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Variations in normal anatomy and influence on dose calculations

¹ Vanderbilt University, Nashville, Tennessee

1207

Objectives: We have used non-uniform rational B-splines (NURBS) models to develop realistic anthropomorphic phantoms for use in nuclear medicine dose assessment, with organ and body masses taken from the reference (50th percentile) values given in ICRP 89. These models have now been scaled to create models of normal weight individuals of different size, i.e. normal body mass index (BMI), to study variations in dose estimates due to changes in normal body stature.

Methods: Using a NURBS scaling software tool, the phantoms were reduced or enlarged to represent 10th, 25th, 75th, and 90th percentile individuals, using anthropometric data from the Centers for Disease Control, National Aeronautics and Space Administration, and the Department of Defense. Scaling of individual organs was based on data from autopsy studies excluding diseased individuals. Other organs were scaled slightly in volume. Organ densities were assumed to be the same for all individuals. Voxelized versions of the phantoms were used in the GEANT4 radiation transport codes for the calculation of photon and electron specific absorbed fractions (SAFs), using typical starting energy values.

Results: Liver and spleen volumes changed substantially for the 25th and 75th percentile individuals but organs such as brain and thyroid changed little. Every organ does not geometrically scale the same percentage during growth, nor do all organs keep exactly the same form. Most organs appear to scale in relation to height while some others scale to BMI.

Conclusions: This set of phantoms will be a practical tool in the assessment of internal dose for normal weight individuals of different body size. This will allow characterization of the variability of SAF values and dose estimates in the nuclear medicine population.

Research Support: This work is supported in part by grant 1R42CA115122-01 from the National Institutes of Health.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Marine, P. Articles by Brill, A. B. PubMed Articles by Marine, P. Articles by Brill, A. B.