Virtual model simulates organ motion and respiratory function

A virtual model that simulates a patient's breathing in real-time is being developed to help improve the accuracy and effectiveness of radiation treatment for lung and liver cancers. The model 4D Visible Photographic Man (4D VIP-Man), in development at the Rensselaer Polytechnic Institute, will add anatomical motion to existing 3D models of the chest and abdomen. The effort is funded by a four-year $2 million grant from the National Library of Medicine.

"A moving organ such as the lung or heart is a main concern in radiation treatment or imaging of tumors that are affected by such organ movement," said X. George Xu, a professor of nuclear and biomedical engineering at Rensselaer Polytechnic and a cocreator of the model. "In order to determine accurate and effective radiation dosages, doctors must consider issues such as changes in the breathing function and air volume that are affected by several physiological factors over the course of the radiation treatment."

Xu and Suvranu De, an associate professor of mechanical engineering at Rensselaer, have formed a multidisciplinary collaboration with clinicians at the Cancer Therapy & Research Center in San Antonio to develop the 4D VIP-Man. This virtual model is an extension of Xu's ongoing 3D VIP-Man project.

Real-time simulations such as the VIP-Man could potentially identify windows in time when the lungs, liver, kidneys, and heart are stationary relative to the external radiation beams. These moments are the best times to deliver radiation to a tumor.

"The 4D VIP-Man will allow doctors and medical physicists to accurately predict and monitor these anatomic changes to provide the most effective treatment possible at any given time," Xu said.

The key challenge for Xu and De is to develop algorithms that will make the virtual lungs and adjacent tissue move in real-time according to biomechanical properties. Xu expects the physics-based 4D VIP-Man will eventually be used as a generally applicable tool for modeling respiratory and cardiac diseases.

In his continuing work on the 3D VIP-Man, Xu intends to create a family of virtual patients, of various ages and sizes, in collaboration with researchers worldwide through the Consortium of Computational Human Phantoms, which he cofounded. He began working on the 3D VIP-Man in 1997, using the original Visible Human Project data set provided by the National Library of Medicine.