Evaluation of the use of anti-scatter grids in adult knee radiography

Abstract

Purpose: This study aims to establish the thickness threshold for the use of an anti-scatter grid in adult knee radiography using digital radiography by varying the influencing radiographic and anatomical parameters. Objectives: The objectives were to acquire x-ray images of the knee anatomy with varying thicknesses. Different radiographic parameters (kVp and use of anti-scatter grid) were used. Radiation doses were measured, and image evaluation was carried out to assess when anti-scatter grid was beneficial. Methodology: The first phase of the study consisted of acquiring the x-ray images using an anthropomorphic phantom. The thickness of the knee was increased by 2cm increments from the original thickness of 10cm to 16cm. The tube voltage was altered starting from 60kV to 80kV. For each tube voltage setting, an image with an anti-scatter grid and an image without a grid were obtained. The second phase consisted of image quality assessment using subjective image evaluation, performed by five participants. The subjective image evaluation was done using Visual Grading Analysis (VGA) based on five image quality criteria. Results: The results of the study show that radiation dose decreased with the removal of the antiscatter grids. The average percentage decrease in dose area product (DAP) was 72.1%. Whilst for milliamperes per second (mAs), the average percentage decrease was 73.1%. The results of the VGA study show that the images taken with an anti-scatter grid have better image quality. However, for thicknesses between 10cm and 12cm, the increase in image quality was not statistically significant (p>0.05). Conclusions: Projections of the adult knee between 10 to 12cm should be taken without an anti-scatter grid, since the radiation dose is reduced without significantly affecting image quality. For thicknesses 14cm and 16cm, an anti-scatter grid should be used due to significant improvement in image quality, however, the radiation dose to the patient increased.