Preliminary External and Internal Dosimetry Data from a

Preliminary External and Internal Dosimetry Data from a new set of mother/fetus models JY Zhang, V Taranenko, D Zhang, X. George Xu, Rensselaer Polytechnic Institute, Troy, NY CY Shi 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 2004 From 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 3 D representation from CT Images (external uterine wall). This is a new approach!

Organ Masses Adjusted to ICRP References

From Surfaces to Voxels Re-voxelize at any size (1 mm shown here) Surface Model Adjusted to ICRP reference values Put into MC codes - MCNPX - EGSnrc Voxel Model Geometry in MCNPX code

RPI-P 3, RPI-P 6, and RPI-P 9 Models 3 -month 6 -month 9 -month

Results - Internal photon Specific Absorbed Fractions (RPI-P 9 phantom)

Results - External photons RPI-P 9 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

Acknowledgements • This work is supported by grants 1 R 42 CA 115122 -01 and 5 R 01 CA 116743 -03 from the National Institutes of Health • Drs Mike Stabin and Keith Eckerman provided valuable help on ICRP data analysis Visualization for RPI-P 9 Pregnant Female Model (available at RRMDG. rpi. edu)