Application of a radiophotoluminescent glass dosimeter to nonreference condition dosimetry in the postal dose audit system Hideyuki Mizuno, Akifumi Fukumura, Mai Fukahori, Suoh Sakata, Wataru Yamashita, Nobuhiro Takase, Kaori Yajima, Tetsurou Katayose, Kyoko Abe-Sakama, Yohsuke Kusano, Munefumi Shimbo, and Tatsuaki Kanai Citation: Medical Physics 41, 112104 (2014); doi: 10.1118/1.4898596 View online: http://dx.doi.org/10.1118/1.4898596 View Table of Contents: http://scitation.aip.org/content/aapm/journal/medphys/41/11?ver=pdfcov Published by the American Association of Physicists in Medicine Articles you may be interested in The response of a radiophotoluminescent glass dosimeter in megavoltage photon and electron beams Med. Phys. 41, 122102 (2014); 10.1118/1.4901639 Characterization of a novel 2D array dosimeter for patient-specific quality assurance with volumetric arc therapy Med. Phys. 40, 071731 (2013); 10.1118/1.4812415 Evaluation of Al 2 O 3 : C optically stimulated luminescence (OSL) dosimeters for passive dosimetry of highenergy photon and electron beams in radiotherapy Med. Phys. 35, 260 (2008); 10.1118/1.2816106 A radiophotoluminescent glass plate system for medium-sized field dosimetry Rev. Sci. Instrum. 76, 106104 (2005); 10.1063/1.2074587 Application of a radiophotoluminescent glass plate dosimeter for small field dosimetry Med. Phys. 32, 1548 (2005); 10.1118/1.1925187

Application of a radiophotoluminescent glass dosimeter to nonreference condition dosimetry in the postal dose audit system Hideyuki Mizuno,a) Akifumi Fukumura, and Mai Fukahori National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba-shi 263-8555, Japan

Suoh Sakata, Wataru Yamashita, and Nobuhiro Takase Association for Nuclear Technology in Medicine, 7-16, Nihonbashikodenmacho, Chuou-ku, Tokyo 103-0001, Japan

Kaori Yajima Toho University Omori Medical Center, 6-11-1 Omori-Nishi, Ota-ku, Tokyo 143-8541, Japan

Tetsurou Katayose Chiba Cancer Center, 666-2 Nitona-Cho, Chuoh-ku, Chiba-shi, Chiba 260-8717, Japan

Kyoko Abe-Sakama Gunma University, Heavy Ion Medical Research Center, 4-2, Aramaki-machi, Maebashi City, Gunma 371-8510, Japan

Yohsuke Kusano Kanagawa Cancer Center, 1-1-2 Nakao, Asahi-ku, Yokohama-shi, Kanagawa 241-8515, Japan

Munefumi Shimbo Saitama Medical Center, 1981, Kamoda, Kawagoe-shi, Saitama 350-8550, Japan

Tatsuaki Kanai Gunma University, Heavy Ion Medical Research Center, 4-2, Aramaki-machi, Maebashi City, Gunma 371-8510, Japan

(Received 11 May 2014; revised 30 September 2014; accepted for publication 5 October 2014; published 29 October 2014) Purpose: The purpose of this study was to obtain a set of correction factors of the radiophotoluminescent glass dosimeter (RGD) output for field size changes and wedge insertions. Methods: Several linear accelerators were used for irradiation of the RGDs. The field sizes were changed from 5 × 5 cm to 25 × 25 cm for 4, 6, 10, and 15 MV x-ray beams. The wedge angles were 15◦, 30◦, 45◦, and 60◦. In addition to physical wedge irradiation, nonphysical (dynamic/virtual) wedge irradiations were performed. Results: The obtained data were fitted with a single line for each energy, and correction factors were determined. Compared with ionization chamber outputs, the RGD outputs gradually increased with increasing field size, because of the higher RGD response to scattered low-energy photons. The output increase was about 1% per 10 cm increase in field size, with a slight difference dependent on the beam energy. For both physical and nonphysical wedged beam irradiation, there were no systematic trends in the RGD outputs, such as monotonic increase or decrease depending on the wedge angle change if the authors consider the uncertainty, which is approximately 0.6% for each set of measured points. Therefore, no correction factor was needed for all inserted wedges. Based on this work, postal dose audits using RGDs for the nonreference condition were initiated in 2010. The postal dose audit results between 2010 and 2012 were analyzed. The mean difference between the measured and stated doses was within 0.5% for all fields with field sizes between 5 × 5 cm and 25 × 25 cm and with wedge angles from 15◦ to 60◦. The standard deviations (SDs) of the difference distribution were within the estimated uncertainty (1SD) except for the 25 × 25 cm field size data, which were not reliable because of poor statistics (n = 16). Conclusions: A set of RGD output correction factors was determined for field size changes and wedge insertions. The results obtained from recent postal dose audits were analyzed, and the mean differences between the measured and stated doses were within 0.5% for every field size and wedge angle. The SDs of the distribution were within the estimated uncertainty, except for one condition that was not reliable because of poor statistics. C 2014 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4898596] Key words: radiophotoluminescent glass dosimeter, dose audit, radiation therapy, quality assurance, nonreference condition

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© 2014 Am. Assoc. Phys. Med.

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1. INTRODUCTION In Japan, postal dose audits have been performed on radiation therapy units using a radiophotoluminescent glass dosimeter (RGD), since 2007.1 By the end of fiscal year 2012, the reference condition, which is a 10 × 10 cm field with 10 cm depth, was verified on 570 linear accelerator (Linac) beams. However, the reference condition audit is only the first level of the postal dose audit defined by Izewska et al.2,3 We aim to expand the postal dose audit to the second level, which includes nonreference conditions with field size changes and wedge insertions. This secondary audit is more efficient in preventing radiation accidents because some of the accidents were related to incorrect output factors or incorrect wedge factors. The International Atomic Energy Agency (IAEA)/World Health Organization (WHO) and Imaging and Radiation Oncology Core (IROC) thermoluminescent dosimetry (TLD) postal dose audit group also developed a methodology for performing TLD audits under nonreference conditions.3,4 As discussed in our previously published study,1 the RGD output increases as the field size increases because of changes in the x-ray energy spectrum. The mean x-ray energy decreases in large fields because of the increase in scattered photons within the field. Because of the high RGD response to low-energy photons (around several hundred kiloelectronvolts), a correction should be applied for field size changes. Araki et al.,5,6 Rah et al.,7 and Perks et al.8 successfully applied the RGD to small-field beam dosimetry. However, their works were limited to the comparison of measurement outputs between the RGD and another detector such as a diode detector or film, and lacked systematic correction data. To determine a correction factor that is valid for a practical audit routine, we performed comprehensive dose measurements with RGD for x-ray beam energies from 4 to 15 MV. Furthermore, because the effect on the RGD output by the insertion of a wedge had not been previously reported, we studied the RGD output response for wedge insertion by measurements for both physical and nonphysical (virtual/dynamic) wedges. Based on this work, the postal dose audit for the nonreference condition was initiated in 2010. In this study, we show systematic correction factors for both field change and wedge insertion, and analyze the first three years of dose audit data.

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the reading is very small. The principles and practice of the signal reading are described in detail in previously published papers.5,6 The reproducibility was 0.8% in standard deviation (SD). Depending on the irradiated beam energy, a small energy correction, such as 1.007 for 4 MV and 1.025 for 15 MV, was applied to the reading.1 2.B. Methodology of postal dose audit

Three RGDs and a water-equivalent solid phantom (Tough Water Phantom, KYOTO KAGAKU CO., Kyoto, Japan) were sent to radiotherapy facilities, where the RGDs were irradiated with a 1-Gy dose in either the reference or nonreference condition of the x-ray beam. The size of the phantom was 30 × 30 cm, and the central region was gouged to hold the glass dosimeters (Fig. 1). The three RGD elements were set perpendicular to the beam axis in 1-cm intervals and were set at the 10-cm depth in the phantom on the isocenter plane. For each irradiation, the averaged output of the three elements was used as the output of the beam. The RGD output was calibrated by six control elements, which were irradiated with a dose of 1 Gy by a 60Co gamma-ray beam at the National Institute of Radiological Sciences (NIRS) (Secondary Standard Dosimetry Laboratory). The control elements were used not only to translate the RGD output to the absorbed dose to water but also to calibrate the sensitivity of the reader. The absorbed dose to water was calculated from the measured RGD outputs with the following equation:   3 elements(q) (X i × Ii )/3 × Eq × Pq × Dose60Co   Dqref = . (1) 6 elements(60Co) (X i × Ii )/6 Here, X i and Ii are the raw output value and the sensitivity correction factor (derived by uniform irradiation using 60Co gamma rays) of the glass element whose ID number is i, respectively. Eq (such as 1.007 for 4 MV and 1.025 for 15 MV x-ray) and Pq (such as 1.005 for 4 MV and 1.010 for 15 MV x-ray) are the energy correction factor and phantom correction

2. MATERIALS AND METHODS 2.A. RGD

The RGD (DOSE ACE, Asahi Glass Co., Tokyo, Japan) is a silver-activated phosphate glass with the following weight composition: 11.0% Na, 31.55% P, 51.16% O, 6.12% Al, and 0.17% Ag.9 The RGD is 1.5 mm in diameter and 12 mm in length. The readout area for the RGD is 1 mm in diameter from its central axis and 6 mm in length for normal dose mode (up to 10 Gy). The longitudinal center is offset from the geometrical center for about 1.8 mm because of the design of reading magazine. An ID number is engraved for each element. The output precision is improved by performing sequential readings. The depletion of the signal due to Medical Physics, Vol. 41, No. 11, November 2014

F. 1. Experimental setup for changing field sizes and wedged beams. The dosimeters were placed at a depth of 10 cm on the isocenter plane. The geometrical center of the middle element corresponded to the isocenter.

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factor of beam quality q, respectively. These correction factors were determined in a previous study.1 The energy correction factor is the response correction due to the energy spectrum change normalized to the energy of 60Co gamma rays. The phantom correction factor is the ratio of measured output in the water to the measured output in the phantom. Finally, Dose60Co is the dose measured by ionization chamber (IC) irradiated by 60 Co gamma rays immediately before the irradiation of the control elements using the same setup in the solid phantom. A detailed description for each correction factor can be found in previous work.1 To apply the audit to the nonreference condition, we modified Eq. (1) as follows: Dqnon-ref   3 elements(q) (X i × Ii )/3 × Eq × Pq × FA ×W × Dose60Co   , = 6 elements(60Co) (X i × Ii )/6 (2) where FA is the field size correction factor and W is the wedged beam correction factor. Specifically, FA is the correction factor of the RGD output for a square field with side length A, normalized to the reference field size of 10 × 10 cm, and W is the correction factor of the RGD output for wedge insertion. 2.C. Irradiation by the Linac beam

Several Linacs were used for the irradiation of RGDs. For the changing field size study, the following Linacs were used: Clinac21EX (Varian Medical Systems, Palo Alto, CA), Synergy (Elekta AB, Stockholm, Sweden), EXL-15DP (Varian Medical Systems, Palo Alto, CA), and Vero4DRT (Mitsubishi Heavy Industries, Tokyo, Japan). The field sizes were changed from 5 × 5 cm to 25 × 25 cm for 4, 6, 10, and 15 MV x-ray beams. For the wedged field irradiation, PRIMUS (Siemens, Erlangen, Germany) and ClinaciX (VARIAN Medical Systems, Palo Alto, CA) were used in addition to the above Linacs to study all popular Linac models in Japan. The wedge angles were 15◦, 30◦, 45◦, and 60◦. In addition to the physical wedge irradiation, nonphysical (dynamic/virtual) wedge irradiations were also performed. The irradiation conditions were the same as the routine postal dose audit methodology described in Sec. 2.B, which is 1 Gy at a 10-cm depth. Before the irradiation of RGDs, IC measurements (PTW TN30013) were performed using the same geometry. The output differences between the RGD and the IC were analyzed to derive the correction factor for the RGD. 2.D. Implementation to the postal dose audit

The postal dose audit for nonreference conditions was initiated in FY 2010 using the correction factors obtained in this work. For field size changes, four conditions such as 5 × 5 cm, 15 × 15 cm, 20 × 20 cm, and 25 × 25 cm can be selected by a facility in addition to the reference condition. For the wedged beam, four conditions such as 15◦, 30◦, 45◦, and 60◦ can be selected. We analyzed results collected from FY 2010 to 2012. Medical Physics, Vol. 41, No. 11, November 2014

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T I. Uncertainty budget of the RGD readings for dose audit.

Quantity source of uncertainty X i ; raw output value (for three elements of the user beam irradiation) Ii ; sensitivity correction factor (for three elements of the user beam irradiation) E q ; energy correction factor Pq ; phantom correction factor Dose60Co; output of the ionization chamber X i ; raw output value (for six elements of the 60Co gamma-ray irradiation) Ii ; sensitivity correction factor (for six elements of the 60Co gamma-ray irradiation) Other component (uncertainty for the phantom thickness ambiguity used for irradiation) F A; field size correction factor W ; wedged beam correction factor Dq ref ; combined uncertainty of the RGD dose (reference condition) Dq nonref ; combined uncertainty of the RGD dose (beam with field size is not 10 × 10 cm) Dq nonref ; combined uncertainty of the RGD dose (wedged beam)

Uncertainty type

Uncertainty (1SD)

Type A

0.33%

Type B Type B Type B

0.87% 0.12% 0.52%

Type A

0.23%

Type B

0.17%

Type B Type B

0.87% 1.15%

Combined

1.11%

Combined

1.41%

Combined

1.60%

2.E. Uncertainty budget

The uncertainty budget of Dqref and Dqnonref was estimated according to each component of Eqs. (1) and (2). The uncertainty of X i and Ii was derived from the statistical analysis of numerical element outputs. The uncertainty of Eq and Pq was derived by considering the maximum correction factors necessary to cover all beam energy regions. The uncertainty of Dose60Co was also derived by considering the maximum values of each parameter to obtain the absolute dose, including ionization chamber readings and pressure/temperature measurements. The uncertainty of FA and W was derived in the same way as Eq and Pq , using the results of this study. These results are summarized in Table I.

3. RESULTS AND DISCUSSION 3.A. Field size correction factor

Figures 2(a)–2(d) show the difference in the RGD output from the IC output as a function of the field size side length. The RGD output was derived using Eq. (1). The inverse of this difference can be directly used as a correction factor

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for the RGD output. The output differences were studied at four beam energies: 4, 6, 10, and 15 MV. The uncertainty of each measured point was 0.6% (k = 1). This value was partially derived using the uncertainty budget shown in Table I, excluding unnecessary components such as Eq , Pq , and part of Dose60Co. Some points were the average of several measurements with the same conditions. As shown in Fig. 2, the RGD outputs gradually increase as the field size increases compared with IC outputs. As mentioned previously, RGD has a higher response to low-energy photons. Therefore, as the field size increases, low-energy scattered radiation increases, and the RGD outputs increase. Similar responses were observed with all Linacs. We applied a linear fit to all measured points, as shown in Fig. 2. At 4 and 15 MV, the fitted line did not cross 0.0% at the reference condition (10-cm side length). Ideally, the correction factor for the reference condition should be 1.0. These discrepancies may occur due to RGD reading fluctuations or systematic errors in the energy correction factor of the RGD, especially for the 15-MV beam. Though the energy correction factor should be updated in the future, this effect is independent from the field size correction factor. Considering the uncertainty of each measured point (0.6%) and the uncertainty of the energy correction factor (0.87%), the fitted line was adjusted to be 1.0 at field size 10 × 10 cm to eliminate the above discrepancies. Finally, the correction factor FA was fixed as follows: 4 MV : FA = 1/(1 + 1.278 × 10−3(A− 10)), 6 MV : FA = 1/(1 + 8.616 × 10−4(A− 10)), 10 MV : FA = 1/(1 + 6.333 × 10−4(A− 10)), 15 MV : FA = 1/(1 + 7.932 × 10−4(A− 10)). Here, A is the side length of the square field (cm). 3.B. Wedged beam correction factor

Figures 3(a)–3(d) show the difference of the output of the RGD from the IC as a function of wedge angles. The output differences were studied at four beam energies: 4, 6, 10, and 15 MV. The uncertainty of each measured point was normally 0.6% (k = 1). Some points were the average of several measurements with the same conditions. For both physical and nonphysical wedge data, though there was some variability, we cannot determine a clear trend in the data such as a monotonic increase or decrease depending on the wedge angle change. The energy spectrum may have been considerably affected at the surface of the phantom, but this may not affect the results at a 10-cm depth. A correction factor for wedge insertion is not necessary if we add the maximum deviation of 1.15% to the uncertainty budget. 3.C. Comparison with optically stimulated luminescence dosimeters (OSLD) F. 2. The percentage difference of the RGD output from the IC output with field size change for (a) 4 MV, (b) 6 MV, (c) 10 MV, and (d) 15 MV beams. The uncertainty of each measured point was 0.6% (k = 1). The data were categorized by Linac manufacturer. Medical Physics, Vol. 41, No. 11, November 2014

Because OSLD have been widely implemented10–13 and have similar characteristics to RGDs, it is worthwhile to compare the benefits and disadvantages between the two kinds of dosimeters. The OSLDs also contain aluminum, which is a

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high-atomic-number material; therefore, OSLDs are expected to have similar characteristics to RGDs with respect to a high response to low-energy x-rays. Viamonte et al.14 studied the field size dependence from 5 × 5 cm to 22 × 22 cm of OSLD using a 60Co beam and found no systematic trend in the effect of field size. However, from their published data, a slight linear tendency could be observed at the same level as this study. As their error bars in the graph were ±2%–5% larger than the error in this study, they may have overlooked the trend. For wedged beam irradiation, unfortunately, we could not find any published results using OSLD. The other characteristics such as reproducibility, linearity, and energy dependence seemed to be comparable with other reports.10–16 However, RGD has some advantages compared with OSLD such as a reduced fading effect [negligible for RGD, but about 2.5% in 30 days for OSLD (Ref. 15)] and a reduced depletion effect [about 1.5% in 100 readings for RGD, but about 3% in 100 readings for OSLD (Ref. 11)]. Moreover, RGD can accept more accumulated dose than OSLD without changing its response. Aguirre et al.16 reported that 10 Gy was identified as the limit of cumulative dose for OSLD. For the RGD, from our experience, the signal was reproducible up to 25 Gy or more. 3.D. Recent data with applying the correction factors

From FY 2010 to 2012, dose audits for 309 beams for the field size change and 185 beams for the wedged beam

F. 3. The percentage difference of the RGD output from the IC output with wedge insertion for (a) 4 MV, (b) 6 MV, (c) 10 MV, and (d) 15 MV. The uncertainty of each measured point was normally 0.6% (k = 1). The data were categorized by Linac manufacturer. Medical Physics, Vol. 41, No. 11, November 2014

F. 4. The results of the audit performed from FY 2010 to 2012 for (a) the field size change (n = 309) and (b) wedge insertion (n = 185).

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were performed with RGDs using the factors obtained in this study. The results are shown in Figs. 4(a) and 4(b). For the beams with field size changes, the mean differences between the measured and stated dose at the field sizes of 5 × 5 cm (n = 129), 15 × 15 cm (n = 35), 20 × 20 cm (n = 129), and 25 × 25 cm (n = 16) were −0.3%, 0.1%, 0.2%, and −0.4%, respectively. The standard deviations of the distribution at each field size were 1.0%, 1.0%, 1.1%, and 1.7%, respectively. Except for the 25 × 25 cm field size data, all standard deviations were within the estimated standard deviation from Sec. 2.E (1.41%). The data for the 25 × 25 cm field size are not reliable due to poor statistics. For wedged beam irradiation, the mean of the differences between the measured and stated dose at the wedge angles of 15◦ (n = 78), 30◦ (n = 62), 45◦ (n = 26), and 60◦ (n = 19) was 0.0%, 0.0%, −0.1%, and 0.5%, respectively. The standard deviations of the distribution at each wedged angle were 1.0%, 1.3%, 1.0%, and 1.5%, respectively. All standard deviations were within the estimated standard deviation from Sec. 2.E (1.60%). Though some conditions require additional measurements to improve the statistics, the applied correction factor for both field size changes and wedge insertions was considered to be valid because this audit defines the tolerance level to be within 5%.

4. CONCLUSION This study describes a set of correction factors of the RGD output for the field size changes and wedge insertions. These factors were derived using actual measurement data. For field size changes, the RGD outputs slightly increased compared with IC outputs as the field size increased due to the higher response to low-energy scattered x-rays. The correction factors for field size changes were obtained using the inverse of the measured data fitting. For the wedged beams, there was no clear data trend with the wedge angle for both physical and nonphysical wedges. To consider the variations in the measured data, we applied a larger uncertainty to the wedged beam. Based on this work, the postal dose audit for the nonreference condition was initiated in 2010. The data between 2010 and 2012 were analyzed, and the mean differences of measured from stated dose were within 0.5% for every field size and wedge angle. The standard deviation of the distribution is also within the estimated uncertainty, except for the 25 × 25 cm field size condition, which is not reliable due to poor statistics.

ACKNOWLEDGMENTS The authors would like to acknowledge the staff of the National Institute of Radiological Sciences (Hospital), Jyuntendo University Nerima Hospital, National Cancer Center Hospital East, Kimitsu Chuo Hospital, Hamamatsu Medical Center,

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Nagano Red Cross Hospital, Okayama Central Hospital, Nihonkai General Hospital (Yamagata-Sakata Hospital organization), and Obihiro Kosei Hospital for their support in obtaining the data for the correction factors. a)Author

to whom correspondence should be addressed. Electronic mail: [email protected] 1H. Mizuno, T. Kanai, Y. Kusano, S. Ko, M. Ono, A. Fukumura, K. Abe, K. Nishizawa, M. Shimbo, S. Sakata, S. Ishikura, and H. Ikeda, “Feasibility study of glass dosimeter postal dosimetry audit of high-energy radiotherapy photon beams,” Radiother. Oncol. 86, 258–263 (2008). 2J. Izewska, H. Svensson, and G. Ibbott, “Worldwide quality assurance networks for radiotherapy dosimetry,” in Proceedings of International Symposium Standards and Codes of Practice in Medical Radiation Dosimetry, IAEA-CN-96/76 (IAEA, Vienna, 2002), pp. 139–156. 3J. Izewska, D. Georg, P. Bera, D. Thwaites, M. Arib, M. Saravi, K. Sergieva, K. Li, F. G. Yip, A. K. Mahant, and W. Bulski, “A methodology for TLD postal dosimetry audit of high-energy radiotherapy photon beams in nonreference conditions,” Radiother. Oncol. 84, 67–74 (2007). 4G. S. Ibbott, D. S. Followill, H. A. Molineu, J. R. Lowenstein, P. E. Alvarez, and J. E. Roll, “Challenges in credentialing institutions and participants in advanced technology multi-institutional clinical trials,” Int. J. Radiat. Oncol., Biol., Phys. 71(Suppl. 1), S71–S75 (2008). 5F. Araki, T. Ikegami, T. Ishidoya, and H. D. Kubo, “Measurements of Gamma-Knife helmet output factors using a radiophotoluminescent glass rod dosimeter and a diode detector,” Med. Phys. 30, 1976–1981 (2003). 6F. Araki, N. Moribe, T. Shimonobou, and Y. Yamashita, “Dosimetric properties of radiophotoluminescent glass rod detector in high-energy photon beams from a linear accelerator and Cyber-Knife,” Med. Phys. 31, 1980– 1986 (2004). 7J. E. Rah, D. O. Shin, J. S. Jang, M. C. Kim, S. C. Yoon, and T. S. Suh, “Application of a glass rod detector for the output factor measurement in the CyberKnife,” Appl. Radiat. Isot. 66, 1980–1985 (2003). 8J. Perks, M. Gao, V. Smith, S. Skubic, and S. Goetsch, “Glass rod detectors for small field, stereotactic radiosurgery dosimetric audit,” Med. Phys. 32, 726–732 (2005). 9Asahi Techno Glass Corporation, Explanation material of RPL glass dosimeter: Small element system, Tokyo, Japan, 2000. 10E. G. Yukihara, E. M. Yoshimura, T. D. Lindstrom, S. Ahmad, K. K. Taylor, and G. Mardirossian, “High-precision dosimetry for radiotherapy using the optically stimulated luminescence technique and thin Al2O3:C dosimeters,” Phys. Med. Biol. 50, 5619–5628 (2005). 11J. Lye, L. Dunn, J. Kenny, J. Lehmann, T. Kron, C. Oliver, D. Butler, A. Alves, P. Johnston, R. Franich, and I. Williams, “Remote auditing of radiotherapy facilities using optically stimulated luminescence dosimeters,” Med. Phys. 41, 032102 (10pp.) (2014). 12S. B. Scarboro, D. S. Followill, J. R. Kerns, R. A. White, and S. F. Kry, “Energy response of optically stimulated luminescent dosimeters for nonreference measurement locations in a 6 MV photon beam,” Phys. Med. Biol. 57, 2505–2515 (2012). 13D. W. Kim, W. K. Chung, D. O. Shin, M. Yoon, U. J. Hwang, J. E. Rah, H. Jeong, S. Y. Lee, D. Shin, S. B. Lee, and S. Y. Park, “Dose response of commercially available optically stimulated luminescent detector, Al2O3:C for megavoltage photons and electrons,” Radiat. Prot. Dosim. 149, 101–108 (2012). 14A. Viamonte, L. A. da Rosa, L. A. Buckley, A. Cherpak, and J. E. Cygler, “Radiotherapy dosimetry using a commercial OSL system,” Med. Phys. 35, 1261–1266 (2008). 15L. Dunn, J. Lye, J. Kenny, J. Lehmann, I. Williams, and T. Kron, “Commissioning of optically stimulated luminescence dosimeters for use in radiotherapy,” Radiat. Meas. 51–52, 31–39 (2013). 16J. Aguirre, P. Alvarez, D. Followill, G. Ibbott, C. Amador, and A. Tailor, “Optically stimulated light dosimetry: Commissioning of an optically stimulated luminescence (OSL) system for remote dosimetry audits, the Radiological Physics Center experience,” Med. Phys. 36, 2591–2592 (2009).

Application of a radiophotoluminescent glass dosimeter to nonreference condition dosimetry in the postal dose audit system.

The purpose of this study was to obtain a set of correction factors of the radiophotoluminescent glass dosimeter (RGD) output for field size changes a...
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