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The effect of x-ray tube voltage on the initial surface dose.
HYKA, Daniel
Relating to the adoption of the Law No.18/1997 of the Legal Code, the so called ?Atom Law? amended with the Law No. 13/2002 of the Legal Code, the radiation protection regulations were considerably toughen. According to the Paragraph 4 of the Law each subject executing operations resulting in radiation is obliged to ensure priority radiation protection. In addition, each subject is obliged to implement quality assurance system according to the Regulation No.214/1997 of the Legal Code and each subject authorized to handling sources of ionizing radiation is according to the Paragraph 18, Article I, Letter a) of the Atom Law also obliged to monitor the source of ionizing radiation by monitoring, measuring, evaluating and recording relevant figures. The Law No. 18/97 of the Legal Code also imposes the obligation to maintain such level of radiation protection that the life and health hazard and the environmental threats are as low as it is reasonably possible when economic and social views are taken into account. This optimization is attained with the implementation of the quality assurance program, which contains the long-term stability test. One of the steps leading to optimization and reduction of the ionizing radiation dose is correct selection of the load parameters of the X-ray machine. An important factor is the used voltage of the x-ray tube; it affects the input surface kerma, which is the fundamental information for the subsequent estimation of the effective dose. Changing this parameter can considerably effect, or decrease, the absorbed dose for the patients and the staff. Often such conditions arise which necessitate a voltage change, which on the other hand require a change in exposition (mAs or distance). However, we have to keep in mind that increased voltage together with adjusted exposition with the average density maintained the same; will result in lower image contrast, because the x-ray radiation produced with higher voltage reduces the subject contrast. The same applies vice versa, i.e. when voltage is decreased, subject contrast is increased. The objectives of the practical part of the thesis is to find out based on dosimetry measurement using a phantom, what is the effect of the voltage change on the x-ray tube on the increase or decrease of the radiation load on patients during skiagraphic procedures.
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