Dose reduction in CT by on-line tube current control: principles and validation on phantoms and cadavers
Dose reduction in CT by on-line tube current control: principles and validation on phantoms and cadavers
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DOI：
10.1007/s003300050674
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发表时间：
1999-01-01
影响因子：
5.9
通讯作者：
Bautz, WA
中科院分区：
文献类型：
--
作者：
Kalender, WA;Wolf, H;Bautz, WA
我们研究了在不损害图像质量的情况下减少CT剂量的方法。如果在患者X射线衰减较小的角管位置降低X射线管电流，则可以在不显著增加噪声的情况下减少非圆形对象横截面的剂量。我们通过模拟和体模测量研究了管子旋转过程中不同的电流调制方案。对预编程正弦调制函数和基于衰减的管电流在线控制进行了评估。所有相关的扫描参数都不同，包括最大调制幅度等约束条件。使用了一个圆形、一个椭圆形和两个椭圆形的水模。结果在6具身体上得到了验证。在不增加像素噪声值的情况下，对于不同的非圆形体模几何形状和电流调制算法，在模拟和测量中都获得了10-45%的剂量减少。基于衰减的在线控制比通过正弦曲线调制产生的减少更多。由于调制幅度的限制，模拟所预测的最大剂量减少无法实现。在身体研究中，身体通常减少了20%-40%，头部减少了大约10%。我们技术的变化是可能的；高衰减投影的正常管电流略有增加，结合基于衰减的电流调制，仍然可以显著减少剂量，但也减少了可能掩盖诊断细节的结构性噪声。我们的结论是，在不影响图像质量的情况下，通过管电流调制可以显著减少剂量。应采用基于衰减的在线控制和至少90%的调制幅度。
We investigated approaches to reducing the dose in CT without impairing image quality. Dose can be reduced for non-circular object cross-sections without a significant increase in noise if X-ray tube current is reduced at angular tube positions where the X-ray attenuation by the patients is small. We investigated different schemes of current modulation during tube rotation by simulation and phantom measurements. Both pre-programmed sinusoidal modulation functions and attenuation-based on-line control of the tube current were evaluated. All relevant scan parameters were varied, including constraints such as the maximum modulation amplitude. A circular, an elliptical and two oval water phantoms were used. Results were validated on six cadavers. Dose reduction of 10-45% was obtained both in simulations and in measurements for the different non-circular phantom geometries and current modulation algorithms without an increase increase in pixel noise values. On-line attenuation-based control yielded higher reductions than modulation by a sinusoidal curve. The maximal dose reduction predicted by simulations could not be achieved due to limits in the modulation amplitude. In cadaver studies, a reduction of typically 20-40 % was achieved for the body and about 10% for the head. Variations of our technique are possible; a slight increase in normal tube current for high-attenuation projections combined with attenuation-based current modulation still yields significant dose reduction, but also a reduction in the structured noise that may obscure diagnostic details. We conclude that a significant reduction in dose can be achieved by tube current modulation without compromising image quality. Attenuation-based on-line control and a modulation amplitude of at least 90 % should be employed.