Influência da variação do ASIR (Adaptative Statistical Iterative Reconstruction) no ruído da imagem de tomografia computadorizada para altas tensões

Abstract

Computed tomography has undergone major advances in terms of the equipment used in diagnostic practice, directly influencing radiation levels for the patient. It is essential to optimize the techniques that must be used to comply with the ALARA (As Low As Reasonably Achievable) radiation protection principle. The study in question aimed to study the relationship between ASIR (Adaptive statistical iterative reconstruction) and image noise. Central images of a homogeneous water phantom were obtained in a 20 mm scan using a General Electric Lightspeed VCT 64-channel tomograph in helical acquisitions, with a rotation time of 0.5 seconds, Pitch 0.984:1, and slice thickness of 0.625 mm, all these parameters constant, varying the voltage in two distinct values: 120 and 140 kV using the automatic current by the CAE (Automatic Exposure Control), ranging from 50 to 675 mA (120 kV) and from 50 to 610 mA (140 kV), the minimum and maximum values ​​allowed for each voltage, respectively. The image noise was determined using the free software ImageJ. Through the analysis of the data obtained, the percentage variation of noise in the image was compared based on the ASIR value of 10%, concluding that there is a variation of approximately 50% when compared with the ASIR values ​​(100%) in both voltages. It is necessary to evaluate the dose in future work to better utilize the relationship between dose and image quality.