Preliminary analysis for integration of spot-scanning proton beam therapy and real-time imaging and gating.
OBJECTIVE
Spot-scanning proton beam therapy (PBT) can create good dose distribution for static targets. However, there exists larger uncertainty for tumors that move due to respiration, bowel gas or other internal circumstances within the patients. We have developed a real-time tumor-tracking radiation therapy (RTRT) system that uses an X-ray linear accelerator gated to the motion of internal fiducial markers introduced in the late 1990s. Relying on more than 10 years of clinical experience and big log data, we established a real-time image gated proton beam therapy system dedicated to spot scanning.


METHODS
Using log data and clinical outcomes derived from the clinical usage of the RTRT system since 1999, we have established a library to be used for in-house simulation for tumor targeting and evaluation. Factors considered to be the dominant causes of the interplay effects related to the spot scanning dedicated proton therapy system are listed and discussed.


CONCLUSIONS
Total facility design, synchrotron operation cycle, and gating windows were listed as the important factors causing the interplay effects contributing to the irradiation time and motion-induced dose error. Fiducial markers that we have developed and used for the RTRT in X-ray therapy were suggested to have the capacity to improve dose distribution. Accumulated internal motion data in the RTRT system enable us to improve the operation and function of a Spot-scanning proton beam therapy (SSPT) system. A real-time-image gated SSPT system can increase accuracy for treating moving tumors. The system will start clinical service in early 2014.
Department of Radiation Oncology, Graduate School of Medicine Hokkaido University, Sapporo, Japan. Electronic address: sshing@med.hokudai.ac.jp.
S
S
Shimizu
Medical Physics, Graduate School of Medicine Hokkaido University, Sapporo, Japan.
T
T
Matsuura
Hitachi, Ltd., Hitachi Research Laboratory, Japan.
M
M
Umezawa
Hitachi, Ltd., Research & Development Group, Japan.
K
K
Hiramoto
Medical Physics, Graduate School of Medicine Hokkaido University, Sapporo, Japan.
N
N
Miyamoto
Division of Quantum Science and Engineering, Graduate School of Engineering Hokkaido University, Sapporo, Japan.
K
K
Umegaki
Department of Radiation Oncology, Graduate School of Medicine Hokkaido University, Sapporo, Japan.
H
H
Shirato
D004867:Equipment Design; D057918:Fiducial Markers; D006801:Humans; D057054:Molecular Imaging; D009068:Movement; D009369:Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D010315:Particle Accelerators; D061766:Proton Therapy / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D011829:Radiation Dosage; D013997:Time Factors
Gated radiotherapy; Image-guided radiation therapy; Organ motion; Spot-scanning proton beam therapy