December 20, 2007 - Researchers from Rensselaer Polytechnic Institute have developed a new set of modeling tools that could enable safer, more accurate and more effective radiation therapy and nuclear medicine imaging procedures for pregnant women.
Instead of employing the conventional constructive solid geometry (CSG) tools, George Xu, professor of nuclear and biomedical engineering, and his team turned to boundary representations (BREP) tools. CSG models are based on building and connecting simple shapes such as spheres, cones, and cylinders to create a larger structure. BREP is more flexible and features a more robust toolbox for manipulating the surface of model components and is widely used in the manufacturing industry for computer-aided design , and in the entertainment industry to create computer-animated models for movies and video games, Xu said. As it turns out, BREP software is also highly effective for creating medical phantoms consisting of complex organs.
Using this new set of tools, Xu and his team created three 3D models of pregnant females at various gestational stages: three months, six months, and nine months. The team built the models of the expecting mother and fetus organ by organ, relying on computer-generated mesh models, as well as supplanting the model with data from rare CT scan images of a pregnant patient. The images were taken around 2004 in an upstate New York hospital, in a situation where both the woman and her physician were unaware she was pregnant. The existence of such scans was publicized, and Xu contacted the physician to obtain copies of the scans. Xu said BREP turned out to be extremely effective for modeling the complex topology of human organs, and he expects the practice to catch on.
Physicians use advanced computer simulations to determine the correct dose of radiation to administer to patients. These computer simulations are based on sophisticated virtual models of the human body. About 30 of these models, sometimes called “phantoms,” have been developed worldwide. The data needed to build such models requires extensive X-rays and computed tomography scans. Since pregnant patients are prohibited from undergoing X-rays or other imaging procedures, there has never been enough data to create an accurate phantom of a pregnant woman.
With the models complete, Xu and his team will share their data with other researchers investigating the same topic and will likely be about one year before the models are verified and accepted by the medical community, and then integrated into computer software as a new standard for determining and administering radiation therapy to expecting mothers.
Co-authors on the paper include Rensselaer nuclear engineering and engineering physics graduate student Juying Zhang, and postdoctoral research associate Valery Tarenenko. Chengyu Shi, of the Cancer Therapy and Research Center in San Antonio, Texas, is also listed as a co-author.
For more information: www.rpi.edu
January 30, 2026 
