感兴趣区域来评估图像质量，并使用信噪比（SNR）和对比噪声比（CNR）进行评价。两名CT专家使用三点李克特量表独立评估图像伪影。
当硫酸钡或铋锑屏蔽与固定管电流联合使用时，估算的晶状体所接受辐射剂量显著降低（分别降低22.0%和35.6%）。基于定位像的TCM减轻了铋锑和硫酸钡屏蔽相关的束硬化伪影。这使得眶外区域的SNR提高了21.6%，鼻骨与眶外区域之间的CNR提高了7.2%。基于定位像的TCM与硫酸钡或铋锑屏蔽相结合，分别使晶状体剂量降低了12.2%和27.2%。
基于定位像的TCM显著减少了在固定管电流下用于晶状体辐射防护的铋锑屏蔽所诱发的图像伪影，提高了人体模型鼻骨和眶周组织的SNR。
