Construction of realistic hybrid computational fetal phantoms from radiological images in three gestational ages for radiation dosimetry applications

Rasha Makkia,Habib Zaidi,Keith Nelson,Michael Dingfelder

doi:10.1088/1361-6560/ab44f8

Abstract

Radiation exposure and associated radiation risks are major concerns for fetal development for pregnant patients who undergo radiation therapy or diagnostic imaging procedures. In order to accurately estimate the radiation dose to the fetus and assess the uncertainty of fetal position and rotation, three hybrid computational fetus phantoms were constructed using magnetic resonance imaging (MRI) for each fetus model as a starting point to construct a complete anatomically accurate fetus, gravid uterus, and placenta. A total of 27 fetal organs were outlined from radiological images via the Velocity Treatment Planning System. The DICOM-Structure set was imported to Rhinoceros software for further reconstruction of 3D fetus phantom model sets. All fetal organ masses were compared with ICRP-89 reference data. Our fetal model series corresponds to 20, 31, and 35 weeks of pregnancy, thus covering the second and third trimester. Fetal positions and locations were carefully adapted to represent the real fetus locations inside the uterus for each trimester of pregnancy. The new series of hybrid computational fetus models together with pregnant female models can be used in evaluating fetal radiation doses in diagnostic imaging and radiotherapy procedures.

Highlights

Radiation exposure risks for the fetus are a major concern for pregnant patients who undergo radiation therapy or diagnostic imaging procedures (Martin 2011, Xie and Zaidi 2016)
Masses reported in table 1 were obtained from RhinocerosTM with much effort taken to keep non-uniform rational basis spline (NURBS) surfaces or mesh polygon volumes matched with the same original organ volumes that were obtained from the DICOM-structure file when converting to NURBS surfaces for each fetus model
The percentage differences between the derived/calculated fetal organ masses and the average values reported in International Commission of Radiological Protection (ICRP)-89 is shown in table 1.While total fetal masses are within 10%–20% of the average ICRP-89 reference values,individual organs differ up to a factor 2 in size/mass, for example the heart and lungs

Summary

Introduction

Radiation exposure risks for the fetus are a major concern for pregnant patients who undergo radiation therapy or diagnostic imaging procedures (Martin 2011, Xie and Zaidi 2016). The number of patients undergoing radiation therapy has increased because of the noticeable improvement in cancer detection, treatment, and survival of patients. These patients are at higher risk for secondary malignancies due to their radiation exposure (Kry et al 2007). These concerns extend to the fetus if the mother is treated with radiation during pregnancy. The most common invasive cancer types in pregnant women are breast cancer, cervical cancer, lymphoma, malignant melanoma, and thyroid cancer (Rimawi et al 2016, Zagouri et al 2016)

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