Research On Measuring Method Of X-ray Tube Voltage

X-rays are electromagnetic waves with very high frequency and very short wavelength.Since its discovery,with the development of science and research,it has been more and more widely used in all walks of life.In today’s society,there are more and more cancer patients,and breast cancer has been ranked the first among female patients and is still growing at the rate of 3% every year.Mammography is an important means of early examination,and the quality monitoring of examination equipment can ensure the image quality and the ability of early detection.For mammography X-rays machines,air kerma is the most important physical quantity that needs to be accurately measured and traced to the source.It is also very necessary to measure the tube voltage related to the penetration ability and image quality.Breast diagnostic radiation sources generally have two types of target,for less dense breast tissue is usually filtered by molybdenum target molybdenum,but for some thicker,denser tissue,higher energy is required to penetrate the general use of tungsten target rhodium filtration.The research on molybdenum target is relatively mature,but the research on tungsten target is still in the development stage.In this study,tungsten target rhodium filter reference materials with tube voltage of25 kV,28 kV,30 kV and 35 kV were established in the X-ray radiation field of breast industry of National Institue of Metrology,and the additional filtration materials were all0.05 mm Rh tablets.The half-value layer and effective energy are measured.The half-value layer of Al with a thickness of 0.48 to 0.57 mm has an effective energy between 17.3keV and 18.3keV,which is higher than the energy of the molybdenum target under the same tube voltage,it is easier to penetrate thicker tissues.The tube voltage of the optical machine was measured,and the switch optical machine,ripple,and background were analyzed by the interventional voltage division method.Finally,the average value can be used as the true value.The energy spectrum method is used to first calibrate the energy of the CdTe energy spectrometer through the radioactive source,and then collect the energy spectrum and use the end point method to take the tube voltage value,and verify with the voltage divider box.Then the same reference radiation quality is established in the medical breast radiation field,and the measurement of the dose and tube voltage is transferred through the transfer ionization chamber and the non-invasive detector.Finally,the uncertainty analysis is carried out,and the uncertainty of the air kerma is determined.The degree is0.45%,and the uncertainty of the tube voltage is 0.27%.