Abdominal spiral CT in children: which radiation exposure is required?

We decided to test to what extent dose reduction is possible in abdominal s piral computed tomography (CT) in young children without loss of anatomic d iagnostic information. A retrospective study was performed of 30 abdominal CT examinations of children aged 3 months to 7 years. These were divided in to two groups: group A with reduced radiation exposure (tube current 50 mA, CT dose index CTDIFDA less than or equal to 0.83 mGy) and group B with sta ndard radiation exposure (tube current greater than or equal to 100 mA, CTD IFDA greater than or equal to1.66 mGy). Image quality was assessed using a four-part scale ('excellent', 'good', 'sufficient'. 'poor') on visual image impression and visibility of 32 anatomical details. Five experienced radio logists read the CT scans independently who were blinded to the examination parameters. Differences in ranked data were evaluated with Wilcoxon's rank sum test. No difference between groups A and B was observed in visual imag e impression. Detail visibility was significantly lower in group A, but the differences were limited to right upper quadrant structures (portal vein, common bile duct, pancreatic head, adrenals) and to arterial branches. Sign ificant differences in visibility rated as 'poor' were only found for the h epatic, splenic and renal arteries; all other structures showed no differen ce between groups A and B. A protocol with reduced radiation exposure (50 m A, CTDIFDA less than or equal to0.83 mGy) allowed the demonstration of most anatomic structures in abdominal spiral CT in young children. For the prec ise demonstration of small details (e.g. structures of the right upper quad rant), a protocol with standard radiation exposure (greater than or equal t o 100 mAs) was superior.