Dose Reduction Methods in Chest Computed Tomography

Introduction: Computed tomography is one of the most powerful tools for investigating thorax disease, because it shows progression of lung disease much clearer than chest radiography. Technical advances in CT scanners have led to some abilities for CT scanners such as coverage of larger volume, lower noise and ability for acquiring image in one respiratory phase. However, this will be accompanied by more radiation exposure to patient and research shows that CT gives higher exposure dose to patient in comparison with conventional radiography.1   Materials and Methods: In each computed tomography (CT), patient dose is dependent on the scan parameters. Scan parameters are included kV, mA, scan field of view (SFOV), rotation time, focal spot size, slice width and pitch. Also, shielding of sensitive organs such as breast which is not interest organ during chest CT scanning is one of the dose reduction methods. Furthermore, Type of scanner, methods and protocols of scanning, for example in multi-slice scanners there is some more cases like collimation, which effect on patient dose, and therefore all of these options should be adjusted, accurately. It is considerable that scan parameters such as reconstructed matrix and reconstruction algorithms have considered in this paper; however, these parameters do not impact directly on patient dose but they have some affects through changing the characteristics of the image indirectly. In this study twenty methods for radiation dose reduction in thorax CT were explained. Conclusion: According to the principle of ALARA, the aim of applying optimization techniques is to reduce the amount of receiving dose while maintaining image quality.