放射治療與腫瘤學Therapeut Radiol Oncol 2008; 15(1): 21-34
21
Quality assurance schedule and Practical exPerience
with helical tomotheraPy
Pei-Ju Chao
1, Tsair-Fwu Lee
2, Stephen Wan Leung
1,3, Ying-Chen Chang
1,
Tze-Liang Huang
1, and Chung-Chou Juan
4,*
Department of Radiation Oncology1, Kaohsiung Yuan’s General Hospital
Chang Gung Memorial Hospital- Kaohsiung Medical Center2, Chang Gung University, College of Medicine
Department of Radiological Technology3, Central Taiwan University of Science and Technology
Commission on Radiological Protection4, Kaohsiung Yuan’s General Hospital
Purpose : We present a quality assurance (QA) schedule for the Hi-Art Helical Tomo-Therapy unit and share our QA practical experience with this state-of-the-art machine. According to the Ionizing Radiation Protection Act (Article. 17, item 3), the regulation of medical exposure QA in Taiwan has to include daily, monthly, and annual items in the schedule for every treatment machine in a radiation oncology department. The Hi-Art Helical TomoTherapy unit was developed at the University of Wisconsin-Madison in 2003. We installed a new system at Yuan’s General Hospital to take the lead in South-Taiwan in April 2006. In this study, we present the QA schedule that is performed in our department, which follows the principles of AAPM TG-40 but contains some novel com-ponents, reflecting the differences between the Hi-Art device and conventional linear accelerators.
Materials and Methods : We compared the efficiency of the daily, monthly, and annual QA programs in our department with Hi-Art Helical TomoTherapy unit and an Elekta-Precise linear accelerator with a standard QA schedule. We followed the principles of AAPM TG-40. For tomotherapy, the QA program included a series of measurements that were recorded in a specially fabricated, cylindrically symmetric Virtual Water phantom. This was designed specifically for commissioning the Helical TomoTherapy unit and QA. The phantom is 30cm in diameter, 18cm long, and is divided into two halves, such that film may be placed between them.
To perform the measurements of the dosimetry parameters and correction factors, three EXRADIN-A1SL ion chambers and a Standard Imaging-TomoEletrometer were used for the Helical TomoTherapy unit, and a 0.6CC PTW TM30013 Farmer chamber with PTW T0008 Eletrometer was used for the Elekta-Precise linear accelerator. For the beam quality measurements, the dedicated TomoTherapy electrometer measurement system (TEMS) along with a two-dimensional radiation beam analyzer (TomoScanner) and a PTW-Freiburg MP3-S therapy beam analyzer water phantom system were performed the scanning for the beam symmetrical profiles assessment for the corresponding machine respectively.
Results : The lengths of time required for daily QA program was almost the same for
Received: 2007, 2, 16. Accepted: 2007, 5, 24.
Address reprint request to: Dr. Stephen Wan Leung., Department of Radiation Oncology, Yuan’s General Hospital, 162 Cheng Kung 1st Road, Kaohsiung, Taiwan (80211) R.O.C.
