Annual Report 2018
Section of Radiation Safety and Quality Assurance
Tetsuo Akimoto, Hidenobu Tachibana, Kenji Hotta, Horomi Baba, Kana Moteg, Ryo Takahashi
Introduction
Radiation therapy (RT) technologies have improved recently and will continue to progress. However, while advanced technology has provided higher accuracy and precision in RT, it has introduced more complex situations and difficulties in performing the treatment adequately. RT errors can occur at several time points from planning through treatment. The accuracy and precision of dose delivery in RT is important because there is evidence that a 7-10% change in the dose to the target volume may result in a significant change in tumor control probability. "Quality assurance in RT" is for all procedures that ensure consistency of the medical prescription, and safe fulfillment of that prescription, as regards the dose to the target volume, together with the minimal dose to normal tissue, minimal exposure of personnel and adequate patient monitoring aimed at determining the end result of the treatment.
The primary aim of the Section of Radiation Safety and Quality Assurance is to develop quality assurance programs for photon and proton therapy machines as well as to check that quality requirements in photon and proton therapy products are met and to adjust and correct performance if the requirements are found not to have been met. The second aim is to install and establish advanced technologies in clinical practices in the Department of Radiation Oncology. Other goals are to develop highprecision RT as intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), respiratory-gating radiation therapy (RGRT), marker-tracking RT, imageguided radiation therapy (IGRT), stereotactic RT, and proton beam therapy (PBT) in cancer treatment.
The Team and What We Do
At present, the staff of the Section of Radiation Safety and Quality Assurance consists of one radiation oncologist, three medical physicists, and one radiological technologist. We have more than 1,000 new patients for photon and proton therapy every year. Our section is responsible for four linear accelerators, two CT simulators, and four different treatment planning systems in photon/electron therapy. In proton therapy, one accelerator, two treatment units, and one planning system are managed.
Quality assurance programs have been established for photon and proton therapy by the medical physicists. The daily, monthly and annual programs are performed by the medical physicists and radiological technologists. In addition, the medical physicists perform RT planning for IMRT/VMAT in prostate and head and neck sites, stereotactic RT in the liver and lungs, and proton therapy in the head and neck, esophagus, lung, liver, prostate, and infants. The medical physicists support conventional RT planning and also check the quality and safety for all treatment plans.
Research activities
In the Section of Radiation Safety and Quality Assurance, the following research activities are on-going:
1) Design and development of new proton beam irradiation system
2) Design and development of monitor unit calculation for proton therapy
3) Design and development of a Monte Carlobased dose calculation algorithm for proton therapy
4) Design and development of a CT-based image guided and adaptive proton therapy system
5) Design and development of four-dimensional planning for motion synchronized dose delivery for photon therapy
6) Design and development of CT-pulmonary ventilation imaging
7) Design and development of quality assurance system for gated RT
8) Multi-institutional study of independent MU/Dose verification for conventional, stereotactic RT, IMRT, VMAT as well as for Vero, CyberKnife, and Tomotherapy in photon therapy
Clinical trials
The following multi-institutional clinical trial is ongoing:
1) Establishment of safety for RT planning of photon therapy
Education
We established an on-the-job training (OJT) program for quality assurance programs for a photon linear accelerator and over 100 medical physicists and radiological technologists have taken the educational program. We held a meeting for independent MU/dose verification and over 180 medical physicists and radiological technologists participated in the meeting. We trained graduated students from the University of Tsukuba and Komazawa University for a quality assurance program in photon therapy.
Future prospects
We maintain the quality of photon/electron and proton therapy machines and also establish new technologies to improve patient outcomes. In addition, we will work on RT as well as radiology including the establishment of a quality assurance program for diagnostic instruments and management of radioactive materials.
List of papers published in 2018
Journal
1. Motegi K, Tachibana H, Motegi A, Hotta K, Baba H, Akimoto T. Usefulness of hybrid deformable image registration algorithms in prostate radiation therapy. J Appl Clin Med Phys, 20:229-236, 2019
2. Yamashita M, Takahashi R, Kokubo M, Takayama K, Tanabe H, Sueoka M, Ishii M, Tachibana H. A feasibility study of independent verification of dose calculation for Vero4DRT using a Clarkson-based algorithm. Med Dosim, 44:20-25, 2019
3. Tachibana H, Uchida Y, Miyakawa R, Yamashita M, Sato A, Kito S, Maruyama D, Noda S, Kojima T, Fukuma H, Shirata R, Okamoto H, Nakamura M, Takada Y, Nagata H, Hayashi N, Takahashi R, Kawai D, Itano M. Multi-institutional comparison of secondary check of treatment planning using computer-based independent dose calculation for non-C-arm linear accelerators. Phys Med, 56:58-65, 2018
4. Moriya S, Tachibana H, Hotta K, Nakamura N, Sakae T, Akimoto T. Range optimization for target and organs at risk in dynamic adaptive passive scattering proton beam therapy - A proof of concept. Phys Med, 56:66-73, 2018
5. Tachibana H, Motegi K, Moriya S. Impact of shoulder deformation on volumetric modulated arc therapy doses for head and neck cancer. Phys Med, 53:118-128, 2018
6. Takahashi R, Kamima T, Itano M, Yamazaki T, Ishibashi S, Higuchi Y, Shimizu H, Yamamoto T, Yamashita M, Baba H, Sugawara Y, Sato A, Nishiyama S, Kawai D, Miyaoka S, Tachibana H. A multi-institutional study of secondary check of treatment planning using Clarkson-based dose calculation for three-dimensional radiotherapy. Phys Med, 49:19-27, 2018
7. Miyakawa S, Tachibana H, Moriya S, Kurosawa T, Nishio T, Sato M. Design and development of a nonrigid phantom for the quantitative evaluation of DIR-based mapping of simulated pulmonary ventilation. Med Phys, 2018
8. Miyakawa S, Tachibana H, Moriya S, Kurosawa T, Nishio T. Evaluation of deformation parameters for deformable image registration-based ventilation imaging using an air-ventilating non-rigid phantom. Phys Med, 50:20-25, 2018
9. Jinno S, Tachibana H, Moriya S, Mizuno N, Takahashi R, Kamima T, Ishibashi S, Sato M. A multi-institutional study of independent calculation verification in inhomogeneous media using a simple and effective method of heterogeneity correction integrated with the Clarkson method. J Radiat Res, 59:490-500, 2018
10. Kamima T, Baba H, Takahashi R, Yamashita M, Sugawara Y, Kawai D, Yamamoto T, Satou A, Tachibana H. Multi-institutional comparison of computer-based independent dose calculation for intensity modulated radiation therapy and volumetric modulated arc therapy. Phys Med, 45:72-81, 2018