A boundary-representation method for designing whole-body radiation dosimetry models: pregnant females at the ends of three gestational periods—RPI-P3, -P6 and -P9

Abstract

Fetuses are extremely radiosensitive and the protection of pregnant females against ionizing radiation is of particular interest in many health and medical physics applications. Existing models of pregnant females relied on simplified anatomical shapes or partial-body images of low resolutions. This paper reviews two general types of solid geometry modeling: constructive solid geometry (CSG) and boundary representation (BREP). It presents in detail a project to adopt the BREP modeling approach to systematically design whole-body radiation dosimetry models: a pregnant female and her fetus at the ends of three gestational periods of 3, 6 and 9 months. Based on previously published CT images of a 7-month pregnant female, the VIP-Man model and mesh organ models, this new set of pregnant female models was constructed using 3D surface modeling technologies instead of voxels. The organ masses were adjusted to agree with the reference data provided by the International Commission on Radiological Protection (ICRP) and previously published papers within 0.5%. The models were then voxelized for the purpose of performing dose calculations in identically implemented EGS4 and MCNPX Monte Carlo codes. The agreements of the fetal doses obtained from these two codes for this set of models were found to be within 2% for the majority of the external photon irradiation geometries of AP, PA, LAT, ROT and ISO at various energies. It is concluded that the so-called RPI-P3, RPI-P6 and RPI-P9 models have been reliably defined for Monte Carlo calculations. The paper also discusses the needs for future research and the possibility for the BREP method to become a major tool in the anatomical modeling for radiation dosimetry.

Katja — the 24th week of virtual pregnancy for dosimetric calculations

“…Several models of pregnant females can be found in the literature, first of all the ORNL-Series of mathematical models by Stabin et al [14] and Chen [2] presenting human anatomy by mathematical means. The voxel models of the pregnant Naomi by Dimbylow [3] and Silvy [1] are constructed for calculations of non ionizing radiation, and RPI-3, RPI-6 and RPI-9 by Xu et al [15] for calculations of ionizing radiation. Dimbylows model is a hybrid one, the mother is a voxel model but the foetus a mathematical phantom basing on a voxelized version of the mathematically modelled foetus of Chen.…”

Fetal and Maternal Absorbed Dose Estimates for Positron-Emitting Molecular Imaging Probes

“…The International Commission on Radiological Protection (ICRP) reference adult female phantom (13) and the Rensselaer Polytechnic Institute (RPI) pregnant female phantom series at 3-, 6-, and 9-mo (RPI-P3, RPI-P6, and RPI-P9) gestation (14) were used in this work to represent embryo/fetus and reference pregnant woman. The voxel-based RPI pregnant female models were generated from the original surface-represented models.…”

Monte Carlo calculations for reporting patient organ doses from interventional radiology

“…It can be divided into three generations during its development: the stylized phantoms are combined with simple geometric elements such as cuboids, cylinders spheres and cones; the voxelized phantoms are constructed by massive of tiny voxels representing anatomical structures; the latest generation computational phantoms are the mesh-based phantoms, which are consisted of Non-Uniform Rational B-Splines (NURBs) or polygonal mesh [26][27][28][29][30][31] . Mesh-based phantoms have powerful abilities of great geometrical deformation and shape adjustment.…”

“…The group of agedependent Chinese adults and adolescences phantoms include males and females with age of new born, 5-year, 10-year, 15-year and adult (named USTC-Adult-Male and USTC-Adult-Female) [32][33][34] , all the anatomical parameters adjusted to agree within 0.5% with the reference people data of China [35] . Other phantoms include pregnant females at 3-month, 6-month and 9-month gestational stages developed from a 30-week pregnant woman CT imaging [27] , reference male and female adults according to ICRP 89 report (named RPI-Adult-Male (RPI-AM) and RPI-Adult-Female (RPI-AF)) [26] , a set of obese males and females with body sizes from normal weight to morbidly obese [30] .…”