Kilovolt peak (kVp) is the main factor for controlling the average energy of the beam. The higher the kVp, the greater the potential difference in the x-ray tube allowing more photons to hit the anode. Optical density, image contrast and patient dose is effected by kVp. (Papp, 2011) The kVp accuracy lab was a quick experiment to determine the accuracy of the machine. It was preformed in both room 3 and room 5. To start a lead apron was placed on the table and the kVp meter was placed on the lead with the x-ray tube centred to the kVp meter sensor. The SID was set at 70cm and collimated to the entire sensor. The kVp was exposed at three different settings of 60, 81, and 102 and each were taken with 5 mAs and 16 mAs. Three exposures were taken at each kVp and mAs setting and the kVp values detected were displayed and recorded. The chart below displays the values obtained at the different settings. All of the values were within the standards in SC35 (2008), HARP (1990) and Papp (2011). According to SC35 (2008) the range is to be within 10% and HARP requires the range to within 8%. If the values were outside of the standards the image quality would be effected. Higher kVp will give a lower contrast because there is more scatter and more penetration therefore more shades of grey will be visible. This is the opposite for a low kVp; the contrast will be higher. Variations in kVp may be due to variations in the line voltage supplying the x-ray generator, by faulty high voltage cables, or by problems with the autotransformer/kVp selection circuitry. (Papp, 2011) Room 3Room 5 |