摘要
目的 探讨数字化X线摄影（DR）焦点至探测器距离（FFD）与辐射剂量和影像质量的相关性。方法 去除滤线栅,采用自动曝光（AEC）模式对聚甲基丙烯酸甲酯和细节低对比度分析体模（CDRAD 2.0）进行DR摄影,管电压分别为70kV、90kV;通过手动调节,设定16个不同的FFD,在100-250cm范围内以10cm递增。记录曝光指数（EI）,采用X线剂量仪测量体表入射剂量（ESD）和管电流,计算影像质量因子倒数（IQF_（inv））,并进行统计学分析。结果 管电压70kV时,FFD与管电流呈高度正相关（r_1=0.993,P〈0.05）;FFD与EI呈中度正相关（r_2=0.649,P〈0.05）;FFD与ESD呈高度负相关（r_3=-0.935,P〈0.05）;FFD与IQF_（inv）呈中度度负相关（r_4=-0.699,P〈0.05）。管电压90kV时,FFD与管电流呈高度正相关（r_5=0.985,P〈0.05）;FFD与EI无相关性（r_6=-0.206,P〉0.05）;FFD与ESD呈高度负相关（r_7=-0.968,P〈0.05）;FFD与IQF_（inv）呈中度负相关（r_8=-0.628,P〈0.05）。r_1与r_5、r_3与r_7、r_4与r_8差异均无统计学意义（P均〉0.05）。结论 AEC模式下DR摄影,随着FFD自100~250cm范围内增加,可降低辐射剂量,但影像细节低对比度会略有降低,在实际应用中应根据诊断要求进行FFD参数的优化。
Objective To explore the ralationship of focus-to-flat panel detector distance （FFD） to radiation dosage and image quality in digital radiography （DR）. Methods Polymethylmethacrylate and CDRAD 2.0 phantoms were radio- graphed by DR auto exposure control （AEC） without filter grid under the 70 kV and 90 kV of tube voltage respectively. Sixteen different FFD （range 100-250 cm, 10 cm interval） were set. Exposure index （EI） was recorded, and entrance surface dose （ESD） and tube current were measured using X-ray dose measuring instrument. Image quality figure inverse （IQFinv） was calculated, and statistical analysis was carried out. Results When tube voltage was 70 kV, there were high positive correlation between FFD and tube current （r1 = 0. 993, P〈0.05）, moderate positive correlation （r2 =0. 649, P〈0.05） between FFD and EI, high negative correlation （r3=-0. 935, P（0.05） between FFD and ESD, moderate negative correlation （r4 =-0. 699, P〈0.05） between FFD and IQFinv When tube voltage was 90 kV, there were high positive cor- relation （rs=0. 985, P〈0.05） between FFD and tube current, high negative correlation （r7=-0. 968, P〈0.05） be- tween FFD and ESD, moderate negative correlation （r8=-0. 628, P〈0.05） between FFD and IQFinv. FFD and EI was no correlation （r6 =-0. 206, P〉0.05）. The differences between r1 and r2 , r3 and r7, r4 and r8 all had no statistically signifi- cant （all P〉0.05）. Conclusion When FFD is increased from 100 cm to 250 era, ESD of DR is reduced, but the detail con- trast of image is reduced slightly. The FFD must be adjusted according to clinical requirement.
出处
《中国医学影像技术》
CSCD
北大核心
2016年第8期1281-1284,共4页
Chinese Journal of Medical Imaging Technology
基金
甘肃省卫生行业科研计划资助项目(GSWSKY-2014-12)
关键词
放射摄影术
焦点至探测器距离
辐射剂量
影像质量
Radiography
Focus-to-flat panel detector distance
Radiation dosage
Image quality
