Section of Radiation Safety and Quality Assurance

Tetsuo Akimoto, Hidenobu Tachibana, Kenji Hotta, Hiromi Baba, Motoki Kumagai, Kana Motegi, Keiri Akita

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 high-precision RT as intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), respiratory-gating radiation therapy (RGRT), marker-tracking RT, image-guided radiation therapy (IGRT), stereotactic RT, and proton beam therapy (PBT) in cancer treatment.

Our 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 Carlo-based 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 trials are 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.