Over the last few decades, MDCT(multidetector computed tomography), cardiac imaging, CT perfusion techniques, high-pitch CT, and dual-energy CT have been introduced to clinical practice, increasing the overall amount of radiation applied. There are two types of approaches in accordance with the "as low as reasonably achievable (ALARA)" principle in MDCT. One of them is related to new technology products and different imaging techniques such as dose modulation along the x-, y-, and z-axes (anatomical tube current modulation, ECG-controlled tube current modulation or dynamically adjustable pre-patient collimation of the X-ray beam in the z-axis direction, iterative reconstruction technique. The other strategy is individualized screening-dose protocols based on body size. However the radiologist is facing the challenge of providing diagnostic image quality at the lowest radiation dose.