Single-slice helical CT scanners were introduced in the 1980's and multislice CT scanners in the 1990's, which allows a larger section of the body to be scanned in a smaller period of time (Wesolowski, 2005).
From the practical perspective, the benefits of CTs are immense. However, CT scans involve higher doses of radiation than the conventional x-ray procedure (Smith-Bindman et al, 2009). CT contributes a large dose towards medical radiation, and is the main source of man- made radiation excluding natural background radiation (Wiest, 2002). There is concern about the exposure of radiation in children and adult population and the subsequent long-term cancer risks. CT procedures cause high doses of radiation to be absorbed through the skin, in the range of 20-30 mGY (2-3 rads) (Wiest, 2002). There is greater concern for the pediatric population because they are more sensitive to radiation exposure than the adult population (Brenner, 2007). Children are more prone to exposure because they have a larger proportion of dividing cells and the tissues of children are up to 10 times more radiosensitive than adults (Brenner, 2007). Chwals et al., found that CT examinations of the head, abdomen and pelvis routinely performed in pediatric trauma patients exposed them to 50 times the standard yearly dose of background ionizing radiation (Chwals, 2008). Radiation exposure in the adult population is low but still a concern. Broder suggests that in adults, it reaches its threshold in the 40's and then slowly decreases (Broder, 2006).
Due to the repetitive radiation exposure and adverse effects associated with it, the operators of CT are expected to possess a concrete knowledge and practical understanding how to reduce the radiation dose patients receive to acceptable minimum (Manghat et al, 2005). Similar concerns regarding radiation exposure and cancer risks have propelled the medical community to implement protocols to lower the radiation dose in children, by adjusting the machine settings without compromising important information (Brenner, 2007). Other measures include reducing repeat CTs and decreasing unnecessary CTs by ensuring that any additional CTs ordered by a physician will only benefit the patient (Brenner, 2007). According to Manghat et al (2005), CT operators can utilize the variety of strategies to reduce radiation exposure such as the use of bismuth shields to protect organs sensitive to radiation, adjusting the machine settings using automatic exposure control (AEC), the tube voltage (kVp) reduction, decreasing the pitch and the tube current-time product (mAs).
Practically, educating doctors regarding the risks associated with radiation is an important factor to allow physicians to make informed decisions when considering radiological tests (Thomas, 2006). Lee and colleagues highlighted this in a study that found 75% of Emergency Department (ED) physicians and radiologists underestimated the risks associated with radiation from CT examinations (Thomas, 2006). Recognition of the potential cancer risks by the medical community has pressed CT manufactures to implement programs to allow adjustment of the dose with respect to the child's body mass (Chwals, 2008). As of 2003, the majority of hospitals in developed countries reported implementing some programs to reduce radiation exposure in children, though still many hospitals have yet to implement these changes