Authors: Walter Huda Kent M Ogden
Publish Date: 2008/01/15
Volume: 38, Issue: 4, Pages: 415-423
Abstract
The computation of patient effective doses to children is of particular interest given the relatively high doses received from this imaging modality as well as the increased utilization of CT in all areas of medicine Current methods for computing effective doses to children are relatively complex and it would be useful to develop a simple method of computing pediatric effective doses for clinical purposes that could be used by radiologists and technologistsAdult E/DLP coefficients were obtained at 120 kV using the ImPACT CT dosimetry spreadsheet Patients were modeled as cylinders of water and values of energy imparted to cylinders of varying radii were generated using Monte Carlo modeling The amounts of energy imparted to the chest and abdomen of children relative to adults Ren were obtained Pediatric effective doses were obtained using scaling factors that accounted for scan length mAs patient weight and relative energy imparted RenE/DLP values were about 16 μSv/mGy cm for males and about 19 μSv/mGy cm for females Ren at 120 kV for newborns was 035 for the chest and 049 for the abdomen At constant mAs the effective dose to 6monthold patients undergoing chest CT examinations was found to be about 50 higher than that to adults and for abdominal examinations about 100 higherWe show two sample calculations below that serve three purposes 1 illustrate how our approach to pediatric CT body dosimetry can be implemented 2 demonstrate the relative importance of key parameters that affect patient dose and 3 provide values of pediatric effective dose when scanning with stateoftheart protocols that modify techniques as a function of patient sizeEa can be determined for an adult chest CT examination from consideration of the technique factors 120 kV/170 mAs as well as the pitch 15 and the adult scan length 35 cm from Table 3 Selection of these factors on the console of the CT scanner would show that this examination corresponds to a DLP of 377 mGy cm and assumes that the widest Xray beam width was used 40 mm Applying the female E/DLP conversion factor of 172 μSv/mGy cm Table 2 produces an adult effective dose of 65 mSv typical of the value expected for adult chest CT examinations
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