The optimization of any contrast medium injection protocol should be aimed at achieving the best arterial and/or parenchymal enhancement according to the clinical indication. Arterial and parenchymal enhancements influence the accuracy of the MDCT examination and are generally affected by different kinetics. Arterial enhancement is determined mainly by the iodine dose delivered per unit of time and parenchymal enhancement by the total iodine dose. However, both are significantly related to patient-specific factors, such as body size, cardiac performance, gender, and age. Moreover, the goal of any MDCT examination is to achieve the best image quality using the lowest volume of contrast medium (CM), because most adverse CM reactions are a consequence of the total iodine dose administered to the patient.