The purpose of the CR uniformity quality control test was to test the uniformity of the CR processor. A dosimeter was put on the floor with the tube perfectly perpendicular to it. The SID was set to 180 cm and the collimation was adjusted to cover the surface of the dosimeter. Filtration was added on the collimator to a value of 0.3mm Cu. A 1mm aluminum sheet was also taped under the collimator light after all the adjustments were done. The kVp was set to 80 and the mAs was adjusted until the output of the dosimeter read 10mR. The mAs value that achieved this was 4. After the value was found, the dosimeter was replaced with a 10"x12" CR cassette and the 1mm aluminum plate was removed. The SID was once again changed to 180 cm and the collimation was fixed to cover the surface of the cassette. The sheet of aluminum was re-taped onto the collimator and the cassette was exposed using the same exposure factors. The cassette was then processed using a “pattern” setting with image enhancement options off.
The image was assessed to see if the CR processing was uniform. The window width and level were adjusted to make sure the entire image was the same. However the image that was processed during the lab showed some light streaks when the brightness and contrast were adjusted. The streaks showed that the image could not be considered uniform. An SID of 180 cm was used to try and limit the anode heel effect. This was to try and get the beam to strike the cassette with even intensities over the entire image receptor. The AAMP states standards for qualitative and quantitative criteria. The accepted qualitative criteria is a developed uniform image without any artifacts. The quantitative criterion for acceptance is pixel value standard deviation (PVSD) to be less than 20 for a single screen, and exposure index standard deviation (EISD) to be less than 20. This would mean the image taken during this test would not pass the standards because artifacts were seen.
0 Comments
|
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |