When preforming quality control tests everything must be taken into consideration, especially features that affect the patient directly. One of the most crucial areas that needs to be monitored is the level of dose prescribed by the x-ray beam. If there is too much, the patient could be harmed in the long run and if there isn't enough the radiographer wouldn't be able to capture a diagnostic image. This parameter is highly affected by the milliamperes (mA) and the exposure time of the beam. (Bushong, 2013) Collectively referred to as the mAs, this controls how many photons are shot across the cathode to the anode, and subsequently the amount of rays that are produced. The exposure time represents how long radiation is emitted from the x-ray tube. (Bushong, 2013) Too long and it is harmful, too low and it is not diagnostic. Digital X-ray TimerTo test that the exposure time was meeting HARP and SC35 standards a digital x-ray timer was used, shown in Image 1 above. This device recorded the length of the exposure time from start to finish, down to the millisecond. To set up the room a lead apron was placed over the detector to block any incoming radiation. The digital timer was placed on top of the apron, set to “0-20 sec”, and the tube was collimated to the top of the device. The technical factors were set to 80kVp at 200mA and 5mAs with a large focal spot. All factors were kept constant however after each exposure the mAs was doubled for the following 5 exposures. This test was first performed in room 3 and then in room 5. After each exposure the digital timer would display the amount of time it was irradiated, this value was recorded for every exposure. Once all the values were collected they were put into a chart and then compared to HARP and SC35 standards. Exposure Factors and Resultant Times |
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