With the advance of technology and the emergence of multi-slice CT scans (MDCT), the use of CT scans in medical diagnosis has increased significantly. On the other hand, the installation of CT scanners has also increased. Therefore, considering that the highest radiation dose received by the public from medical sources is related to CT scan and also stochastic effects caused by radiation such as cancer, it is important to pay attention to dose management in CT and optimization of protocols. CTDI & DLP are the two main indexes of dose expression in CT scan, and scan parameters such as kVp, tube current (mAs), Pitch factor, scan length, and the use of automatic exposure control (AEC) affect the dose by influencing these two indicators. And finally, with the use of these indices and coefficients related to tissue radiation sensitivity, the effective dose from CT examination can be calculated and compared with other imaging modalities. The image quality indicators that should be included in a proper imaging are parameters such as Noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). In CT scan protocols, scan parameters must be carefully selected so that these indicators are at an optimal level. The optimal limit of these indicators will be different according to the
diagnostic application of CT scan. Of course, according to the optimization and justification principles, a compromise should always be made between the image quality and the radiation dose, so that both diagnostic quality and radiation protection are considered.