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When people breathe, there¡¯s movement inside their bodies.

Organs, tissues and even cancer patients¡¯ tumors move around all the time,¡± says at MD Anderson. ¡°It¡¯s not unusual for a tumor to shift an inch or slightly more while a patient breathes in and out.¡±

In the past, this movement has confounded doctors¡¯ ability to pinpoint a tumor¡¯s exact location before zapping it with high-energy beams of cancer-killing radiation.

But a new device being tested at MD Anderson promises to overcome that obstacle.

The MR-linac, as it is called, merges a magnetic resonance imaging (MRI) machine and a linear accelerator into a single device. The MRI machine relays high-quality, real-time images of tumors as they¡¯re blasted with radiation beams from the linear accelerator.

MRI machines and linear accelerators have been used in cancer therapy for years. What¡¯s new is the two are now one.

¡°For the first time, this new technology lets us see where the radiation dose is being delivered, as it¡¯s being delivered,¡± Ibbott explains. ¡°The live images keep the radiation directly on target during the treatment.¡±

If a tumor moves out of the targeted radiation area when a patient inhales, the MR-linac automatically turns off the radiation beam. When the patient exhales and the tumor returns to its original position, radiation automatically resumes. This on-off treatment spares healthy tissue and allows doctors to deliver a more powerful dose of radiation.

¡°We used to treat the entire area where the tumor might travel during a normal breathing cycle,¡± he explains. ¡°But with this new technology, radiation is delivered only when the tumor is located where it should be.¡±

Doctors watch treatment sessions on a video monitor. If what they see causes them to tweak the patient¡¯s treatment plan, the MR-linac can refine the target and reconfigure the radiation dose in less than two minutes, all while the patient is on the table. Ibbott calls this ¡°radiation on the fly.¡±

¡°Tailoring radiation to patients¡¯ tumors in real time ¨C it¡¯s the ultimate in personalized medicine,¡± he says.

Magnets and metal

Before the MR-linac¡¯s debut, scientists wouldn¡¯t dare place an MRI machine near a linear accelerator.

¡°That¡¯s because MRI technology uses a powerful magnet to produce high-quality images,¡± Ibbott explains. ¡°The strong magnetic field would pose an obvious safety hazard in the presence of an all-metal linear accelerator, with parts that could fly across the room at a dangerous speed toward the magnet, harming everything in their path. Also, the magnetic field would disturb the operation of the linear accelerator and degrade tumor images.¡±

The MR-linac¡¯s developers created a simple but elegant workaround to bypass this obstacle.

Here¡¯s how Ibbott explains it:

¡°Think of the MRI machine as a hollow paper-towel tube, with a magnetic metal coil wrapping around it. The patient slides inside the tube where imaging takes place.¡±

The MR-linac splits the metal coil in half, creating a gap in the middle where the patient is positioned. Radiation passes through this de-magnetized ¡°safety zone¡± and images are created without distortion.

Leading the way

MD Anderson is the first clinical site in the world to install the MR-linac, other than the University Medical Center in Utrecht, The Netherlands, where it was designed with input from MD Anderson and several other institutions. Today, seven cancer centers worldwide have MR-linacs in place.

The technology has not yet been approved by the Food and Drug Administration. It¡¯s too new, says , who is teaming with Ibbott to conduct a clinical trial of the MR-linac at MD Anderson. 

Data gathered at MD Anderson and other trial sites will provide the machine¡¯s manufacturer, Elekta, with information needed to pursue FDA approval.

Read more about MD Anderson¡¯s role in pursuing FDA approval for the MR-linac in the Annual Report.