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Comparison of radiation dose from intravenous urography and 99Tcm DMSA scintigraphy in children
1Department of Radiology, Great Ormond Street Hospital for Children NHS Trust, London, UK.
Insights
Comparing pediatric kidney imaging, intravenous urography (i.v.u.) and 99Tcm DMSA scintigraphy involve different radiation doses. While i.v.u. doses increase with age, DMSA doses remain consistent, suggesting i.v.u. may be less suitable for detecting renal scars in older children.
Area of Science:
- Pediatric Radiology
- Nuclear Medicine
- Radiation Dosimetry
Background:
- Intravenous urography (i.v.u.) and 99Tcm DMSA scintigraphy are key diagnostic tools for pediatric renal investigations.
- Previous radiation dose comparisons were limited by a lack of pediatric-specific data.
Purpose of the Study:
- To compare effective radiation doses from i.v.u. and 99Tcm DMSA scintigraphy in children.
- To evaluate the suitability of these techniques for pediatric renal imaging.
Main Methods:
- Utilized age-dependent entrance surface dose values from literature for radiographic procedures.
- Calculated effective dose for i.v.u. using "minimum" (4) and "average" (8) radiograph protocols.
- Used previously published 99Tcm DMSA dose estimates based on body surface area.
Main Results:
- 99Tcm DMSA effective dose remained consistently around 1 mSv for all pediatric age groups.
- Mean i.v.u. effective doses were comparable to DMSA for infants but potentially double for older children.
- i.v.u. demonstrated lower diagnostic sensitivity for detecting renal scars compared to DMSA.
Conclusions:
- Radiation dose from 99Tcm DMSA scintigraphy is consistent across pediatric ages.
- Intravenous urography effective doses can exceed DMSA doses in older children.
- The combination of higher radiation dose and lower sensitivity suggests limitations of i.v.u. for pediatric renal scar detection.
Abstract:
Intravenous urography (i.v.u.) and 99Tcm DMSA scintigraphy are possible alternative diagnostic techniques in paediatric renal investigation. Radiation dose comparisons between them have been complicated in the past by the lack of paediatric data. In this study, evaluations relevant to children are used to compare estimates of effective dose from the two techniques. For the radiographic procedures, standard operating parameters and representative age-dependent values of entrance surface dose were established from recent literature. Conversion factors relating effective dose to entrance surface dose and dose-area product are presented and used to obtain values of effective dose for single radiographs of abdomen, kidneys and pelvis. Suggested i.v.u. procedures consisting of four ("minimum") or eight ("average") radiographs were adopted to derive the effective dose for full i.v.u. examinations. 99Tcm DMSA dose estimates, taken from our published work using an administered activity schedule based on body surface area, are almost constant at about 1 mSv for all children. In comparison, mean i.v.u. doses based on the "average" number of radiographs are similar to DMSA doses for infants (< 1 year) but may be twice as high for older children. Although the differences between procedures at this level of dose do not in themselves provide grounds for preference, when coupled with the lower diagnostic sensitivity of i.v.u. they suggest limitations of this procedure for detection of a renal scar.