Learning as they go along

Because Mevion's system has the accelerator attached to the gantry, DOTmed asked if the superconductive qualities therein could be disrupted by gantry rotation. "We've had a real quench and a false detected quench, but it's only happened twice since we started trials two years ago," said Klein, "I don't think that's different than the frequency that the other systems have had, so I don't think the rotation is a culprit."


In the early months of installation there was a process of learning how to keep the cooling system consistent throughout gantry rotation. "It has to have some flexibility to allow for rotation and maintain cooling," said Klein. They redesigned the turrets to resolve the problem, which was important because when the system shuts down it can take a couple of days to get back in business.

"It's an art to bringing up a magnet current alongside its cooling. It's a play between the two and requires the right balance," explained Klein. "If you bring up the current too fast without the cooling you'll have a melting magnet, if you cool down too much you may not get the current going." Klein described it as a dance between power and cooling.

The next nine months, and beyond

Now that the S. Lee Kling Center for Proton Therapy is plowing along at full workload, they are seeing about 21 patients per day. Klein said some therapies' prescriptions require as few as five treatments or as many as 40, but most patients receive therapy 25 to 33 times. As of today, their 85th patient has started treatment, which puts them on schedule to surpass their goal of 100 patients in the first year.

In terms of workload, about half of the patients they see are either pediatric cases or receiving central nervous system (CNS) treatment. Only about 6 percent of the proton therapy they do is on prostate cases. When asked why that is, Klein said they have had great success treating prostate with intensity modulated radiation therapy, and because proton treatment availability is limited, they prioritize the cases where the benefits are most clearly illustrated — that means CNS and pediatrics.

While recent reports indicate there are 14 proton therapy centers in the U.S., Klein would like to see that number jump to 20 or 25. "Oklahoma City has the same basic population as St. Louis," said Klein, "We have one machine and will probably add another in the next two years, which should be about right for us. Meanwhile, Oklahoma City has six rooms planned, which is too many." Klein feels that more attention should be given to managing the distribution of proton centers so that they benefit the most patients.

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