成人胸部适当高电压数字X线摄影试验研究

Optimisation of tube voltage for adult chest digital radiography

目的 探讨成人胸部不同厚度高千伏DR的适当电压千伏值.方法 用不同厚度的聚甲基丙烯酸甲酯（PMMA）模拟不同成人胸部厚度,用不同电压、自动曝光控制（AEC）摄影,记录入射体表剂量（ESD）、获取模体影像并计算影像质量因子（IQF）,绘制ESD和IQF之间的曲线.将一块厚度为1.8 cm（5 cm×5 cm）的PMMA作为对比物放在上述不同厚度PMMA上,用上述摄影方式和条件对其曝光,记录ESD,获取PMMA组合影像并计算信噪比（SNR）及影像质量因子倒数（IQFinv）.结果 不同胸厚的ESD均随着摄影电压的上升而下降,不同胸厚影像的IQFinv和SNR也都随着摄影电压的上升而下降.当摄影电压分别是70、100、140 kV时,胸厚为17.5 cm的ESD分别为0.22、0.09、0.06 mGy,IQF分别为43.3、58.8、72.0,SNR分别为7.5、6.2、5.0;胸厚为22.5 cm的ESD分别为0.37、0.12、0.06 mGy,IQF分别为56.0、61.4、65.3,SNR分别为6.4、5.2、3.8;胸厚为27.0 cm的ESD分别为0.52、0.20、0.09 mGy,IQF分别为54.2、64.3、91.0,SNR分别为6.0、4.8、3.5;胸厚为31.5 cm的ESD分别为0.53、0.24、0.10 mGy,IQF分别为53.2、66.8、95.3,SNR分别为5.7、4.5、3.0.结论 胸部数字高千伏X线摄影对于不同体质、胸厚的受检者不应使用一个固定千伏值进行摄影,应根据具体情况选择不同的千伏值.

Objective To explore the optimum voltage for digital chest radiography in adult. Methods PMMAs of Different thickness （7.2, 9.0, 10. 8 and 12. 6 cm） were used to simulate chest of different depth （ 17. 5, 22. 5, 27.0 and 32. 5 cm）. The combinants of contrast-detail Cdrad 2.0 phantom and above PMMAs were exposed with automatic exposure control （AEC） and different tube voltages. The images of these combinants were obtained and the entrance surface dose （ESD） was recorded. The imaging quality factor （IQF） was calculated and the curves were drawn between the ESD,IQF and kV. The PMMAs of different thickness, on which a contrast object （ PMAA of 5 cm diameter and 1.8 cm thickness ） was placed, were exposed with the same condition used for above test. Their images were obtained and SNRs were calculated. Results The ESD, SNR and IQFinv of different chest depth decreased with increase of kV.When tube voltages of 70, 100 and 140 kV were used, for 17. 5 cm chest depth, the ESD was 0. 22, 0. 09 and 0. 06 mGy, the IQF was 43.3, 58. 8 and 72. 0, the SNR was 7.5, 6. 2 and 5.0; for 22. 5 cm chest depth, the ESD was 0.37, 0.12 and 0.06 mGy, the IQF was 56. 0, 61.4 and 65.3, the SNR was 6. 4, 5.2 and 3. 8; for 27. 0 cm chest depth, the ESD was 0. 52, 0. 20 and 0. 09 mGy, the IQF was 54. 2, 64. 3 and 91. 0, the SNR was 6. 0, 4. 8 and 3. 5; for 31.5 cm chest depth, the ESD was 0.53, 0.24 and 0. 10 mGy,the IQF was 53.2, 66. 8 and 95.3, the SNR was 5. 7, 4. 5 and 3. 0. Conclusion To balance ESD, SNR and IQF, proper tube voltage should be chosen for chest radiography according to thickness and constitution of patients.