Considerations on the measurement of practical peak voltage in diagnostic radiology
| Autor: | R López-Callejas, J.O. Pacheco-Sotelo, J S Benítez-Read, F J Ramírez-Jiménez |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Quality Control
Accuracy and precision medicine.medical_specialty business.industry X-Rays High voltage General Medicine Reference Standards Sensitivity and Specificity Kerma Electricity Absorbed dose Calibration Medicine Waveform Humans Radiology Nuclear Medicine and imaging Radiology Oscilloscope business Half-value layer Mathematics Voltage |
| Zdroj: | The British journal of radiology. 77(921) |
| ISSN: | 0007-1285 |
| Popis: | An evaluation of the non-invasive measurement of the practical peak voltage (PPV) in the quality control of X-ray units used in diagnostic radiology was carried out. Two instruments were employed: the PTW Diavolt Universal Tester with readings in PPV and the Waveform Tester for X-rays (WATEX) prototype proposed here, which uses a PIN structure (P-type diffusion, Intrinsic region, N-type diffusion) photodiode as a sensor. The reference for the measurements was the voltage signal obtained in an oscilloscope from an invasive high voltage divider in order to verify the accuracy and precision of the measurements. The readings of the PPV in the Diavolt show a systematic error between 1% and 8%, always being less than the real value. An explanation for this difference is proposed, based on the relation between the effect of the X-rays in the film and the response of the sensor to the product of the applied voltage to the X-ray tube (peak voltage kVp), and the anode current. This explanation was confirmed using the WATEX waveform tester. Digital radiography is becoming a standard technique, due to better quality of images and reduced patient dose. In order to avoid unnecessary radiation dose to the patient, recent experience (1) has shown that there is a need to consider many factors, some of which were not considered in analogue techniques. It is important to keep the radiation doses to patients at a minimum, because the use of X-rays in medicine for diagnosis represents the largest man-made source of public exposure to ionizing radiation (2). Quality control of X-ray units is necessary to ensure good performance and minimum dose to patients. In quality control, several parameters are measured. According to several recommendations (3, 4), the main parameters are: (a) high voltage applied to the X-ray tube; (b) exposure time; (c) efficiency of the X-ray unit, calculated as the ratio of the absorbed dose to the product of current and time (Gy/mA-s); (d) the quality of the beam, measured as the half value layer (HVL) using aluminium filters; (e) the air kerma rate (Gy min 21 ); and (f) the |
| Databáze: | OpenAIRE |
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