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Development of a computational pregnant female phantom and calculation of fetal dose during a photon breast radiotherapy

Vjekoslav Kopacin
Vjekoslav Kopacin
, 
Mladen Kasabasic
Mladen Kasabasic
, 
Dario Faj
Dario Faj
, 
Marijke de Saint Hubert
Marijke de Saint Hubert
, 
Stipe Galic
Stipe Galic
, 
Ana Ivkovic
Ana Ivkovic
, 
Marija Majer
Marija Majer
 y 
Hrvoje Brkic
Hrvoje Brkic
   | 20 oct 2022
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Article Category: Research Article
Publicado en línea: 20 oct 2022
Páginas: 541 - 551
Recibido: 28 jul 2022
Aceptado: 01 ago 2022
DOI: https://doi.org/10.2478/raon-2022-0039
© 2022 Vjekoslav Kopacin, Mladen Kasabasic, Dario Faj, Marijke de Saint Hubert, Stipe Galic, Ana Ivkovic, Marija Majer, Hrvoje Brkic, published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1

Magnified view of the computational phantom’s lower abdomen and pelvis viewed as rendered polygon mesh in the computer 3D modeling software, showing the position of the 18-week-old fetus (in RST position) and placenta in relation to the uterus and the body of the mother. The fetus is shown in light gray colour, the amniotic fluid in transparent blue, the placenta in green, the uterus in transparent purple, and the body of the mother in olive green color.
Magnified view of the computational phantom’s lower abdomen and pelvis viewed as rendered polygon mesh in the computer 3D modeling software, showing the position of the 18-week-old fetus (in RST position) and placenta in relation to the uterus and the body of the mother. The fetus is shown in light gray colour, the amniotic fluid in transparent blue, the placenta in green, the uterus in transparent purple, and the body of the mother in olive green color.

Figure 2

The mesh version of the Tena phantom without skin and soft tissues (A) and with the skin and soft tissues that are shown in transparent light brown color (B). The uterus is shown in transparent purple for a better view of the fetus and its position in space and in relation to other organs.
The mesh version of the Tena phantom without skin and soft tissues (A) and with the skin and soft tissues that are shown in transparent light brown color (B). The uterus is shown in transparent purple for a better view of the fetus and its position in space and in relation to other organs.

Figure 3

Voxelized phantom displayed using MCNP plotter.
Voxelized phantom displayed using MCNP plotter.

Figure 4

Beam arrangements in Eclipse.
Beam arrangements in Eclipse.

Figure 5

Beam Eye View of Field F1, where leafs are represented as transparent rectangles with blue edges. And PTV is colored in green.
Beam Eye View of Field F1, where leafs are represented as transparent rectangles with blue edges. And PTV is colored in green.

Figure 6

Spectra for F1 of the photons coming from the accelerator head and all the photons reaching the fetus (A); Photon spectra in fetus for each field (B).
Spectra for F1 of the photons coming from the accelerator head and all the photons reaching the fetus (A); Photon spectra in fetus for each field (B).

Tena phantom formats and their characteristics

Mesh format DICOM Voxelized
N° vertices1: 2889437 N° faces1: 5777800 Slice thickness: 0.625 mm Distance between slices: 1.867 mm Matrix: 512 x 512 Pixel dimensions: 0.82 mm Grid size: 219 x 148 x 479 N° voxels: 1.55*10-7 Isovoxel size: 0.186 cm

Contribution of each field to the fetal dose. Fetus and breast doses are normalized per source particle, field contribution to the breast dose is obtained from treatment planning system (TPS), and the breast/fetus ratio is calculated from normalized breast and fetus doses

Field Fetus dose per source particle [Gy/SP] 10-19 Breast dose per source particle [Gy/SP] 10-19 Field contribution to breast dose1 Fetus dose normalized to field contribution [Gy/SP] 10-19 Breast dose normalized to field contribution [Gy/SP] 10-19 Ratio fetus / breast dose [mGy/Gy]
F1 1.45 ± 0.12 1000 ± 90 0.437 0.634 ± 0.054 437 ± 37 1.44
F2 1.05 ± 0.09 1070 ± 90 0.378 0.399 ± 0,035 404 ± 36 0.99
F3 1.03 ± 0.08 993 ± 80 0.064 0.066 ± 0,005 63.5 ± 5 1.03
F4 0.270 ± 0.02 1010 ± 80 0.057 0.015 ± 0.001 57.3 ± 4 0.27
F5 0.854 ± 0.07 449 ± 40 0.064 0.055 ± 0,005 28.7 ± 2 1.91
Total 1.169 ± 0.064 992.5 ± 52
Total normalized to prescribed dose 58.9 ± 3.7 mGy 50 Gy*

Relative contribution to the absorbed dose in the fetus (%) originating in the linac or the phantom. The ratio for each field of photons originating in linac or phantom is given in the last row

F1 F2 F3 F4 F5 Overall
Linac (%) 6.0 2.1 0.8 0.3 0.3 9.5
Phantom (%) 37.7 35.7 5.6 5.4 6.1 90.5
Contribution ratio 16.12 5.8 14.3 5.5 4.9

List of the tissues and organs in our developed mesh pregnant female phantom in 2nd trimester (Tena), including volume, mass (calculated as the product of tissue density according to ICRP 89 and segmented organ volume) and surface area

Tissue/organ Volume (cm3) Mass (g) Surface area (cm2)
Adrenal glands 5.1 5.2 40.2
Amniotic fluid 423.4 423.4 381.7
Blood vessels/blood 806.4 854.8 1739.3
Bones, cortex (including
proximal humerus and femoral 2443.4 4691.4 10667.3
heads)
Bone marrow (including proximal humerus and femoral 723.4 724.4 2365.7
heads)
Central nervous system (brain and spinal cord) 1156.3 1214.1 752.4
Colon, content 454.2 472.4 825.5
Colon, wall 287.2 298.7 1914.3
Esophagus, content 4.4 0 42.0
Esophagus, wall 12.2 12.5 123.3
Eyeballs 12.4 13.1 32.9
Fetus, 17 week old 123.0 129.2 200.6
Gall bladder, content 15.5 15.9 42.3
Gall bladder, wall 15.6 16.1 104.1
Kidneys 312.3 327.9 340.4
Liver 1780.4 1869.5 1133.2
Lungs 3937.1 1515.8 2385.4
Myocardium 221.6 232.7 804.1
Pancreas 85.2 89.4 161.3
Parotid glands 24.1 24.9 64.8
Placenta 142.7 145.5 216.8
Soft tissue tissues and (skin) muscles, adipose 36080.41 36802.02 39186.9
Spleen 391.2 406.9 345.0
Stomach, duodenum and small intestine, content 570.3 593.1 1176.1
Stomach, duodenum and small intestine, wall 425.2 442.2 2717.9
Submandibular glands 5.3 5.5 22.0
Thyroid gland 10.0 10.4 3990.0
Upper airways (nasal cavity,
pharynx and larynx) and 136.9 0.1 426.7
trachea/air
Urinary bladder, content 11.1 11.6 38.6
Urinary bladder, wall 21.5 22.2 104.7
Uterus (myometrium) 552.5 580.1 917.6
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