Uncertainty Measurement of kVp Output of the X-ray System using Spectrometry System

This study was carried out to determine the uncertainty of kVp output of the x-ray tube used in the calibration of non-invasive kVp meters. A non-invasive method was used to measure the spectrum of the x-ray output using Amptek XR-100T-CdTe spectrometry system. While an invasive high voltage divider (dynalyser) coupled to the x-ray system measures the true kilo voltage supplied to the x-ray tube with uncertainty of 2.5 % (k=2). The consistency of the kVp output was monitored daily at 9 points ranging between 40 kV-120 kV with interval steps of 10 kV from the dynalyser system. While the x-ray output spectrum of the 9 points were measured once a year. The uncertainty was determined from the consistency x-ray output, dynalyser system uncertainty, the spectrometry system accuracy, error and variation. The test results showed that kVp output measured by the dynalyser system everyday is consistent with coefficient of variations of not more than 0.89 %. The kVp output via dynalyser system and Spectrometry system shows good agreement with standard error of not more than 2.48 %. The total uncertainty of kVp output of the x-ray system using the spectrometry system is not more than 6.2 % (k=2). As a conclusion, the factors influencing the quality and quantity of the x-ray output also influence the uncertainty of the kVp output. (author)