Possibilities of Reducing Radiation Dose in Computed Tomography Examinations in Various Age Groups Using an Iterative Model-Based Reconstruction Technique

Abstract

Aim: To determine whether iterative model-based reconstruction (IMR) technique can preserve computed tomography (CT) image quality when the radiation dose is reduced to 20% of the original value. Methods: CT examination of the neck, mediastinum, or stomach was performed using standard protocols with a Philips Healthcare MDCT 64. Fifty imaging studies were evaluated. The patient’s set was divided into three groups: Young, Preadolescent, and Adult. Four experienced evaluators assessed the CT scans reconstructed using filtered back projection (FBP) and IMR technique (using the L1BR, L2BR, and L2BSP levels) at a 100% dose and at a dose reduced by 80%. The dose was reduced by a decrease in milliampere seconds (mAs). Image noise, artifacts, anatomical details, sharpness, low-contrast resolution, general impression of the reconstructed image, possibility of influencing the description, and possibility of influencing the examination’s conclusion were assessed. FBP at 100% of mAs was always used as the basis for comparison. Decrease in a parameter meant a negative point score while an improvement was marked as positive. Subsequently, objective measurement of image quality was also performed. Results: The greatest improvement in image quality (relative to the quality of images reconstructed using FBP with 100% dose) was achieved using IMR L2BR reconstruction, which can be recommended as optimal. The IMR L2BR reconstruction method was statistically demonstrated to have the best performance among the tested methods in suppressing noise and artifacts. In relation to the selected indications, this method allows a reduction in dose by as much as 80%. The effect of IMR was less marked among the youngest patients than in the remaining two patient groups. Conclusion: The study demonstrated that use of the IMR technique preserves diagnostic indications even with a markedly reduced dose in CT examinations of the neck, thorax, and abdomen in various age groups.Aim: To determine whether iterative model-based reconstruction (IMR) technique can preserve computed tomography (CT) image quality when the radiation dose is reduced to 20% of the original value. Methods: CT examination of the neck, mediastinum, or stomach was performed using standard protocols with a Philips Healthcare MDCT 64. Fifty imaging studies were evaluated. The patient’s set was divided into three groups: Young, Preadolescent, and Adult. Four experienced evaluators assessed the CT scans reconstructed using filtered back projection (FBP) and IMR technique (using the L1BR, L2BR, and L2BSP levels) at a 100% dose and at a dose reduced by 80%. The dose was reduced by a decrease in milliampere seconds (mAs). Image noise, artifacts, anatomical details, sharpness, low-contrast resolution, general impression of the reconstructed image, possibility of influencing the description, and possibility of influencing the examination’s conclusion were assessed. FBP at 100% of mAs was always used as the basis for comparison. Decrease in a parameter meant a negative point score while an improvement was marked as positive. Subsequently, objective measurement of image quality was also performed. Results: The greatest improvement in image quality (relative to the quality of images reconstructed using FBP with 100% dose) was achieved using IMR L2BR reconstruction, which can be recommended as optimal. The IMR L2BR reconstruction method was statistically demonstrated to have the best performance among the tested methods in suppressing noise and artifacts. In relation to the selected indications, this method allows a reduction in dose by as much as 80%. The effect of IMR was less marked among the youngest patients than in the remaining two patient groups. Conclusion: The study demonstrated that use of the IMR technique preserves diagnostic indications even with a markedly reduced dose in CT examinations of the neck, thorax, and abdomen in various age groups.