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Matzavinos

Anastasios Matzavinos, ISU Mathematics

NEWS RELEASE
College of Liberal Arts and Sciences, Iowa State University
www.las.iastate.edu

8-17-09

Contacts:
Anastasios Matzavinos, Mathematics, (515) 294-1752 (tasos@iastate.edu)
Steve Jones, Liberal Arts & Sciences Communications, (515) 294-0461 (jones@iastate.edu)

ISU mathematician part of research team that’s first to publish quantified model to improve a plastic surgery procedure

AMES, Iowa –Mathematics is playing a role in efforts by plastic surgeons to ensure success of live tissue transfers from one part of a person’s body to another.

In the first published quantitative model of tissue transfer, physicians and mathematicians have teamed to ensure tissue segments chosen for transfer will receive enough blood and oxygen to survive.

Anastasios Matzavinos, assistant professor of mathematics at Iowa State University, said research, which uses differential equations, has shown mathematics can take the guesswork out of such transfers. Matzavinos and mathematicians and plastic surgeons from Ohio State University have developed mathematical models of the blood supply and oxygen in tissue segments. The modeling could reduce failures in reconstructive surgery.

Matzavinos is one of the authors of the study published in the July 21 edition of the Proceedings of the National Academy of Sciences. The research is supported by the National Science Foundation.

Tissue transfers are often used to rebuild body parts damaged by disease or injury, such as the reconstruction of a woman’s breast following cancer surgery. In this example, a plastic surgeon will cut away a segment of the patient's tissue, often from the lower abdominal area, and reattach it to restore her breast.

The removed tissue, called the flap, is fed by perforator vessels, a vein and artery that travel through muscle to support skin and fat. Matzavinos said surgeons believe the vessels must be at least 1.5 millimeters in diameter to provide oxygen flow to sustain the flap.

In earlier procedures, physicians removed the skin and underlying muscle. The more-invasive procedure resulted in abdominal immobility and loss of strength. Surgeons now routinely take only the fat tissue and the vessel. However, because the muscle is no longer transferred, the diameter of the vessel must be the correct size to provide enough blood for the flap to live.

“Right now there is no medical protocol for this,” said Matzavinos. “Surgeons only use their experience and trial and error.

“If we know more about the relationship between the size of the perforated blood vessels and the size of the tissue flap to be transferred, the surgeries will be more reliable.”

If the initial blood oxygen levels in the transferred tissue are not at least 15 percent of the corresponding levels in blood, according to the study, the tissue farthest from the vessels will begin to die. This results in additional surgery and sometimes the entire procedure must be redone.
           
Matzavinos said measuring the blood flow through small vessels and the thousands of tiny capillaries is the challenge. “We don’t know the exact vascular structure of the tissue,” he noted. Researchers, however, developed a way to average the oxygen concentration of the capillaries.
           
The mathematical model uses three values: the average oxygen concentration in the capillaries, the rate of exchange from vessels to tissue and the pressure under which the blood is flowing through the vessels.

Five differential equations provide a range between the flap size and the needed diameter of the vessels.

“This is a new predictive tool that can provide consistent results for physicians,” Matzavinos said.
           
The mathematical model is still under development and will need to be tested. However, Matzavinos is confident it can someday be part of an imaging and software package that will provide surgeons with reliable data on the likelihood of survival of transferred tissue.

The paper’s other authors are all from Ohio State: Michael Miller, professor of surgery and director of the Division of Plastic Surgery; Avner Friedman, Distinguished University Professor and former director of the Mathematical Biosciences Institute (MBI); Chiu-Yen Kao, MBI and Department of Mathematics; J. Edward Green, a postdoctoral fellow at the MBI; and Alok Sutradhar, a postdoctoral fellow in plastic surgery

Matzavinos is a former visiting faculty member at Ohio State.

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