Scientists are developing a physics-based virtual model that can simulate a patient’s breathing in real-time. When used in conjunction with existing three-dimensional (3D) models, adding the fourth dimension of time could significantly improve the accuracy and effectiveness of radiation treatment for lung and liver cancers.

Dr. X. George Xu, professor of nuclear and biomedical engineering at Rensselaer Polytechnic Institute (RPI; Troy, NY, USA), and Dr. Suvranu De, an RPI associate professor of mechanical engineering, have formed a multidisciplinary collaboration with clinical colleagues at the Cancer Therapy & Research Center (San Antonio, TX, USA), to develop the 4D Visible Photographic Man (VIP-Man). This virtual model is an extension of Dr. Xu’s ongoing project involving the 3D VIP-Man, which is an advanced computer model that simulates in 3D how radiation affects the organs and tissues in the human body.

“Live patients are not static beings, and 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,” Dr. Xu said. “In order to determine accurate and effective radiation dosages, doctors must consider such issues as the breathing function and air volume change that are affected by several physiological factors over the course of the radiation treatment.”

Real-time simulations could allow clinicians to visualize the small fractions of time when the lungs, liver, kidneys, and eventually the heart, are stationary relative to the external radiation beams. These appropriate moments during the actual therapy mean that clinicians will have more accuracy delivering the radiation to a moving tumor.

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

The fourth dimension of the VIP-Man is not easily accomplished. Currently the researchers are focusing their energy on respiratory function. “Using advanced computational tools, it is possible to simulate lung movement; however, not in real-time,” Dr. De said. “For effective radiation therapy, physics-based real-time performance offers the ultimate solution.”

The major challenge in this project is to develop the algorithms that will make the virtual lungs and adjacent tissues move in real-time according to realistic tissue biomechanical properties, according to Dr. De. Dr. Xu expects that the physics-based 4D VIP-Man will ultimately be used as an even more general anatomic modeling tool for the biomedical community to help patients with respiratory and cardiac diseases.

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