LBL Research Review August 1994

THANKS IN LARGE PART to the initiative and creativity of a group of LBL researchers, a project to transfer LBL's eye cancer treatment program from the Bevatron to the University of California at Davis has been completed. The UC Davis clinic, dedicated strictly to the treatment of uveal melanoma (eye cancer), opened this May. The facility is expected to treat about 40 people a year.

The LBL effort involved a multidisciplinary team, including radiation oncologist Joe Castro, physicist Tim Renner, electronic engineer Mark Nyman, software engineer R.P. Singh, and mechanical technician Mario Cepeda. In essence, the team replicated the program at UC Davis using the 70 MeV Crocker Nuclear Laboratory Cyclotron.

Treating an eye tumor with the Crocker Lab's proton beam can save not only lives but unlike conventional surgery, the eye itself. Unlike x-rays, proton beams can avoid damaging the healthy tissue surrounding a tumor. Protons deposit almost all of their radiation dose near the end of their tracks, where they stop. Using beam delivery systems developed at LBL, the Davis proton beam is custom-shaped for each patient, depositing its energy in a space that coincides with the three-dimensional shape of the tumor.

Treatment requires locking in place the patient's head and fixing its position so that the beam strikes the target tumor with absolute precision. That's where the unique skills of technician Cepeda came in. His contribution was to build a device to precisely position the patient during treatment.

The device, a high-tech chair that adjusts in many directions, can cost upwards of $250,000. Since limited funds existed to design a device, Castro and Renner turned to Cepeda.

"At times," says Renner, "we forget that there are very creative people throughout the Lab. Mario took it upon himself to design and build this chair. From an engineering standpoint he had no model to work from, just his nine years experience working with us in the particle radiotherapy program. He built the entire patient positioner out of scavenged parts and pieces of aluminum."

Cepeda said he hand-milled the majority of the approximately 200 parts, purchasing only one part.

By necessity, the device is an object of absolute precision. Tumors in the eye are extraordinarily tiny, typically one centimeter or less in diameter, and can be located next to the optic nerve. Sight is lost if, during treatment, the beam hits the optic nerve. So, the patient positioner must be able to move and hold the patient's head with a wiggle room of less than one millimeter.

For a patient, sitting in the chair at the business end of a proton beam can be a scary experience. Cepeda did what he could to minimize the trauma. The chair was designed, engineered, and assembled based upon his hand sketches, which he repeatedly modified and refined. To improve this process, Cepeda spent $6,000 of his own money to purchase a home computer and Computer Assisted Design (CAD) software.

"I'm transferring my sketches of the patient positioner to CAD," he says. "This will make it possible for clinics elsewhere to one day duplicate our device."

LBL's own radiotherapy program now becomes part of medical history. But thanks to the LBL team, what was learned will live on in the patients who will be treated at Davis.

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