Gosch D, Gosch K, Kahn T
Klinik und Poliklinik für Diagnostische und Interventionelle Radiologie, Universitätsklinikum Leipzig AöR.
Rofo. 2007 Oct;179(10):1035-42. doi: 10.1055/s-2007-963237.
The effective dose, which is related to the stochastic radiation risk, cannot be measured directly. Therefore, conversion coefficients for estimating the effective dose for patients were calculated for fluoroscopy X-ray examinations from the dose area product which can be easily measured.
Conversion coefficients were calculated using the PC-based Monte Carlo program PCXMC in software version 1.5.1. Conversion coefficients were determined for tube voltages between 60 kV and 110 kV, for additional cupper filtration up to 0.9 mm, for different projections (a. p., p. a. and lateral) and X-ray field size (between 20 cm x 20 cm and 40 cm x 40 cm in image plane) and field position (from head to leg).
Tube voltage, filtration and field position have a significant effect on conversion coefficients. Conversion coefficients increase as the tube voltage and filtration increase. Depending on the radiation spectrum used, the conversion coefficients may differ up to a factor of 4 for the same X-ray examination. The highest conversion coefficients were found for irradiation of the body region followed by the head and leg region. The effect of the field size and projection is moderate. Conversion coefficients for a. p. projection are higher than those for p. a. and lateral projections.
Effective dose can be easily estimated by multiplying relevant conversion coefficients by the dose area product. Using conversion coefficients from the literature that do not take additional cupper filtration into consideration can underestimate the effective dose by a factor or up to 2 or more depending on the filtration used.
与随机辐射风险相关的有效剂量无法直接测量。因此，针对荧光透视X射线检查，根据易于测量的剂量面积乘积计算了用于估算患者有效剂量的转换系数。
使用软件版本1.5.1中基于PC的蒙特卡罗程序PCXMC计算转换系数。确定了管电压在60 kV至110 kV之间、附加铜滤过厚度达0.9 mm、不同投照方式（前后位、后前位和侧位）以及X射线野尺寸（影像平面中20 cm×20 cm至40 cm×40 cm之间）和野位置（从头到脚）时的转换系数。
管电压、滤过和野位置对转换系数有显著影响。转换系数随管电压和滤过的增加而增大。对于相同的X射线检查，根据所使用的辐射光谱不同，转换系数可能相差达4倍。身体部位照射的转换系数最高，其次是头部和腿部区域。野尺寸和投照方式的影响适中。前后位投照的转换系数高于后前位和侧位投照。
通过将相关转换系数与剂量面积乘积相乘，可轻松估算有效剂量。使用未考虑附加铜滤过的文献中的转换系数，可能会使有效剂量低估达2倍或更多，具体取决于所使用的滤过情况。
