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Biokinetic behavior of technetium-99m-DMSA in children
K Evans1, M F Lythgoe, P J Anderson
1Department of Medical Physics, Great Ormond Street Hospital for Children NHS Trust, London, United Kingdom.
Insights
This study analyzed technetium-99m dimercaptosuccinic acid (99mTc-DMSA) biokinetics in children. A single biokinetic model is suitable for radiation dosimetry in normal children, regardless of age.
Area of Science:
- Nuclear Medicine
- Pediatric Radiology
- Radiopharmacology
Background:
- Technetium-99m dimercaptosuccinic acid (99mTc-DMSA) is used for renal imaging.
- Understanding its biokinetics in children is crucial for accurate radiation dosimetry.
- Previous models may not adequately account for age-related variations.
Purpose of the Study:
- To investigate the biokinetic behavior of 99mTc-DMSA in pediatric patients.
- To determine if age-specific biokinetic models are necessary for radiation dosimetry in children.
- To compare 99mTc-DMSA uptake and excretion in children with normal versus abnormal renal function.
Main Methods:
- Intravenous administration of 99mTc-DMSA to 24 children (5 wk to 14.8 yr).
- Gamma camera imaging up to 30 hours postinjection.
- Estimation of absolute organ activities (kidneys, liver, spleen, bladder, knees, whole body) using conjugate counting.
- Measurement of renal uptake, elimination rates, and urinary excretion.
Main Results:
- In normal children, maximal kidney uptake was 42.4% with a half-time of 1.0 hr.
- Renal excretion was 18.0% at 24 hr, lowest in infants (<1 yr).
- Children with abnormal renal function showed reduced uptake and increased urinary excretion.
Conclusions:
- Age-dependent biokinetic factors are minimal in normal children, except for lower urinary excretion and knee uptake in infants.
- A single biokinetic model appears sufficient for radiation dosimetry in normal pediatric populations.
- Findings support the use of a generalized model for 99mTc-DMSA dosimetry in children.
Unlabelled:
After intravenous administration of 99mTc-DMSA, biokinetic data were collected from studies on 24 children aged from 5 wk to 14.8 yr (15 normal and 9 with renal pathology).
Methods:
Patients were imaged with a gamma camera up to 30 hr postinjection and the absolute activities in the kidneys, liver, spleen, bladder, knees and whole body were estimated using an attenuation-corrected conjugate counting technique. Renal uptake and elimination rates and urinary excretion of radioactivity were also measured.
Results:
In children with normal renal function, maximal kidney uptake was 42.4% +/- 5.4% and was taken up with a half-time of 1.0 +/- 0.2 hr. Renal excretion amounted to 18.0% +/- 4.4% at 24 hr and was lowest in children aged less than 1 yr. In children with abnormal renal function, apart from the expected reduction in renal uptake there was evidence of wider variations in uptake rate and increased urinary excretion. Mean uptakes in liver and spleen were approximately 5% and 2%, respectively, in all patients and uptake in knees, assumed to reside in the metaphyseal growth complexes, was 1.4%.
Conclusion:
In children with normal renal function, there was little evidence of age-dependent biokinetic factors other than reduced urinary excretion and lower uptake in knees in children aged less than 1 yr. The results therefore suggest that a single biokinetic model may suffice for radiation dosimetry purposes in normal children irrespective of age.