Determination of Optimum Exposure Factors at Constant Focal Film Distance (FFD) to Produce Quality Skull Radiographs with Minimum Absorbed Dose Using a Skull Phantom

Abstract

Aim: Image quality control as it applies to diagnostic Radiology is an effort to ensure that the diagnostic images produced are sufficiently provides adequate anatomical information for accurate diagnosis at the least possible exposure of radiation to the patient. The aim of this study was to determine the suitable range of kV and mAs at a constant FFD to produce skull radiographs of acceptable quality required by the Radiologist. Materials and methods: A locally made skull phantom with Perspex glass box and a real human skull from Anatomy department was used in this study. The phantom was placed on the X-ray table 120 cm from the X-ray tube head and two sets of exposures were made. First keeping mAs at 50 and varying the kV from 81-102 and the second keeping kV constant at 81 and varying the mAs from 32-80. Films were developed and 5 radiographs in each set were produced. A Raysafe Thin-X dose meter was fixed in front and at the back of the Phantom to determine the input and output dose respectively. The absorbed dose was calculated by the difference between input and output doses. The radiographs were assessed by a Radiologist to classify the image quality. Results and data analysis: The suitable exposure factors were found to be within the range of 81-85 kV with 50 mAs and 32-40 mAs with 81 kV to produce an acceptable quality skull radiograph. The absorbed dose varied from 1.451-3.503 mGy. Discussion and conclusion: The optimum image quality was obtained with 81 kV and 32 mAs at FFD =120 cm with minimum absorbed dose of 1.451 mGy.