Proton therapy in Essen, Germany: model patient handling and accurate proton delivery

The next generation of patient throughput optimization is being pursued at the West German Proton Therapy Center (WPE) currently under construction in Essen, Germany. The first patient treatments are scheduled to begin at the end of 2009.

The construction of the new proton therapy center at the University Hospital of Essen in North-Rhine Westphalia, Germany, has begun in July 2007. The facility design plan includes a motorized patient transport system, MRI and CT imaging stations separate from three proton therapy gantry rooms, dedicated Pencil Beam Scanning nozzles in two gantry treatment rooms, and two universal nozzle. “There are two primary goals for this system,” says Jonathan Farr, Ph.D., Chief Medical Physicist at WPE. “Efficiency — you want to treat a lot of patients — and accuracy — you want to maintain the accuracy that proton therapy provides.”

The center, which will be treating its first patients by the end of 2009, focuses on a special feature: improved throughput and patient positioning. Normally, a patient is immobilized and placed onto a patient positioner inside the treatment room. Here, the patient will be prepared outside the room (that is, the patient will be laid and immobilized on a treatment couch in a dedicated preparation line) and the position of the tumor will be registered with a dedicated scanner. Then the patient will be rolled into the treatment room, where he or she will be docked in a smooth and secured way on the patient positioned, so that treatment can begin. In that way, medical staff will save a considerable amount of time that they usually spend inside the room just to prepare the patient, which will considerably increase patient throughput.

The practical efficiency of Essen’s facility plan has resonated with medical physicists at several proton therapy centers currently in development. “It’s being copied by some other centers, which is quite an endorsement,” Farr says. “They like the layout and the automated patient transport system we’re using.” The patient transport system will move patients on Kevlar beds from changing rooms to imaging stations to three gantry treatment rooms, and then return them to their starting point. Wires embedded in the facility floor will guide each bed atop a motorized trolley from one stop to the next along a 200-foot route. “Patients will be loaded onto what we call a ‘universal couch,’” Farr says. “And, they’ll stay on this couch the whole time they go through treatment.” Farr hopes this transport system will improve patient throughput by 20 percent. “It’s not proven,” Farr cautions. “We’ll see if it’s faster than having a patient just walk from station to station. We think it will be, and hope the system will have other advantages, as well.”

The new Essen facility also is capitalizing on the pioneering “out-of-room image guidance” work done at the Paul Scherrer Institute in Switzerland. The idea is that by separating MRI and CT image guidance from the treatment room, radiation oncologists can focus on treating more patients with protons. “Time in the proton therapy room is expensive,” notes Farr. “The majority of time is spent having the patient come in and get set up for beam delivery. If we can take part of the treatment preparation process, such as imaging, out of the gantry room area, we’re not as expensive. “Patient loading, pre-positioning and trolley transport are estimated to reduce the in-treatment room time by about 10 minutes,” Farr continues. “For very complicated cases, this improvement overall in, say, a one-hour total treatment would be about 12 percent. For simple cases such as prostate, the reduction could be as high as 50 percent.”

Essen, Farr says, will be the first proton therapy center to utilize an MRI for image-guided proton beam treatments. “This should lead to lower radiation during imaging,” he says, “which is especially significant for pediatric patients.”