Preliminary External and Internal Dosimetry Preliminary External and Internal Dosimetry Data from a new set of mother/fetus modelsData from a new set of mother/fetus models

JY Zhang, V Taranenko, D Zhang, X. George Xu, JY Zhang, V Taranenko, D Zhang, X. George Xu, Rensselaer Polytechnic Institute, Troy, NYRensselaer Polytechnic Institute, Troy, NY

CY Shi CY Shi Cancer Therapy and Research Center, San Antonio, TX Cancer Therapy and Research Center, San Antonio, TX

Project Motivation (Pregnant Female Models)

• High radio-sensitivity for the fetus

• Needs for accurate dosimetry– Occupational (if the pregnancy is declared)– Nuclear medicine – Radiation treatment of pregnant patients (increasing!)– Air traveling– non-ionizing radiation (RF etc)

• Models difficult to develop– Twice as many tissues and organs– 3-month, 6-month and 9-month gestational periods– Medical images are rare

Project Goals

1) Development a new set of models of pregnant mother and fetus at the end of 3-, 6- and 9-month gestational periods

2) Compile organ dose parameters for external and internal irradiations

Existing Pregnant Female Models

Stylized models- Stabin 1995

- Chen 2004From partial-body CT image set- Shi and Xu (2004)

They are un-realistic and in-complete

Method: Flow Chart of Pregnant Female Model Development

Model Extraction of 3D representation from CT Images (external uterine wall).

This is a new approach!

Mass (g) RPI

Organ

RPI-3DModel

RPI-voxel-1mm Reference data

RPI-voxel-1mm vs reference data (%)

Reference density (g/cm3)

Volume for RPI-voxel-1mm (cm3)

Fixed volume organs Brain 1,299.49 1,299.46 1,300.00 0.0 1.04 1,249.48 Eyeballs 14.63 14.62 14.60 0.1 1.03 14.25 Eye lens 0.40 0.40 0.40 0.1 1.10 0.36 Thyroid 17.00 17.00 17.00 0.0 1.05 16.19 Trachea 7.99 8.00 8.00 0.0 1.03 7.77 Thymus 20.00 20.00 20.00 0.0 1.03 19.51 Lungs 950.34 950.16 950.00 0.0 0.25 3,800.63 Heart wall 250.15 250.15 250.00 0.1 1.03 242.86 Heart cont. 369.96 369.98 370.00 0.0 1.06 349.04 Esophagus 35.00 34.95 35.00 -0.1 1.03 33.93 Stomach wall 139.56 139.53 140.00 -0.3 1.04 134.16 Stomach cont. 230.67 230.66 230.00 0.3 1.04 221.79 Liver 1,399.81 1,399.71 1,400.00 0.0 1.05 1,333.05 Gallbladder wall 8.00 7.98 8.00 -0.2 1.03 7.75 Gallbladder cont. 48.19 48.20 48.00 0.4 1.03 46.79 Pancreas 119.68 119.66 120.00 -0.3 1.05 113.96 Spleen 129.58 129.66 130.00 -0.3 1.06 122.32 Kidneys 275.04 275.07 275.00 0.0 1.05 261.97 Adrenals 13.00 13.03 13.00 0.2 1.02 12.78 SI wall and cont. N/A 880.00 880.00 0.0 1.04 846.15 LI wall 682.24 360.00 360.00 0.0 1.04 346.15 LI cont. N/A 319.74 320.00 -0.1 1.04 307.44 Ovaries 11.00 10.99 11.00 -0.1 1.05 10.47 Bladder wall 40.11 40.09 40.00 0.2 1.04 38.55 Bladder cont. 129.37 129.43 130.00 -0.4 1.04 124.46 Skeleton 7,862.62 7,798.26 7,800.00 0.0 1.30 5,998.66 Skin N/A 2,300.00 2,300.00 0.0 1.10 varies Variable volume organs Uterine wall 3 m 270.11 270.32 270.10 0.1 1.05 257.45 6 m 549.94 549.99 548.90 0.2 the same 523.80 9 m 1,046.85 1,045.28 1,050.00 -0.4 the same 995.51 Uterine cont. 3 m 859.61 859.16 859.20 0.0 1.03 834.14 6 m 3,657.42 3,657.06 3,657.80 0.0 the same 3,550.54 9 m 4,108.67 4,121.65 4,140.00 -0.4 the same 4,001.60 Placenta 3 m 47.50 47.43 47.50 -0.1 1.04 46.18 6 m 319.26 319.28 319.20 0.0 the same 308.48 9 m 650.00 649.88 650.00 0.0 the same 624.88 Fetal soft tiss. 3 m 70.92 71.30 71.30 0.0 74.17 6 m 902.21 902.59 902.50 0.0 0.97 931.57 9 m 2,754.45 2,747.98 2,760.00 -0.4 1.00 2,756.81 Fetal skeleton 3 m N/A N/A N/A N/A N/A N/A 6 m 78.38 77.92 78.00 -0.1 1.22 63.87 9 m 371.00 370.41 370.00a 0.1 the same 303.61 Fetal brain 3 m 13.60 13.60 13.60 0.0 1.03 13.36 6 m 133.93 133.92 134.10 -0.1 the same 130.28 9 m 369.95 370.04 370.00 0.0 the same 359.26 Breasts 3 m 569.52 569.94 569.00 0.2 1.05 542.80

Organ Masses Adjusted to ICRP References

From Surfaces to Voxels

Surface ModelAdjusted to ICRP reference values Voxel Model Geometry in

MCNPX code

Re-voxelize at any size(1mm shown here)

Put into MC codes- MCNPX- EGSnrc

RPI-P3, RPI-P6, and RPI-P9 Models

9-month6-month3-month

Results - Internal photon Specific Absorbed Fractions

(RPI-P9 phantom)

Results - External photons

RPI-P9 phantom; total fetal dose

Conclusion• A series of pregnant female and fetus phantoms

have been developed• Organ masses are adjusted according to ICRP

reference values• External photon, electron, neutron and proton

sources have been studied

• Internal photon and electron sources have been studied

• ICRP is hoped to adopt the RPI-P series as standard pregnant-female models

Visualization for RPI-P9 Pregnant Female Model

(available at RRMDG.rpi.edu)

Acknowledgements

• This work is supported by grants 1R42CA115122-01 and 5R01CA116743-03 from the National Institutes of Health• Drs Mike Stabin and Keith Eckerman provided valuable help on

ICRP data analysis