The Influence of Anti-scatter Grid Usage for Knee Computerized Radiography

Aims: This experimental study investigated the effect of using an anti-scatter grid in computerized knee radiography (CR) on image quality (IQ) and patient surface radiation dose (Equivalent Surface Air Kerma – Ka,e), measured with an ionization chamber.

Place and Duration of Study: The experimental study was conducted between February 2024 and April 2024, in the radiodiagnosis laboratory belonging to the Medical Physics and Radiology Technology courses at the Franciscan University (UFN) in the city of Santa Maria, Rio Grande do Sul.

Methodology: Utilizing a semi-anatomical knee phantom to simulate clinical examination conditions, ten images were acquired, with five obtained using technique 1 (70 kV, 200mA, and 20mAs) and another five with technique 2 (70 kVp, 200mA, and 5 mAs), with and without an anti-scatter grid, respectively. The phantom images were digitized in a CR system and quantified using a publicly available automatic analyzer software based on histograms and regions of interest (ROI), defined by signal and noise. The obtained results were used to calculate the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and radiographic contrast (RC), considered IQ descriptors.

Results: As a selection criterion, the percentage deviation (D%) was chosen, considering technique 1 as the reference concerning technique 2. It was observed that technique 1 showed an SNR 1.20%, RC 3.86%, and Ka,e 73.68% higher than technique 2; on the other hand, technique 2 indicated a CNR 4.76% higher compared to technique 1.

Conclusion: It is concluded that technique 2 without an anti-scatter grid may be preferable when considering the principle of optimization, where the dose is significantly reduced without a significant loss in IQ descriptors.