The performance of a NERO 8000 non-invasive x-ray beam analyser when measuring tube voltage under fluoroscopic conditions.
A NERO 8000 non-invasive x-ray beam analyser was examined under fluoroscopic conditions with respect to the measurement of tube voltage. An invasive measurement of tube voltage was performed concurrently to test the accuracy of the NERO device over a range of tube voltages and currents. The data indicated that for the NERO 8000 the accuracy of kVp average measurement is dependent on input doserate. With the tube current set to 1 mA the doserates ranged from 2.1 to 6.5 mGy/min over the range of tube voltages measured. The associated kVp average measurement errors ranged from 6 to 28%. At 5 mA the doserates ranged from 20.4 to 66.0 mGy/min and the associated errors ranged from 0 to 3%. A possible explanation for the drop in accuracy of kVp measurements at low doserates is a decreased signal to noise ratio. The kV waveforms from inaccurate measurements appeared noisier than waveforms from more accurate measurements. NERO may be interpreting noise spikes as voltage readings and including them in the kVp average calculations, causing an erroneously high kVp average reading. The data from this experiment suggest that when performing non-invasive measurements of tube voltage accuracy in fluoroscopy mode, the doserate must be taken into consideration.
Burrage
J W
JW
Department of Medical Physics, Royal Perth Hospital, WA. john.burrage@health.wa.gov.au
D055592:Biophysical Phenomena; D001703:Biophysics; D005471:Fluoroscopy / Q000295:instrumentation* / Q000592:standards; D006801:Humans; D011785:Quality Assurance, Health Care; D013679:Technology, Radiologic