Mammography is a modality in radiography that takes soft tissue images of breast tissue. Since mammography is used to diagnose breast cancer, the images must be of very high quality so that tissue abnormalities are visible. There are many different quality control tests that must be performed such as, automatic exposure control (AEC), focal spot condition, uniformity, and reproducibility. If values deviate from the standards, there is a decrease in image quality. Soft tissues already have a very low subject contrast, so the images must be of the highest quality to ensure the interpreting physician can see very slight abnormalities in the tissues (Papp, 2011). If the amount of exposure given to a patient is inconsistent, a lesion in a patient’s breast could be missed or they could be misdiagnosed. This lab focused on reproducibility in mammography and was done to ensure the mammography unit is reproducing values within acceptable limits. Reproducibility should always produce the same intensity of radiation each time the same set of technical factors is used (Papp, 2011). The experiment required a mammography x-ray unit, an exposure meter and a lead sheet. The exposure meter was placed on the mammography unit and a lead sheet was placed underneath the detector. The collimation was adjusted to include the entire sensor. Ten exposures were taken of the dosimeter at 5 mAs and 25 kVp and the value on the dosimeter was recorded. These values can be found in Table 1 below. Each exposure was taken at least 30 seconds apart. According to Safety Code 33 (2013), the coefficient of variation of any 10 consecutive exposures should be no greater than 0.05. It also states that the mean of the 10 exposures should be within 15 percent of the 10 radiation measurements. In Papp (2011), it says the coefficient of variation of reproducibility should be equal to or less than 0.02. Using the values obtained during the experiment in Table 1 and the equation found below, the coefficient of variation was calculated to be 0.0201. This value is within the standards in Safety Code 33 (2013) as well as each exposure is within 15 percent of the average. On the contrary, the coefficient of variation is slightly greater than the standards stated in Papp (2011). The coefficient of variation could be slightly off from the standards because of wiring issues, tube malfunctions, or faults from the technologist working the machine such as letting go of the exposure button too soon. The coefficient of variation was calculated using the following equation: where, Xi = ith exposure measurement
X bar = mean value of exposure measurements n = number of exposure measurements
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