Effect Of Increase In Thickness Of Additional Al Filtration On X-ray Image Quality, Absorbed Dose Of Exposed Persons, And Risk Of Inducing Cancer

X-ray imaging diagnosis is one of the most essential methods employed in modern medicine. But the more radiological examinations and the longer duration in each examination one suffers from, the more radiation dose will be received by both the doctor and the patient. According to the linear no-threshold radiation risk model, the more radiation dose reaches the patient who is being underwent the radiological examination, the more probability of stochastic effect will be induced by it, that is to say the risk of inducing cancer, even the possibility of passing down the risk to the next generation is greater. In order to reduce stochastic effect, many efforts have being done to reduce the radiation dose of subject as much as possible in the proper use of radiation or under the guidance of the principle of rationalization, so that the total radiation energy imparted to the patient can be minimized as low as reasonably achievable (ALARA) degree.This paper investigated removing of the soft radiation quanta contained in the X-ray beam further by an Added aluminum filter with different thickness, monitored the X-ray image quality and the radiation dosage reaching the phantom surface under the filter with different thickness at the same time, and discussed the relationship between phantom surface dose and filter's thickness without affecting the image diagnostic accuracy under the ordinary X-ray apparatus and reasonable X-ray exposing technology used in clinical diagnosis. At last, in terms of a linear relative risk Poisson regression model, the reduction of the excess relative risk with the Added aluminum filter with different thickness was estimated.The results obtained show that in a certain range of thickness of the Added aluminum filters, the dose absorbed by patient surface is reduced drastically with the thickness of the Added filter increasing, but when the thickness of the Added aluminum filter's increased to a certain degree, the rate of reduction of patient surface dose will be slowed down with the thickness of filter increasing; X-ray tube's output load increases correspondingly with filter's thickness increasing, but image definition is less susceptible to increase of output X-ray intensity; in a certain range under consideration, as long as the dose of reaching image detector's input surface is certain, the impact on human vision due to beam hardening effect on image contrast and quantum-mottle is not obvious; and the estimated excess relative risk will be reduced obviously after the introduction of the Added aluminum filter.In this study, an approach of adding an Added aluminum filter to the X-ray beam is employed firstly to try to explore the probability of reducing the radiation dose reaching the patient's surface and the negative effect such as image degradation with the Added filter introducing, which can cause the increment of X-ray tube load and the beam hardening effect. Meanwhile, the reduction of the relative excess risk resulting from reducing per unit dosage was estimated after the introduction of the Added aluminum filter. The results are useful reference in protecting the patients who are being underwent the radiological examination from unnecessary radiation, and anticipated purpose of this paper is achieved.