Development of a pregnant woman phantom using polygonal mesh, for dosimetric evaluations

Manuela Ohana Monteiro Cabral,José Wilson Vieira,Viriato Leal Neto,Fernando Roberto De Andrade Lima

doi:10.15392/bjrs.v3i1a.127

Abstract

Due to the embryo/fetus radiosensitivity the accurate estimation of the absorbed dose distribution in the abdominal area is an additional problem caused by the exposure of pregnant women to ionizing radiation in medical applications. This paper reports the construction and insertion of a fetal representation in a female geometry by means of 3D modeling techniques. In order to characterize an ECM the Grupo de Dosimetria Numerica (GDN) is using, mainly, simulators emitting gama sources and voxel phantoms coupled to a MC code. The phantoms are predominantly constructed from stacks of magnetic resonance images (MRI), computed tomography (CT) (obtained from scans of real patients) or from 3D modeling techniques. Due to the difficulty of obtaining medical images of pregnant women, 3D objects in several formats (.obj, .max, .blend, etc.) were acquired for anatomical representation of a non-pregnant adult. To construct a fetal representation, the 3D modeling technique called Poly Modeling (polygon mesh) was used inside of the software Autodesk 3ds Max 2014 (free student version). Information about the radiosensibility of organs included in the abdominal area will be used to fit and use the pregnant phantom in numerical dosimetry. For this, the phantom will be voxelized and the masses of organs of interest will be adjusted according to data provided by International Commission on Radiological Protection (ICRP). Finally, the phantom will be coupled to a MC code creating a MCE that will serve as base for the construction of several other models involving pregnant women submitted to ionizing radiation.

Highlights

The dosimetric evaluation in the abdominal area is of great importance due to the radiosensitivity associated with fetal development
Voxel phantoms constructions made predominantly from magnetic resonance images (MRI), computed tomography (CT) or phantoms mesh from 3D modeling techniques are most-used manner for dosimetric purposes
This paper describes the construction process of a phantom for fetal representation using a minimum number of polygons required for a realistic topology and easy control

Summary

Introduction

The dosimetric evaluation in the abdominal area (after the exposure of pregnant women to ionizing radiation in medical applications) is of great importance due to the radiosensitivity associated with fetal development. Voxel phantoms constructions made predominantly from magnetic resonance images (MRI), computed tomography (CT) (obtained from scans of real patients) or phantoms mesh from 3D modeling techniques are most-used manner for dosimetric purposes. Due to the difficulty of obtaining medical images of pregnant women to manipulate and construct a voxel phantom, the latest generation of computational mesh phantoms can be constructed having images of the structures of interest and practical experience in 3D modeling. Polygon Modeling (or Box-Modeling) is one of the most used techniques for 3D construction [2] by being intuitive and by being implemented in several softwares available In this technique, a solid primitive object (as a cube, for example) serves as the base for creation of any form. Fundamental are the changes in position of the vertices, edges and faces, the use of specific commands into existing modeling softwares and referential images of the object to be created

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Conclusion