Reduction in Lens Dose in Temporal Bone Computed Tomography by Modification of Scanning Plane
TF Lee, CY Chu, HT Sung, ST Leung, KW Leung, WK Kan
Hong Kong J Radiol 2016;19:91-5
DOI: 10.12809/hkjr1615339
Objectives: To evaluate the radiation dose reduction to the lens by modifying the scanning plane to exclude the orbit in temporal bone computed tomography (CT). The effect on diagnostic image quality was also evaluated.
Methods: Radiation dose reduction was evaluated using a phantom head and calibrated thermoluminescent dosimeters. Image quality was assessed in 34 patients. Two radiology fellows independently reviewed the image and assessed the image quality of 20 temporal bone structures. The image quality was scored on a 4-point scale and analysed with Mann Whitney U test.
Results: We demonstrated a 31.4% to 46.1% dose reduction to the lens by excluding the orbit in the scan field. The dose-length products before and after the modification were comparable (p = 0.267). None of the assessed temporal bone structures demonstrated any significant difference in image quality (p > 0.05).
Conclusion: Modification of the scanning plane in temporal bone CT can reduce radiation dose exposure to the lens and preserve the diagnostic image quality. This protocol should be considered to minimise the radiation exposure to patients.
中文摘要
進行顳骨電腦斷層掃描時改變掃描角度以減低眼晶體所接觸的輻射劑量
李騰飛、朱志揚、宋咸東、梁肇庭、梁錦榮、簡偉權
目的：進行顳骨電腦斷層掃描時改變掃描角度來剔除眼眶部分，以減低眼晶體接觸到的輻射劑量，並評估因此對圖像質量所造成的影響。
方法：使用假體的頭部和校準熱釋光劑量計來評估減少了的輻射劑量。測量了34個圖像的質量。兩名放射科醫生獨立審查各圖像，並評估20個顳骨結構圖像。利用4分制為圖像質量進行評分，並以Mann Whitney U檢驗進行分析。
結果：剔除眼眶範圍後發現眼球所接觸的輻射劑量減少了31.4%至46.1%。改變掃描角度前後的劑量–長度乘積沒有顯著差異（p=0.267）。顳骨結構的圖像質量並無任何顯著差異（p>0.05）。
結論：進行顳骨電腦斷層掃描時改變掃描角度可以減低眼晶體接觸的輻射劑量，同時可令圖像質量保存不變。應考慮這種做法來確保病人接觸輻射的劑量減至最少。