The Use of Extended Focus-to-Film-Distance (FFD) for Dose Reduction in Radio-Diagnostic Examination of the Skull

Abstract

The method of increasing the focal to film distance technique was used in this work to determine the input dose and the absorbed dose of the radiograph using the Perspex phantom of an adult skull. The film quality was also analyzed by a radiologist and the best film quality was obtained in the X-ray department, at the University of Jos Teaching Hospital (JUTH). The input doses obtained in this work are all below the diagnostic reference level of 5mGy recommended by the IAEA and the European Commission for the skull (AP, PA) x-ray examination. In all the irradiations, FFD of 90cm appears to give a higher (4.14mGy) dose to the patients while a lower dose (1.67mGy) was obtained at FFD of 130cm. The absorbed doses obtained in this work also appeared to be reducing greatly from 3.78mGy at FFD 90cm to 1.44mGy at FFD 130cm. The five radiographs of the skull were analyzed by two radiologists and the best radiograph for the skull anterior-posterior is at FFD 110cm with a minimal absorbed dose of 2. 17mGy.The value of the absorbed dose for the best radiograph was compared with the reference value 3mGy for the skull (AP, PA) X-ray radiography by ICRP and found to be below the reference value. The results obtained from this work show that the best radiograph for skull AP will be obtained at a Focal-film Distance of 110cm when a constant tube voltage is set at 90kVp and 50mAs with a minimal absorbed dose of 2.17mGy and radiation protection is optimized.