Avaliação da interferência da variação de tensão na qualidade de imagens mamográficas

Abstract

Breast cancer ranks as the second most common malignancy among women in Brazil and is one of the leading causes of global female mortality. Mammography stands out as a vital diagnostic method for early cancer detection, which is crucial for lowering mortality rates and enabling less invasive interventions with higher chances of successful treatment. This study aims to evaluate the impact of X-ray tube voltage variation on the quality of mammographic images, within the limits set by Brazilian regulations. Using the Piranha RTI multiparameter meter, tests for tube voltage accuracy and reproducibility were performed, and images were captured with the Cleopatra Phantom, a mammographic simulator designed to mimic real breast tissues. The methodology included image acquisition at different tube voltages (33 kV and 35 kV), with automatic mAs adjustment, followed by a quantitative image quality analysis using MATLAB. Metrics such as the mean and standard deviation of pixel intensities, Signal-to-Noise Ratio (SNR), and Structural Similarity Index (SSIM) were calculated to assess image uniformity, noise levels, and structural degradation. The quality control tests were conducted in compliance with the Instruction Normative 92 and RDC Resolution 611/22, which govern dose and voltage parameters in mammography. The results indicated that a 5.71% increase in tube voltage, while permissible under current regulations, led to a significant increase in radiation dose without notably improving image quality, as shown by the SNR and SSIM values. Images taken at 33 kV and 35 kV exhibited minimal differences in mean intensity and contrast; however, analysis of exposure and exposure rate values revealed a marked increase in administered dose. The study concludes that, even within regulatory limits, maintaining strict quality control is essential to minimize patient exposure, adhering to the ALARA principle (As Low As Reasonably Achievable) to ensure patient safety without compromising diagnostic accuracy.