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. This will make it possible for clinics elsewhere to one day duplicate our device.