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Solid anthropomorphic infant whole-body DXA phantom: design, evaluation, and multisite testing
Roman J Shypailo1, Kenneth J Ellis
1US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
Insights
A new dual-energy X-ray absorptiometry (DXA) phantom for infants shows good reproducibility. However, significant differences between DXA instruments emphasize the need for cross-calibration in multicenter infant body composition studies.
Area of Science:
- Medical imaging
- Biomedical engineering
- Pediatric research
Background:
- Dual-energy X-ray absorptiometry (DXA) is crucial for quality control and cross-calibration.
- Existing phantoms are not designed for infant whole-body scanning.
- Accurate infant body composition assessment is vital for pediatric health studies.
Purpose of the Study:
- To develop and evaluate a novel phantom for infant whole-body DXA scanning.
- To assess the comparability of DXA instruments in infant body composition analysis.
- To address the lack of specialized phantoms for pediatric DXA applications.
Main Methods:
- A custom phantom was fabricated using polyvinyl chloride (PVC), nylon mix, and polyethylene to mimic infant bone, lean tissue, and fat.
- The phantom underwent short- and long-term repeatability scans.
- The phantom was cross-scanned across six different sites using Hologic DXA instruments.
Main Results:
- The phantom demonstrated good short- and long-term reproducibility for lean mass, bone, and fat.
- Material compositions showed slight under- or overrepresentation of target tissues (lean: -5%, bone: -12%, fat: +30%).
- Significant inter-instrument variability was observed in bone mineral content, bone density, fat, and lean mass measurements.
Conclusions:
- The developed infant phantom effectively emulates key body tissues and exhibits good reproducibility.
- Substantial differences between DXA instruments necessitate rigorous cross-calibration for multicenter infant body composition studies.
- This phantom serves as a valuable tool for improving the reliability of pediatric DXA assessments.
Background:
Dual-energy X-ray absorptiometry (DXA) requires phantoms for quality control and cross-calibration. No commercially available phantoms are designed specifically for whole-body scanning of infants.
Methods:
We fabricated a phantom closely matching a 7-kg human infant in body habitus using polyvinyl chloride (PVC), nylon mix, and polyethylene for bone, lean tissue, and fat, respectively, for evaluating the comparability of instruments used in studies on infant body composition. We scanned the phantom multiple times for short- and long-term repeatability and then shipped it to six other sites for comparison scans. All instruments were Hologic Delphi or Discovery models. Scan analyses were in-house procedures (Hologic V12.1).
Results:
Short- and long-term results were not significantly different. Nylon mix underrepresented expected lean mass values by 5%, PVC underrepresented bone by 12%, and polyethylene overrepresented fat by 30%. Precision values were as follows: lean mass ≈ 3%; bone ≈ 3.5%; and fat = 5.5-7.5%. Instruments differed significantly for bone mineral content and density results in most instances. Three instruments differed in fat and lean mass. The two Hologic models differed significantly in all compartments except bone density.
Conclusion:
The phantom design came close to emulating bone, lean tissue, and fat and showed good reproducibility. Significant differences among various DXA instruments highlight the necessity of cross-calibration for any multicenter studies.
