For the first time, ultrasound is being used in animal models -- to treat cancer by disrupting tumor blood vessels. Researchers at the University of Pennsylvania School of Medicine completed a study in mice in which they used ultrasound both to see a tumor's blood perfusion and then to treat it with a continuous wave of low-level ultrasound. After three minutes of treatment at an intensity similar to what is used in physiotherapy ultrasound (about 2.5 watts), researchers observed that the tumors had little or no blood supply.
"We used an ultrasound intensity higher than that used for imaging, but much lower than the high intensities used to ablate tissue. And we saw that this new use had a profound effect on shutting down the blood flow to the tumor and reducing the growth of the tumor in mice," said Chandra Sehgal, PhD, Director of Ultrasound Research in the Department of Radiology at Penn and the study's principal investigator.
"We wanted to study this use of ultrasound because we observed that some of these newly formed vessels created by tumors are very weak in nature, and if you turn on low-intensity ultrasound vibrations you can disrupt the blood flow through these vessels," explained Andrew Wood, DVSc, PhD, a co-investigator of the study and based in the University of Pennsylvania School of Veterinary Medicine.
Sehgal adds, "This approach is in keeping with the latest study of cancer treatment utilizing antiangiogenic and antivascular therapies, in which we look for ways to stop the growth of the vessels supplying blood and nutrition to the tumors, rather than develop methods to kill the tumor cells themselves."
For years, ultrasound has been used for clinical imaging and for therapeutic action in physical therapy. But now, Sehgal explains, "These results are extremely encouraging. They raise the possibility that, in the future, treatments with ultrasound either alone or with chemotherapeutic and antivascular agents could be used to treat cancers."
The results of this study were published in the October 2005 issue of "Ultrasound in Medicine and Biology." You can access it on-line at: www.sciencedirect.com (search for the UMB journal and then access Volume 31 -- October 2005, article 15 "The Antivascular Action of Physiotherapy Ultrasound on Murine Tumors").
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