New radiation therapy targets tumors more precisely

Software piloted at UI Health Care increases precision of MR-Linac technology 

UI Health Care is the first medical center in North America—and the second in the world—to cross over into the next phase of MR-Linac technology, offering even more precise real-time targeting of soft tissue tumors with radiation therapy.  

MR-Linac technology combines magnetic resonance imaging (MRI) with a linear accelerator to provide real-time tracking of a tumor during radiation therapy. In addition to treating tumors more precisely, the technology also reduces radiation exposure for the patient.  

The new update to MR-Linac technology—known as comprehensive motion management—uses software that automatically turns the radiation beam on and off during treatment to account for any movement of the tumor. 

“The beam will only be enabled when the tumor is in the right position,” says Dan Hyer, PhD, medical physicist and professor in the UI Department of Radiation Oncology. “That allows us to treat with really small margins and not worry that we’re missing the target.”

Traditional devices vs. MR-Linac 

Tumors can move for several reasons. Breathing, for example, can cause a tumor near the diaphragm to move 10 to 20 millimeters during treatment. With traditional devices, care teams must target a larger area to account for tumor movement during treatment. 

MR-Linac, which is used in fewer than 100 places in the world, provides continuous imaging that allows care teams to monitor the position of the tumor throughout the entire treatment. With the addition of comprehensive motion management, doctors can now make sure the beam is off when the target tumor has moved out of position. 

UI Health Care has treated both pediatric patients and adults using comprehensive motion management, and this technology has primarily been focused on tumors in the abdomen and thorax.  

“Tied into that advantage is that you don’t receive an extra radiation dose from MRI,” Hyer says. “If you use traditional computed tomography, there’s an additional radiation dose that you’re receiving.” 

Better imaging using MRI also allows our care teams to provide adaptive therapy.  

“We can use the image we acquire every day before treatment, and we can change the treatment plan to fit the requirements of the day,” Hyer says. “We can provide a personalized plan, which is something you can’t do with a traditional machine.” 

Targeting tumors 

MR-Linac has always been able to monitor tumors, but the software updates from the manufacturer of the machine have introduced the ability to automatically track the target in real time and turn the radiation beam on and off based on the motion of the tumor. 

“We’ve had a number of requests for site visits from premier institutions all around the world,” Hyer says. “From a scientific standpoint, people want to learn about this work we’re doing at the University of Iowa.” 

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