Main Factors Affecting Measurement Results of the Half-value Layer of Diagnostic X-ray Testing Equipment
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摘要: 为了保证诊断X射线设备应用的安全有效,针对三种型号的多参数测量仪,分析了测量过程中可能对半值层测量产生影响的诸多因素,比如X射线管电压、管电流、曝光时间、半值层仪的摆放位置等,设计多组对照试验。试验结果显示,管电压的偏差会导致半值层的改变,合适的曝光时间可以获得更加稳定的测量结果。Abstract: At present, there are many kinds of multi-parameter measuring instruments with the function of half-value layer(HVL) measurement in the market, which can be used to measure the HVL value of diagnostic X-ray equipment. Based on three types of multi-parameter measuring instrument, we analyze many factors that may affect the measurement of HVL, such as X-ray tube voltage, tube current, exposure time, and the placement of the HVL instrument, and then design several groups of control tests. The test results show that the deviation of the tube voltage leads to changes of the HVL and that more stable measurement results can be obtained with appropriate exposure time.
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Key words:
- half-value layer /
- diagnostic X-ray /
- tubevoltage /
- tubecurrent /
- exposure time
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表 1 常见型号半值层仪
Table 1. Types of half-value layer measuring instrument
仪器名称 型号 生产厂家 半值层测量范围和精度 X射线质量分析仪 RAYSAFE X2 FLUKE (1~14)mmAl,±10% MagicMaX IBA (1.3~10)mmAl,±10% Piranha-657 RTI (1.2~14)mmAl,±10% 表 2 诊断X射线标准辐射场半值层的参数
Table 2. NIM half-value layer parameters of diagnostic X-ray standard radiation
管电压/kV 附加过滤/mmAl 实测第一半值层/mmAl 50 1.226 1.777 70 1.619 2.581 80 1.619 3.010 100 1.981 3.969 120 2.392 4.995 表 3 管电压对半值层测量的影响
Table 3. Influence of the tube voltage
管电压/kV 实测半值层/mmAl 型号A 型号B 型号C 65 2.320 2.600 2.160 66 2.360 2.600 2.190 67 2.400 2.600 2.220 68 2.433 2.700 2.240 69 2.467 2.700 2.280 70 2.513 2.700 2.310 71 2.540 2.800 2.347 72 2.583 2.800 2.370 73 2.607 2.800 2.427 74 2.647 2.900 2.463 75 2.680 2.900 2.517 76 2.713 2.900 2.560 77 2.747 3.000 2.593 78 2.780 3.000 2.633 79 2.810 3.100 2.670 80 2.840 3.100 2.710 81 2.857 3.100 2.730 82 2.890 3.200 2.760 83 2.927 3.200 2.800 84 2.950 3.300 2.870 85 2.983 3.300 2.870 表 4 管电流对半值层测量的影响
Table 4. Influence of the tube current
管电流/mA 实测半值层/mmAl 型号A 型号B 型号C 63 2.508 2.700 2.330 80 2.510 2.700 2.320 100 2.512 2.700 2.310 125 2.510 2.700 2.330 160 2.509 2.700 2.310 表 5 曝光时间对半值层测量的影响
Table 5. The effect of exposure time
曝光时间/ms 实测半值层/mmAl 型号A 型号B 型号C 10 2.377 2.600 2.170 25 2.456 2.700 2.260 50 2.494 2.700 2.310 100 2.507 2.700 2.310 200 2.514 2.700 2.330 500 2.513 2.700 2.320 1000 2.514 2.700 2.330 表 6 探测器与焦斑距离对半值层测量的影响
Table 6. Influence of distance between the detector and the focal spot
距离/mm 实测半值层/mmAl 型号A 型号B 型号C 900 2.500 2.700 2.292 950 2.508 2.700 2.284 1000 2.508 2.700 2.303 1050 2.514 2.700 2.293 1100 2.520 2.700 2.283 表 7 夹角对半值层测量的影响
Table 7. The effect of the angle
偏离角度/° 实测半值层/mmAl 型号A 型号B 型号C 30 2.022 2.400 2.208 20 2.430 2.500 1.706 10 2.460 2.600 2.303 0 2.508 2.700 2.267 -10 2.481 2.700 1.537 -20 2.390 2.700 2.799 -30 2.322 2.600 2.208 -
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