Program Information
Analyzing Portable Abdomen Radiography Techniques to Guide Size-Specific Pediatric Protocol Development
A Sanchez*, I Reiser , T Baxter , Y Zhang , Z Lu , K Feinstein , The University of Chicago, Chicago, IL
Presentations
SU-F-702-5 (Sunday, July 30, 2017) 2:05 PM - 3:00 PM Room: 702
Purpose: To investigate trends in technique factors, exposure index (EI), and patient size for exams performed by technologists experienced in pediatric imaging and to design part-thickness-dependent protocols for portable pediatric abdomen radiography performed by technologists without dedicated pediatric training.
Methods: Beginning October of 2016, technologists performing portable pediatric abdomen radiographs in our children’s hospital recorded source-to-image distance (SID) and caliper-based abdomen thickness measurements. Technique factors (kVp, mAs) and EI were obtained from the portable units’ exposure logs. Output measurements were used to convert kVp and mAs to exposure output in mR normalized to 40in. Of roughly 1,000 exams for which data were acquired, to date roughly half have been fully incorporated into our database. These exams were performed with our current age-based protocols.
Results: While median EI was relatively constant across patient thickness, variability of EI (fractional standard deviation) was roughly 40-50% for a given thickness. Variability of tube output and SID were roughly 12% and 25%, respectively after removal of outliers. The 12% variation in SID (from roughly 31-39”) corresponds to a 20% variation in exposure at the detector. SID information was used to normalize the observed EI measurements to a fixed SID in order to investigate whether this was a major contributing factor to EI variability. Finally, we found that kVp and mAs were different from default in 70% of exams.
Conclusion: Compensating for variations in SID was only found to reduce EI variability for the smallest patients of <4cm thickness. However, a chart of mAs change to compensate for SID could be beneficial in cases where SID is constrained by the use of ancillary equipment. Constancy of EI suggests that experienced pediatric technologists inherently adjust technique factors based on patient size. This validates the usability of these data for development of size-specific technique factor selection.
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