Computed tomography (CT) is currently the most important contributor to medical radiation exposure, and pediatric and young adult CT studies raise special concern. A young age and high cumulative effective doses due to repeated CT during follow-up increase the risk of detrimental effects of radiation. Thus, the radiation dose, image quality, and the effects of parameter changes to these two need to be estimated to optimize CT examinations. 

Thesis examines radiation doses as expressed by computed tomography dose index (CTDI), organ doses and effective doses among pediatric, adolescent and young adult patients. The influence of the CT scanner, patient size, and intravenous contrast agent were studied with regard to the radiation dose and image quality, and the effects of protocol parameter changes were studied to establish a more effective imaging protocol for the assessment of acute appendicitis. Radiation doses were evaluated by phantom measurements using dose monitoring software and dose calculation software. The image quality was evaluated by measuring the contrast to noise ratio and by visual assessment by radiologists. 

A wide deviation of CT doses was found, despite homogenous cohorts and similar imaging indications. The deviation resulted from differences in the CT devices and non-optimized protocols. High effective doses cumulated during the follow-up of patients with testicular cancer. In the assessment of acute appendicitis, the radiation dose may be reduced, without decreasing image quality, by appropriate protocol adjustments. The large variations in radiation doses and the high cumulative effective doses emphasize the need for setting parameters carefully and for harmonized practices. There is also a need for improved dose monitoring, which may uncover non-optimized protocols.