The UF family of reference hybrid phantoms for computational radiation dosimetry

Abstract

Computational human phantoms are computer models used to obtain dose distributions within the human body exposed to internal or external radiation sources. In addition, they are increasingly used to develop detector efficiencies for in-vivo whole-body counters. Two classes of the computational human phantoms have been widely utilized for dosimetry calculation: stylized and voxel phantoms, that describe human anatomy through mathematical surface equations and 3D voxel matrices, respectively. Stylized phantoms are flexible in that changes to organ position and shape are possible given avoidance of region overlap, while voxel phantoms are typically fixed to a given patient anatomy, yet can be proportionally scaled to match individuals of larger or smaller stature, but of equivalent organ anatomy. Voxel phantoms provide much better anatomical realism as compared to stylized phantoms which are intrinsically limited by mathematical surface equations. To address the drawbacks of these phantoms, hybrid phantoms based on non-uniform rational B-spline (NURBS) surfaces have been introduced wherein anthropomorphic flexibility and anatomic realism are both preserved. Researchers at the University of Florida have introduced a series of hybrid phantoms representing the ICRP Publication 89 reference newborn, 15-year, and adult male and female. In this study, six additional phantoms are added to the UF family of hybrid phantoms – those of the reference 1-year, 5-year, and 10-year child. Head and torso CT images of patients whose ages were close to the targeted ages were obtained under approved protocols. Major organs and tissues were segmented from these images using an image processing software, 3D-DOCTOR™. NURBS and polygon mesh surfaces were then used to model individual organs and tissues after importing the segmented organ models to the 3D NURBS modeling software, Rhinoceros™. The phantoms were matched to four reference datasets: (1) standard anthropometric data, (2) reference organ masses from ICRP Publication 89, (3) reference elemental compositions provided in ICRP 89 as well as ICRU Report 46, and (4) reference data on the alimentary tract organs given in ICRP Publications 89 and 100. Various adjustments and refinements to the organ systems of the previously described newborn, 15-year, and adult phantoms are also presented. The UF series of hybrid phantoms retain the non-uniform scalability of stylized phantoms while maintaining the anatomical realism of patient-specific voxel phantoms with respect to organ shape, depth and inter-organ distance. While the final versions of these phantoms are in a voxelized format for radiation transport simulation, their primary format is given as NURBS and polygon mesh surfaces, thus permitting one to sculpt non-reference phantoms using the reference phantoms as an anatomic template.

Effects of Early-Onset Radiofrequency Electromagnetic Field Exposure (GSM 900 MHz) on Behavior and Memory in Rats

“…Model families of phantoms of various ages and both sexes are now available (Christ et al, 2010a;Lee et al, 2010) and various studies of the SAR distribution in children of different ages, pregnant women and foetuses have been published (Christ et al, 2010b;Dimbylow & Bolch, 2007;Dimbylow, Nagaoka & Xu, 2009;Uusitupa et al, 2010). Further work, including modelling the SAR distribution at different gestational stages, is being pursued in several countries.…”

Personalised Body Counter Calibration Using Anthropometric Parameters

“…Many researchers (Cassola et al 2010;ICRP 2009;Lee et al 2010;Zhang et al 2009) have implemented the 2002 reference man specification by creating computational phantoms with matching body height, body mass, and organ masses. The main application for those phantoms is the calculation of organ absorbed dose fractions for internal and external radiation sources.…”

“…UFH (Lee et al 2007;Lee et al 2010): The models are based on polygon and NURBS meshes approximating segmented computed tomography data. Additional reference anthropometric parameters were derived from a nutrition and health survey and used for the creation.…”

“…These changes are inevitable since phantom developers use different imaging data or stylistic models. The considered phantom series were the ICRP series (ICRP 2009), the RPI series (Zhang et al 2009), the UFPE series (Cassola et al 2010), and the UFH series (Lee et al 2007;Lee et al 2010) each including an adult male and female phantom.…”

Development of a 3D human body library based on polygonal mesh surface for whole body counter set-up calibration

“…And the non-uniform rational basis spline (NURBS) geometry offers a common mathematical framework for implicit and parametric polynomial forms. This mathematical modelling tool is frequently used in computer graphics and animated films industry, thereby showing a method how to overcome some limitations related to the computational voxel phantoms [1][2][3][4]. Although the computational voxel phantoms are anatomically realistic models, most of them are made in supine position and due to the geometry modelling technique the resize of the voxel grids are the only operations allowed which introduces problems of smoothness and continuity when it is necessary to have these models in sitting position.…”