54 A. Chaikh et al.: Radioprotection 2025, 60( 1), 50 – 56
Table 1. Chemical composition, in percentage(%), of the VeroWhite resin determined by CHONS method.
Values % |
N |
C |
H |
O |
Mean |
2.89 |
65.51 |
7.95 |
23.28 |
Standard deviation |
0.02 |
0.13 |
0.05 |
0.15 |
Fig. 4.( a) Calculated total attenuation coefficients of the VeroWhite resin( 2.89 % N, 65,51 % C, 7,95 % H and 23,65 % O) compared to water( H 2 O), as a function of photon energy.( b) measured linear attenuation coefficients as a function of RW3 and VeroWhite resin thicknesses for a 6 MV beam.
3.4 Measured linear and mass attenuation coefficients
The values of measured linear attenuation coefficients as a function of RW3 plates and VeroWhite resin thicknesses are presented in Figure 4b. The average relative difference in attenuation coefficients obtained as a function of RW3 and VeroWhite resin thicknesses is about 12 %( 12,8 % when disregarding the 1 cm thickness point measurement).
The mass attenuation coefficients are calculated by dividing by the density of the two materials: 1.19 g / cm 3 and 1.045 g / cm 3 for the resin and RW3 respectively. The average relative difference obtained between the two materials for the mass attenuation coefficient is 1 %(-0.1% when disregarding the 1 cm thickness point measurement).
4 Discussion
The technique used in this study to design and print the desired phantoms allowed for the printing of 3D models with precise geometrical accuracy and smooth opaque surfaces. As a result, the 3D printed structures were placed in contact with the surface of the ATOM ® phantom, and the complementary volumes fit together easily. An irregular surface of a printed belly can lead to an air gap with the surface of the phantom affecting the dose measurements. The CT scanner acquisition parameters play a significant role in achieving a good spatial resolution for the 3D printed model to reduce these amounts of air gap and ensure smooth parts that fit well together. The use of a CT scan with a spatial resolution of 0.625 mm was adapted. Moreover, a high-quality 3D printer capable of precise geometric printing, like the one used in this study, is necessary.
The 3D-printed bellies allow for the simulation of two different trimesters of pregnancy in a woman whose morphology is equivalent to that of the ATOM phantom. The definition of these pregnancy bellies was based on gynecological data( fundal height). The fetal dose can thus be easily measured by inserting a FARMER-type ionization chamber into the designated holes according to the stage of pregnancy. These phantoms were developed to assess the influence of certain beam parameters on the fetal dose and are suitable for parametric studies. Using this phantom is well suited for this purpose but not necessarily for managing a real pregnant woman. Indeed, an important factor influencing fetal dose is the distance between the treated volume and the fetus. Assessing the impact of this distance on fetal dose assessment is therefore essential to validate the use of a phantom of fixed size as developed, based on the size of the CIRS female phantom, for a real patient.
The chemical and physical characteristics measured in this study enable a better evaluation of dosimetric equivalences for its use in creating phantoms in the medical field, whether in radiotherapy or radiology. The skeletal measured density of the VeroWhite resin was 1.190 þ / �0.001 g / cm 3 whereas the manufacturer indicates a density of( 1.17-1.18 g / cm 3) 6. An explanation could be that the density provided by the manufacturer considers the air in the volume attributed to the mass, unlike our measurement. Nevertheless, the differ-
6 https:// www. sculpteo. com / fr / materiaux / materiau-resine-polyjet / materiau-verowhite /.