A method to derive appropriate exposure parameters from target exposure index and patient thickness in pediatric digital radiography

Little information exists concerning appropriate exposure and measuring overall patient dose in pediatric digital radiography. To establish a convenient method of appropriate exposure from target exposure index (EI) and thickness in pediatric digital radiography and estimate patient entrance-surface dose (ESD) and dose-area product (DAP) associated with chest, abdomen and pelvis radiography. A formula was deduced to calculate appropriate mAs changed with children's weight and height. EI was used to control image quality. With this formula, dose-optimized procedures were carried out. Data were collected from 180 pediatric examinations, including chest, abdomen and pelvis anterior-posterior (AP) projections. The children were divided into the following age bands: newborns (0-28 days), infants (28 days-2 years) and older children (2-7 years). In each age band, ten children were exposed with the calculated appropriate mAs and EI values were kept steady in appropriate range (referred as target group) and ten children were exposed to the factors routinely used in practice (referred to as the routine group). DAP to children was measured with a DAP meter, and ESD was calculated using measured DAP and data from the National Radiological Protection Board. Data were compared between groups. ESD ranges in the target group were 32-202 mu Gy (chest AP), 57-333 mu Gy (abdomen AP) and 52-372 mu Gy (pelvis AP). For every radiographic procedure, chi-square Student's t tests showed a significant difference in average ESD and DAP between the two groups (P < 0.005). Most ESD values from the routine group were two times higher than those from the target group. The study established a convenient method to set appropriate exposure parameters (mAs) to reach a target EI using the child's weight and height in pediatric radiography. By this method, ESD and DAP can be significantly reduced in children.