Objective: To evaluate different protocol optimization strategies for temporal bone between10 μm otology CT and multi-slice CT (MSCT). Methods: Ten adult skull specimens (20-sides temporal bones) were prospectively enrolled. From October to November 2020, the temporal bones were scanned under four different imaging conditions using 10 μm otology CT (90 kV, 120 mAs; 90 kV, 140 mAs; 100 kV, 120 mAs; 100 kV, 140 mAs) and MSCT (120 kV, 220 mAs; 120 kV, 310 mAs; 140 kV, 160 mAs; 140 kV, 220 mAs), respectively. The image quality was subjectively scored using 5-grade scores, and the contrast noise ratio (CNR) of the image was measured. The absorbed dose of tissues and organs under different imaging conditions was measured by thermoluminescence dosimeter, and the effective dose was calculated. The figure of merit (FOM) is defined as the ratio of the square of the mean CNR to the effective dose. χ2 test was used to compare the difference of subjective scores of different scanning parameter groups, and paired t test was used to analyze and compare the difference of image CNR of different scanning parameter groups. The image quality, radiation dose and FOM of the combination of recommended parameters of the two devices were analyzed and compared. Results: For 10 μm otology CT, under 100 kV condition, the CNR of 140 mAs group was better than that of 120 mAs group (11.27±1.85 vs 10.26±1.38, P<0.001). There was no significant difference in subjective scores between the two groups [5.00 (4.00, 5.00) vs 5.00 (4.25, 5.00), P=0.264]. For MSCT, under 120 kV condition, the subjective scores and CNR of 310 mAs group were better than those of 220 mAs at 120 kV [4.00(3.00, 4.00) vs 3.00(3.00, 3.00),P=0.002;5.24±0.62 vs 4.60±0.62,P<0.001]. According to the principle of image quality-radiation dose optimization, the combination of 100 kV with 120 mAs and 120 kV with 310 mAs are recommended for 10 μm otology CT and MSCT, respectively. The subjective scores and CNR of 10 μm otology CT images were better than those of MSCT (5.00 (4.25, 5.00) vs 4.00 (3.00, 4.00), 10.26±1.38 vs 5.48±0.22, P<0.001). The effective dose was 1/3 of that of MSCT (82.99 μSv vs 252.56 μSv), and the FOM was 11.16 times of that of MSCT (1 268.44 mSv-1 vs 113.71 mSv-1). Conclusion: The temporal bone image quality of newly developed 10 μm otology CT is significantly better than that of MSCT, and its effective dose is lower than that of MSCT, which has more accurate and safer application potential.
目的： 探讨10 μm级耳科专用CT与多层螺旋CT（MSCT）颞骨成像方案优化的试验对比情况。 方法： 前瞻性收集10个成人头颅标本（20侧颞骨），于2020年10至11月分别采用4组不同成像条件进行10 μm级耳科专用CT（90 kV、120 mAs；90 kV、140 mAs；100 kV、120 mAs；100 kV、140 mAs）和MSCT（120 kV、220 mAs；120 kV、310 mAs；140 kV、160 mAs；140 kV、220 mAs）扫描。应用5等级评分对图像质量进行主观评分并测量图像的对比噪声比（CNR）。应用热释光剂量片测量不同成像条件下的组织器官吸收剂量，并计算有效剂量。定义质量因数（FOM）为CNR均值的平方与有效剂量的比值。采用χ²检验分析比较不同扫描参数组的主观评分差异，采用配对t检验分析比较不同扫描参数组图像CNR的差异。分析比较两种设备推荐参数组合的图像质量、辐射剂量及FOM。 结果： 对于10 μm级耳科专用CT，100 kV条件下，140 mAs组图像CNR优于120 mAs组（11.27±1.85比10.26±1.38，P<0.001），两组图像主观评分的差异无统计学意义［5.00（4.00，5.00）比5.00（4.25，5.00），P=0.264］。对于MSCT，120 kV条件下，310 mAs组主观评分及CNR均优于220 mAs［4.00（3.00，4.00）比3.00（3.00，3.00），P=0.002；5.24±0.62比4.60±0.62，P<0.001］。根据图像质量-辐射剂量最优化原则，10 μm级耳科专用CT和MSCT的成像参数组合分别推荐100 kV、120 mAs和120 kV、310 mAs。10 μm级耳科专用CT图像主观评分和CNR均优于MSCT［5.00（4.25，5.00）比4.00（3.00，4.00），10.26±1.38比5.48±0.22，P<0.001］，有效剂量是MSCT的1/3（82.99 μSv比252.56 μSv），FOM是MSCT的11.16倍（1 268.44 mSv-1比113.71 mSv-1）。 结论： 新研制的10 μm级耳科专用CT的颞骨图像质量显著优于MSCT，有效剂量低于MSCT，具有更精准、更安全的应用潜力。.