Evaluation of a graphite calorimeter for measuring absorbed dose in heavy-ion beams

The World Congree on Medical Physics and Biomedical Engineering 200

DEVELOPMENT OF 60Co GAMMA-RAY STANDARD FIELD FOR THERAPY-LEVEL DOSIMETER CALIBRATION IN TERMS OF ABSORBED DOSE TO WATER

DEVELOPMENT OF 60Co GAMMA-RAY STANDARD FIELD FOR THERAPY-LEVEL DOSIMETER CALIBRATION IN TERMS OF ABSORBED DOSE TO WATER\nAkifumi Fukumura, Hideyuki Mizuno, Mai Fukahori, Suoh SakataNational Institute of Radiological Sciences (NIRS),Chiba, Japan\nA primary standard for the absorbed dose rate to water in a 60Co gamma-ray field established at National Metrology Institute of Japan (NMIJ) as a primary standard dosimetry laboratory (PSDL) in 2011. Then, a 60Co gamma-ray standard field for therapy-level dosimeter calibration in terms of absorbed dose to water has been developed at National Institute of Radiological Sciences (NIRS) as a secondary standard dosimetry laboratory (SSDL). The field was designed in accordance with IAEA TRS 398.\nThe result of IAEA/WHO TLD SSDL audit with the new field at NIRS demonstrated the good agreement between NIRS stated absorbed dose to water and IAEA TLD measurements within the measurement uncertainty. According to IAEA TECDOC-1585, the relative expanded uncertainty on the calibration factor for therapy-level therapy-level dosimeter in terms of absorbed dose to water (ND,w) with the new field was estimated to 1.1 % (k=2), which is corresponding to an international level such as 1.4% at ADSL in the US and approximately one third of it determined in the air kerma standard field previously existing at NIRS. \nThe new field has been used for determination of ND,w for radiotherapy facilities in Japan since the beginning of October in 2012. At the same time Japan Society of Medical Physics (JSMP) updated its code of practice for dosimetry in external radiotherapy. The dissemination of traceability of calibration factor determined in the new field is expected to diminish the uncertainty of dose delivered to patients significantly.12th Asia-Oceania Congress of Medical Physics (12th AOCMP

A calibration system of therapy-level dosimeter in terms of absorbed dose to water by ANTM

A calibration system of therapy-level dosimeter in terms of absorbed dose to water by ANTMThe 7th Korea-Japan Joint Meeting on Medical Physic

Recent results of a postal dose audit for radiotherapy machine in Japan with non-reference condition

Purpose In Japan, postal dose audits have been performed on the radiation therapy units using a radiophotoluminescent glass dosimeter (RGD) since 2007. In 2010, the audit for the non-reference condition including field size change or wedge insertion was initiated. This study summarizes the latest results of non-reference condition.Methods Through these 4 years, 458 beams have been measured for different field size from 5 x 5 cm2 to 25 x 25 cm2 and 301 beams have been measured for different wedge angle from 15 to 60 degrees.Results For the beams with the field size change, the mean differences of measured from stated dose at each field size, 5 x 5 (n = 197), 15 x 15 (n = 55), 20 x 20 (n = 173), and 25 x 25 (n =33) cm2, were -0.3%, 0.3%, 0.4%, and 0.2% respectively. The standard deviations of the distribution at each field size were 1.0%, 1.0%, 1.2%, and 1.5% respectively. For the wedged beam irradiation, the mean of the differences of measured from stated dose with each wedge angles, 15° (n = 112), 30° (n = 102), 45° (n = 45), and 60° (n = 42), were 0.1%, 0.1%, 0.1%, and 0.3% respectively. The standard deviations of the distribution at each wedged angle were 1.0%, 1.3%, 1.2%, and 1.3% respectively. Conclusion The postal dose audit using RGD to non-reference condition has been successfully performed. The mean differences of measured from stated dose were within 0.5% for every field size and wedge angle.The 7th Korea-Japan Joint Meeting on Medical Physic

Results of Dose Audit of Radiation Therapy Facilities in East-Asian Countries

Dose audit was conducted to radiation therapy facilities in East-Asian Countries. This activity was done through the framework of the Forum for Nuclear Cooperation in Asia (FNCA). A radiophotoluminescent glass dosimeter was used as the detector. The dose of reference condition was measured for 20 beams of 7 facilities from 4 countries, China, Korea, Indonesia and Vietnam. The deviation between the calculated and measured dose was analyzed and the standard deviation was 1.9% (k=1). One beam exceeded the tolerance level, which is over 5%. The difference was finally fixed through the contact with local staff. This event shows the importance of external audits in radiation therapy.The 5th Korea - Japan Joint Meeting on Medical Physics（第９６回日本医学物理学会学術大会

Feasibility study of glass dosimeter postal dosimetry audit of high-energy radiotherapy photon beams

INTRODUCTION: \nThe characteristics of a glass dosimeter were investigated for its potential use as a tool for postal dose audits. Reproducibility, energy dependence, field size and depth dependence were compared to those of a thermoluminescence dosimeter (TLD), which has been the major tool for postal dose audits worldwide.\nMATERIALS AND METHODS: \nA glass dosimeter, GD-302M (Asahi Techno Glass Co.) and a TLD, TLD-100 chip (Harshaw Co.) were irradiated with gamma-rays from a (60)Co unit and X-rays from a medical linear accelerator (4, 6, 10 and 20 MV).\nRESULTS: \nThe dosimetric characteristics of the glass dosimeter were almost equivalent to those of the TLD, in terms of utility for dosimetry under the reference condition, which is a 10 x 10 cm(2) field and 10 cm depth. Because of its reduced fading, compared to the TLD, and easy quality control with the ID number, the glass dosimeter proved to be a suitable tool for postal dose audits. Then, we conducted postal dose surveys of over 100 facilities and got good agreement, with a standard deviation of about 1.3%.\nCONCLUSIONS: \nBased on this study, postal dose audits throughout Japan will be carried out using a glass dosimeter