Hybrid Computational Phantoms Representing the Reference Adult Male and Adult Female

Abstract

Currently, two classes of the computational phantoms have been developed for dosimetry calculation: (1) stylized (or mathematical) and (2) voxel (or tomographic) phantoms describing human anatomy through mathematical surface equations and 3D voxel matrices, respectively. Mathematical surface equations in stylized phantoms are flexible but the resulting anatomy is not as realistic. Voxel phantoms display far better anatomical realism, but they are limited in terms of their ability to alter organ shape, position, and depth, as well as body posture. A new class of computational phantoms - called hybrid phantoms - takes advantage of the best features of stylized and voxel phantoms - flexibility and anatomical realism, respectively. In the current study, hybrid computational phantoms representing the adult male and female reference anatomy and anthropometry are presented. These phantoms serve as the starting framework for creating patient or worker sculpted whole-body phantoms for retrospective dose reconstruction. Contours of major organs and tissues were converted or segmented from computed tomography images of a 36-year Korean volunteer and a 25-year U.S. female patient, respectively, with supplemental high-resolution CT images for the cranium. Polygon mesh models for the major organs and tissues were reconstructed and imported into Rhinoceros™ for non-uniform rational B-spline (NURBS) surface modeling. The resulting NURBS/polygon mesh models representing body contour and internal anatomy were matched to anthropometric data and reference organ mass data provided by Centers for Disease Control and Prevention (CDC) and International Commission on Radiation Protection (ICRP), respectively. Finally, two hybrid adult male and female phantoms were completed where a total of 8 anthropometric data categories were matched to standard values within 4% and organ volumes matched to ICRP data within 1% with the exception of total skin. The hybrid phantoms were voxelized from the NURBS phantoms at resolutions of 0.158 × 0.158 × 0.158 cm3 and 0.126 × 0.126 × 0.126 cm3 for the male and female, respectively. To highlight the flexibility of the hybrid phantoms, graphical displays are given of (1) underweight and overweight adult male phantoms, (2) a sitting position for the adult female phantom, and (3) extraction and higher-resolution voxelization of the small intestine for localized dosimetry of mucosal and stem cell layers. These phantoms are used to model radioactively contaminated individuals and to then assess time-dependent detector count rate thresholds corresponding to 50, 250, and 500 mSv effective dose, as might be needed during in-field radiological triage by first responders or first receivers.

Internal photon and electron dosimetry of the newborn patient—a hybrid computational phantom study

“…The reference lymphatic node mass of the newborn phantom, 10 g, was calculated by downscaling the reference mass from the adult value, 210 g, which was derived from the masses of the lymphatic nodes in extrathoracic and thoracic regions (ICRP 1994) and the total number of lymphatic node sites. The average size of a single lymphatic node, 0.24 cm in radius, was downscaled by the width of the phantom from the value of the UF reference adult phantom (Hurtado et al in press). An in-house MATLAB code, Lymphatic Node Generator, was used to create the lymphatic nodes within the voxelized newborn phantoms node-by-node until the total reference mass of the lymphatic nodes were matched.…”

RADAR Reference Adult, Pediatric, and Pregnant Female Phantom Series for Internal and External Dosimetry

“…Similar discrepancies between the stylized and voxelized models were reported using the VIP-Man model, which is based on the Visible Human Project cadaver cross-sectional anatomic images (7,8). Hurtado et al (9) reported on hybrid realistic computational phantoms for adults and used them in retrospective dosimetry analyses for contaminated radiation workers. Many others have developed individual realistic phantoms of adults (10,11), children (12), and pregnant women (13,14), using various technologies, as summarized by Xu and Eckerman (5).…”

Quantitative impact of changes in marrow cellularity, skeletal size, and bone mineral density on active marrow dosimetry based upon a reference model

“…Target tissues included both the active marrow and shallow marrow, defined as the surrogate tissue regions for marrow stem cells and osteoprogenitor cells, respectively. Bone macrostructural models were taken directly from the individual bones within the University of Florida (UF) hybrid computational phantom of the reference adult female . In the present study, the bone models of the lower ribs, L3 lumbar vertebra, and parietal bone of the cranium are taken from the O'Reilly model of the reference adult female .…”