| Objective:Chest X-ray examination of the infant has its irreplaceable advantages, because it has a low radiation dose and convenient advantages. In addition, children physical development particularity, the probability of the cells in mitotic phase was higher than that of adults, and mitotic cells under X-ray radiation causes mutation probability is much higher than that of non dividing cells, the sensitivity of X-ray of the children more than 10 times that of adults. In addition, because the specificity of child body of the organizational structure, the human body to X-ray absorption is greater than for adults, probably per milliampere second radiation dose of 1.6 ~ 1.7 times higher than that of adults. The average survival time in infants is much higher than that of adults. infants if you don’t pay much attention to control of radiation dose of X-ray radiation, the survival period accepted will be much higher than adults. Low measurement therefore study of infantile photographic projection is very necessary. The purpose of the experiment is to study the infant DR high voltage chest radiography in the diagnosis of the premise of meeting the need, its produce the minimum radiation dose exposure condition for. Methods : The machine for Japan’s SHIMADZU RAD producing SPEEDM high frequency digital photography X-ray machine, new medical technology(Shanghai) Co., Ltd. SATURN8000 series image workstation is linked to the SONY company High Resolution UP-DF750 dry laser printer. Phantom by Shanghai Zi source trading company sales of American FLUKE the product model for 76-414-4150. Detector for radiation dose for Radiation Protection Technology Co., Ltd. Shenzhen he BH-3013 B portable radiation dose detector and definition test card. The phantom in accordance with the normal projection position is placed into the X machine, the projection distance is 100 cm, the aperture size for phantom quite. The phantom in the tube voltage of 60 k V, 70 kv, 80 k V, 90 KV and 100 k V respectively 30 exposures, tube power flow m As(milliampere second, m As) with automatic following exposure. Every time the appropriate adjustment of the phantom thickness to simulate different babies. Records of each investment and radiation dose area as phantom value(dose area product DAP d Gy. c ㎡). To evaluate the image quality obtained by 3 technicians with rich experience in the diagnosis of the deputy director and above physicians and 2 deputy director and above titles. With the single blind method was clear, general and poor three evaluations according to the image quality evaluation standard of the State Council issued health planning commission. The experimental data were processed by SPSS17.0 statistical software, the radiation dose area values were analyzed by t test. Evaluation of image quality using the chi square test, different comparison clear set of images and fair and poor groups of images, inspection standard for a=0.05. Results:Experimental results show that the 60 k V when the average m As is 3.96, the average radiation dose area value is 1.24, the image was clear in 26 cases, 4 cases of image. 70 k V when the average m As is 3.75, the average radiation dose area value is 1.05, the image was clear in 28 cases, 2 cases of image. 80 k V when the average m As is 3.52, the average radiation dose area value was 0.86, in which the image was clear in 27 cases, 2 cases of image, image difference in 1 cases. 90 k V when the average m As is 3.31, the average radiation dose area value is 0.67, the image was clear in 28 cases, 2 cases of image. 100 k V when the average m As is 3.25, the average radiation dose area value was 0.64, in which the image was clear in 12 cases, 8 cases of image, image difference in 10 cases. With the increase of KV, the average radiation dose of phantom surface area values decreased gradually, with the linear correlation analysis showed that with increasing the tube voltage, surface radiation dose reduction, the correlation coefficient is r=-0.705, P=0.000; image quality by by chi square test was statistically significant(= 40.353, P=0.000), after two two chi square inspection, 60 k V, 70 kv, 80 k V,90KV and 100 k V(2c=14.067, P=0.000, 2c=19.200, P=0.000, =16.484, P=0.000, 2c=19.200, P=0.000,) was statistically significant, between 60 k V, 70 kv, 80 k V, 90 KV two two were statistically(2c=0.19, P=0.005, 2c=0.00, P=0.005, 2c=0.00, P>0.005). From the above m As value can see another advantage of high voltage photography is that shortening the pipe flow of power, which means that shorten the exposure time(tube electric flow = tube current * exposure time), it is very important for infants and young children photography, because the infant’s compliance is poor, can not conduct the breath holding projection, even a lot of infants projection of agony, these are serious impact on image quality, shorten the time after exposure can influence on image quality to reduce these factors to a great extent, so as to meet the demand for diagnosis. Thus it can be considered a high voltage is effective in reducing infant chest photography cast method for radiation dose according to process, which shorten the exposure time, method for reducing motion artifacts is also suitable for the infant’s chest radiography, can reduce infant because artifacts because of poor compliance and can’t breath generated. Conclusion:Through this research we found that, with the improvement of voltage, milliamperemeter decreased gradually, the radiation dose area phantom value has been gradually reduced, 60-90 kv image quality was not statistically significant. But the radiation dose area was gradually decreased, but 100 k V image quality will be decreased, compared with the previous 4 sets of images have significant difference. Its image quality is obvio. Its image quality is obviously not as good as the former. Therefore, the high voltage photography under 90 KV is to minimize the radiation to meet the needs of diagnosis. So this method is worthy of popularization and application of photography... |
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