الفهرس 
Introduction and literature reviewOnly 14 pages are availabe for public view
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Abstract
An efficient quality assurance (QA) program in X-ray mammography facilities is difficult to implement and must be developed to coordinate practices and everyday operations. It is critical to identify the problems and difficulties of daily practices and evaluate the requirements needed to develop a perfect system. In this study, the physical parameters at three x-ray mammography units were tested. These parameters were: reproducibility and accuracy of kVp, half-value layer (HVL), tube output and compression test. Also, the performance of two mammography units using different target/filter combinations and tube voltage has been assessed. The Target filter combinations were Molybdenum/Molybdenum (Mo/Mo), Molybdenum/Rhodium (Mo/Rh), Rhodium/Rhodium (Rh/Rh) and Tungsten /Rhodium (W/Rh). Contrast-to-Noise Ratio (CNR) and mean glandular dose (MGD) were observed at the mammography system and recorded. CNR were measured using ACR mammography accreditation phantom.
According to IAEA guidelines, the acceptable limit of the percentage of deviation in kVp accuracy is ± 5%. By comparing our results with the limiting value, it is observed that unit 1 with Mo/Rh target filter combinations at 25, 26 and 27 KVp and unit 2 with W/Rh target filter combinations at 27 KVp did not pass the kVp accuracy test. 28 KVp is recommended for clinical use as per IAEA guidelines.
The guidelines of the IAEA and the European protocol show that the linearity of two-tube output at consecutive mAs must be within ≤±10%, The results showed that the linearity for unit 1 with three target filter combinations and unit 2 with w/Rh combinations are in agreement with the values of the reference level, but unit 3 with Mo/Mo does not occupy the limitation value.
The analysis of the results showed that the variation of the X-ray tube voltage has a significant effect on the CNR value, The greater X-ray tube voltage, the greater the CNR value. At a constant x-ray tube voltage, image contrast was proportional to (mAs). This will permit the image contrast to noise ratio (CNR) to be modified by changing the mAs.
from the data obtained, the available Quality Assurance (QA) programme in hospitals which applied according to the requirements of the Egyptian regulatory authority at the Ministry of Health was evaluated and more efforts are needed to increase the management of breast cancer with improves radiological safety of patients.
This study provides useful guidance to develop the Egyptian quality assurance (QA) program in X-ray mammography units and take all the corrective actions needed to optimize dose to patients.