Half of all cancer patients receive some kind of radiation during their treatment, the most common being external radiation therapy. But radiation can kill cancer cells and normal cells, so it’s important that it’s directed at precisely the right spot.
That’s easier said than done, as radiologists want to make sure they zap all of the tumor, but don’t want to get too much of the healthy tissue around it. And it poses a specific challenge for tumors located in the abdomen, where organs move naturally as patients breathe during treatment.
That was the problem Stanford University mechanical engineering and bioengineering student Jeff Schlosser wanted to address when he began his Ph.D. project. What he created as a result was a method that uses 3-D ultrasound and robotics to enable radiation therapy to continually adapt to anatomy motion.
Now Schlosser and his two Ph.D. advisers at Stanford, Dr. Dimitre Hristov, an assistant professor of radiation oncology, and Dr. Kenneth Salisbury, a professor of computer science and surgery, have spun out the technology into a company called SoniTrack Systems.
SoniTrack’s offering is an ultrasound device that’s designed to be held by a robotic arm against a patient’s torso as radiation is being delivered. It tracks soft tissue movement in real-time and communicates that movement to the linear accelerator that’s delivering the radiation. That way, radiation can be halted when the tumor shifts outside of the treatment margin.
The idea is that this would not only result in less damage to surrounding tissue, but it would also shrink the necessary treatment margin around the tumor, so that more precise and concentrated radiation treatments could be delivered with less risk of damaging healthy tissue.
An existing technique for delivering high-precision radiotherapy, called intensity-modulated radiation therapy, allows for a radiation dose to conform more precisely to the 3-D shape of the tumor, but it’s used primarily in treating prostate, head and neck, and central nervous system cancers. Initially, Schlosser said, SoniTrack’s technology will be applied to the treatment of liver cancer, which affects about 30,000 new Americans each year.
First- and second-generation prototypes of the device have already been tested in healthy volunteers, he said, and the most recent iteration of the robotics technology and the treatment planning software are set to begin an early stage clinical trial at a Bay Area hospital later this year.
[Photo courtesy of Jeff Schlosser]