Beam Optics for a Scanned Proton Beam at Loma Linda University Medical Center

摘要

Beam scanning in proton therapy is a medical technique to lower the dose to healthy tissue while irradiating a tumor volume. Scanned proton beams for proton radiation therapy require small beam sizes at the tumor location. In beam scanning, a small beam usually less than 1 cm diameter is swept across the tumor volume with two magnets located several meters upstream of the patient. In general, all proton beams in a therapy facility must be transported from the accelerator to the treatment rooms where the scanning systems are located. This paper addresses the problem of transporting the beam without losses to the patient and achieving a small beam at the tumor location in the patient. The strengths of the beam line quadrupoles were allowed to vary to produce the desired beam sizes along the beam lines. Quadrupole strengths were obtained using the beam simulation program TRANSPORT originally from Stanford Linear Accelerator Center in Palo Alto, CA. An enhanced version of the original program by Accel Soft Inc. in San Diego, CA has been used for these studies. Beam size measurements were used for comparison with TRANSPORT to verify the predictions of TRANSPORT calculations.