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n carbon therapeutic beam dosimetry
Author’s Accepted Manuscript Application of Al 2O3:C+fibre dosimeters for 290MeV/n carbon therapeustic beam dosimetry. L. F Nascimento, F. Vanhavere, S Kodaira, H Kitamura, D. Verellen, Y. De Deene www.elsevier.com/locate/radphyschem
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S0969-806X(15)00229-7 http://dx.doi.org/10.1016/j.radphyschem.2015.06.001 RPC6840
To appear in: Radiation Physics and Chemistry Received date: 7 October 2014 Accepted date: 1 June 2015 Cite this article as: L. F Nascimento, F. Vanhavere, S Kodaira, H Kitamura, D. Verellen and Y. De Deene, Application of Al 2O3:C+fibre dosimeters for 290MeV/n carbon therapeustic beam dosimetry., Radiation Physics and Chemistry, http://dx.doi.org/10.1016/j.radphyschem.2015.06.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Application of Al2O3:C+fibre dosimeters for 290 MeV/n carbon therapeutic beam dosimetry. a
Nascimento, L. Fa,b,d*; Vanhavere, F.b; Kodaira, Se; Kitamura, He; Verellen, D.d; De Deene, Y.a,c Gent University, Department Radiotherapy and Experimental Cancer Research, De Pintelaan, 185. 9000 Gent, Belgium b SCK•CEN Belgian Nuclear Research Centre, Boeretang 200, Mol, Belgium c Institute of Medical Physics. School of Physics - University of Sydney, Australia d University of Brussels (VUB), UZ Brussel, Radiotherapie, Groep Medische Fysica, Brussels, Belgium e Radiation Measurement Research Section, National Institute of Radiological Sciences, Chiba, Japan *[email protected]
Abstract The capability of radioluminescence (RL) dosimeters composed of carbon-doped aluminium oxide (Al2O3:C) detectors + optical fibre has been verified for absorbed dose-rate measurements during carbon radiotherapy. The RL signals from two separate Al2O3:C detectors (single crystal 'CG' and droplet 'P1') have been systematically measured and compared along the Bragg-curve and SpreadOut Bragg-Peak of 290 MeV/n carbon beams in the water. The absorbed dose response was assessed for the range of 0.5 to 10 Gy. For doses up to 6 Gy, we observed a linear response for both types of detectors, while for higher doses CG presented a more prominent supraliearity than P1. The RL response for low-LET protons in the entrance from the curve was found to closely resemble that observed for a clinical 6 MV X-ray beam, while it was found that P1 has a better agreement with the reference data from standard ionization chamber than CG. We observed a significant decrease in luminescence efficiency with LET in the Bragg peak region. The Al2O3:C RL luminescence efficiency differs from Al2O3:C OSL results, which implies that the signal can be corrected for LET dependency to match the correct SOBP and Bragg Peak.
Introduction A portable instrument has been developed for the routine assessment of patient exposure to ionizing radiation during radiotherapy treatments. Carbon-doped aluminium oxide (Al2O3:C) is a highly sensitive luminescence dosimeter material for ionizing radiation. It has been used for absorbed-dose measurements as an optically stimulated luminescence detector in several applications [1-3]. Additionally, during irradiation, Al2O3:C also emits prompt radioluminescence (RL) which primarily arises from electron–hole recombination at F-centres in the crystal (lifetime 35 ms; mean wavelength 420 nm)[4]. While proton radiotherapy has been performed for quite a while [5-7], radiotherapy with heavier ions has only recently gained considerable interest [8-10]. Heavier ions are known to exhibit a significantly increased biological effectiveness especially in the Bragg peak [9]. While for clinical application of proton radiotherapy a constant RBE of 1.1 is adopted, the RBE for carbon ions is much larger (e.g. 2.5 in the target) and, moreover, varies significantly within the patient, e.g. with energy and tissue type [11]. There is, in consequence, a clear interest on the development of therapy systems using heavy charged particles, such as carbon ions. The increased interest in light ion therapy in the last few years has led to considerable efforts to improve the accuracy of carbon ion dosimetry. In comparison to electron, photon or proton dosimetry, carbon ion dosimetry has to be developed and is currently connected with larger uncertainties [12]. Currently, practiced protocols for clinical proton/HCP dosimetry, such as the AAPM report 16 [13], ECHED code of practice and its supplement [14, 15], ICRU report 59 [16] and IAEA TRS-398 [17] recommend cylindrical ionization chambers as reference instruments without taking into account any correction factors for the presence of the ionization chambers in the field. The overall uncertainty in the determination of the absorbed dose in an ion beam is quoted to be 1
2.8% for cylindrical chambers and 3.2% for plane-parallel chambers. The largest contribution to this uncertainty arises from the stopping power ratio water-to-air that is estimated to be 2% [18]. Generally, depth dose distributions of heavy ions have a very sharp Bragg peak—on the order of 1 mm, depending on the beam energy and particle species. Moreover, dose changes with steep gradients in depth and that brings the necessity of dosimetric solutions with high spatial resolution. Such dosimetric system is not yet available, which indicates the necessity for research and development in this field. The Al2O3:C fibre probes have the potential to be used, not only for measurements on skin at the entrance and exit fields but also, for example, by positioning the probes in cavities for real in vivo dosimetry of head-and-neck cancer patients undergoing external beam therapy or in brachytherapy [19]. The prime features of the prototype are that it is accurate enough to detect dose errors and that the probes are small enough to be used for in vivo measurements, not influencing the treatment and disturbing the patient. Al2O3:C optically stimulated and thermoluminescence detectors have been investigated for heavy charged particle (HCP) dosimetry in two challenging dosimetry problems: space and charged particle therapy [20]. One of the problems observed is that the relative response (luminescence efficiency) of TLDs and OSLDs varies with LET and with the particular energy distribution inside the detectors, therefore requiring corrections. The possibility of using OSLDs for precise dosimetry in proton and carbon therapy has been tested using optical fibre systems, also including radioluminescence [21, 22]. In this work, we investigate the potential use of RL from Al2O3:C for carbon dosimetry under conditions similar to those used in medical treatments, while comparing two detector's shapes (single crystal and droplet). The aim of this study is to verify a protocol for in-vivo real time dosimetry in carbon therapeutic beams. Materials and Methods Irradiations were carried out in a 290 MeV/n Carbon mono-energetic pencil-like beam, extracted from an upper synchrotron of HIMAC (Heavy Ion Medical Accelerator in Chiba) at NIRS (National Institute of Radiological Sciences), broadened to 100 mm in diameter with thin metal sheets used as a scatter, and a pair of wobbler magnets [10], in the same manner as in the cases of therapy. Better than ±2% lateral dose uniformity was achieved by this method. In addition, SOBP (Spread-Out BraggPeak) 290 MeV/n Carbon beam was provided with ridge filter for making 6 cm depth in tumour based on the radiation therapy protocol [10]. The distance between the wobbler magnets and the irradiation site was about 7 m. At the centre of the irradiation field, the beam could be regarded as being parallel to the beam axis. The duration and period of the beam spill was 3.3 s. The fibre probes were positioned in front of a Polymethylmethacrylate (PMMA, density = 1.19 g cm−3) binary filter with water-equivalent thickness (mmW-eq.). The stopping power and the total nuclear reaction cross section of PMMA against carbon ions are proportional to those of water to high accuracy all over this relativistic energy domain [23, 24] and the measurement was carried out by inserting various thicknesses of the binary filter into the beam line. Reference data (absorbed doses and depth-dose profiles) were acquired using a Markus ionization chamber [25] and parallel plate ionization chamber [26]. Supplementary 6 MV X-ray irradiations were carried out at Brussels University Hospital (UZBrussel), Aalst-Belgium, using an Elekta Compact system (Elekta AB, Sweden) linear accelerator and a solidwater phantom. The purpose of these irradiations is to compare the RL signal with high LET (Carbon) with the low LET from photons. Two fibre probes were used: 'CG', with Al2O3:C crystal (2×1×1 mm3); and 'P1', with Al2O3:C droplet [27] (r= 0.5mm and l=200m). The detectors, provided by Landauer Inc, were dosed prior to the carbon experiments so as to fill deep traps and use the detector saturated [28]. A bialkali P30USB PMT (Sens-TechTM) photomultiplier tube readouts the radioluminescence from the probes, while two 2 mm 425nm Hard Coated Broadband Bandpass Interference Filter (Edmund Optics) block the influence of stem effect [29]. All measurements were performed at a rate of 10 samples per second. 2
Data acquisition and control were performed using a NI USB 6341 card (National Instruments, USA), via a Labview software. Further description of the RL prototype can be found elsewhere [30]. The relative luminescence efficiency ηk,l used here was adapted by Sawakuchi et. al [31] from KalefEzra and Horowitz [32]. This is defined as the ratio of the luminescence signal to the radiation field k and the luminescence signal to a reference radiation field l, as in Equation 1: Eq. 1 Where Sk and Sl are the luminescence signals (RL) detected after irradiation by the radiation fields k and l, respectively. The LET dependence of OSL Al2O3:C detectors was assessed in previous works for protons and carbon beams [33], Figure 1. For 290 MeV/n the entrance LET is 13.26 keV/m (mono beam) and the luminescence efficiency obtained from Al2O3:C-OSL measurements is 0.782 ± 0.005 (compared to 60 Co). In an attempt to find if similar efficiencies can be observed for radioluminescence we used the Al2O3:C vs. LET curve from Yukihara et al [34] to compare with our results. The Bragg-peak and SOBP results are presented as follows: each data obtained at different depths are normalized to the measured data at d = 0 mmW-eq, which is the same as normalizing to 13.26 keV/m LET (ηk,l, where k is any point measured and l is the value measured at d = 0 mmW-eq).
Figure 1. Relative luminescence efficiency vs. LET for Al2O3:C detectors readout as OSL dosemeters. Extracted from [34].
The stem effect in these measurements was measured using a bare fibre in the same irradiation conditions used for 'CG' and 'P1'. Less than 0.1% signal for the carbon ion beam was measured. Therefore no stem effect correction was applied. Results The dose–response of the detectors in the 0.5–10 Gy dose range was investigated for 290 MeV/n carbons at depth '0' mmw-eq. (at the entrance of the phantom, with 2.42 Gy/min). Figure 2 and Figure 3 show the integrated radioluminescence intensity for CG and P1, respectively. Each point is the average of three independent irradiations and error bars are the standard deviation (1 sd). The RL dose–response for photon-rays (6 MV) was also included for comparison in both graphs. The data for carbon and 6 MV photons was normalized to their respective value at 1 Gy. The supralinearity factor of the RL shows a similar behaviour for carbons and photons when comparing the same detectortype; the dose–response is linear up to about 6 Gy for probe CG and 7 Gy for probe P1. The response becomes supralinear for higher doses. The degree of supralinearity does not appear to depend on type of radiation, but with type of detector.
3
Residuals (%)
Figure 2. Dose-response obtained from the CG fibre irradiated with 290 MeV/n carbon (blue symbols) and 6 MV photons (green symbols) from 0.2 to 10 Gy. Upper-right graph is the dose-response up to 2 Gy and bottom-right graph is the residuals (in %) for CG compared to the expected linearity.
Residuals (%)
Figure 3. Dose-response obtained from the P1 fibre irradiated with 290 MeV/n carbon (blue symbols) from 0.5 to 10 Gy and 6 MV photons (grey symbols) from 0.2 to 9 Gy. Upper-right graph is the dose-response up to 2 Gy and bottom-right graph is the residuals (in %) for P1 compared to the expected linearity.
The Al2O3:C OSL sensitivity changes with irradiation history due to the filling of deep electron and hole traps that act as competitors during irradiation and readout [35], a phenomenon that is generally linked to supralinearity. The same effect appears to be also present in the radioluminescence results found previously [36] and also for CG (Figure 2) and P1 (Figure 3). The OSL dose response to beta rays and high-energy protons was found to be similar, regardless of the detection filter, when comparing 90Sr/90Y and H 1000 MeV beams [20]. Doses were linear up to few grays and entered a supralinear regime. This indicates that the pattern of energy deposition for both types of radiation is similar. The same indication is seen for the results comparing 290 MeV/n carbon beams and 6 MV photons. The supralinearity observed for CG is, on average, twice the value observed for P1 at the same dose, for values from 6 to 10 Gy. The residuals in Figure 2 (above 6 Gy) and Figure 3 (above 7 Gy) show a quadratic polynomial behaviour, i.e., the difference between measured and given dose do not increase linearly (in the range observed). The ratio between the average from the absolute values for RL in carbon (SC) and 6 MV photons (S6MV) gives the luminescence efficiency as follows:
and are calculated using the average of luminescence efficiencies from Figures 2 and 3 from 0.5 to 2 Gy. The errors are the standard deviation.
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Figure 4. Upper graph presents the calculated luminescence efficiencies (ηk,l) from 290 MeV/n mono beam dose distributions in water for P1 and CG. Lower graph compares the reference obtained with the ionization chamber with P1 and CG (values, Si, are normalized by the first point, at '0' mm W-eq, S'0' mmW-eq). Insert graph is the Bragg-peak and 'tail' region in detail.
Figure 5. RL k,l Bragg-curve comparison from irradiations of P1 using the same nominal dose (0.5 Gy), but two different dose rates: ̇ = 2.42 Gy/min and ̇ = 0.60 Gy/min. Measured values, Si, are normalized by the first point, at '0' mmWeq, S'0' mmW-eq.
Irradiations with carbons at the entrance of the phantom and at different water equivalent depths were performed to investigate the radioluminescence detectors energy response and performance for measurements in the pristine (BP) and Spread-Out Bragg-Peak (SOBP). Figure 4 shows the luminescence efficiency ( calculated from the radioluminescence from the probes at different water equivalent depths, irradiated with 0.5 Gy nominal dose (2.42 Gy/min). The error bars are the 5
standard deviation from the average of three independent irradiations. A reduction in RL efficiency at the end of the carbon range is evident for both CG and P1. At the end of the carbon range, the detectors are exposed to carbons of lower energy (and higher LET) than the carbon at the entrance of the phantom; for example, for 290 MeV carbons the average LET increases from 13.26 keV/m (in water), at the entrance, to 327.04 keV/m at 149 mm depth (calculated using SRIM [37]). The increase in LET is associated with saturation of the radioluminescence signal along the particle track, causing a reduction in the RL efficiency. Previous investigations, in the context of space dosimetry, observed a decrease in efficiency for increasing linear energy transfer (LET) of the radiation for Al2O3:C, when used as an OSL detector [31]. An additional test compared the RL signal from fibre P1 on two different dose rates ( ̇ = 2.42 Gy/min and ̇ = 0.60 Gy/min), but same nominal absorbed dose (0.5 Gy). Figure 5 presents the RL comparison together with the residuals (difference between both measurements) from 50 to 155 mmW-eq. There is no evidence of dose-rate dependence. Few residuals presented differences above 1% and only one value was higher than 1.5%. The clear difference between CG and P1 efficiencies around the Bragg-peak can be explained by the detector size and the deposition of energy. Andresen et al. [21] found that the initial OSL intensity is energy independent in the energy range investigated when probes are small (<0.5 mm) and doses are less than 0.3 Gy. P1 has a thickness of 200 m, but the average crystal size is in the range from 5 to 40 m, while CG is a single crystal with dimensions in the millimetre scale. The reduction in RL efficiency is less pronounced for measurements at SOBP, as shown in Figure 6, although still observed at the end of the carbon range. In this case, the energy is deposited by carbons with a very broad energy distribution and the average LET is relatively low for most of the measurement depths. Still, there is a clear difference between P1 and CG, where P1 again presents better agreement with the reference data obtained with the ionization chamber. Each irradiation had a nominal given dose of 0.5 Gy (3.69 Gy/min).
Figure 6. Al2O3:C RL values for P1 and CG irradiated with 0.5 Gy 290 MeV/n SOBP beams. Measured values, Si, are normalized by the first point, at '0' mmW-eq, S'0' mmW-eq.
The RL signal was very stable in both measurements. For CG, the relative RL signal is normally distributed with a standard deviation of 0.4%, while for P1 the deviation was 0.2% (reproducibility). The RL response for low-LET carbons in the plateau region of the Bragg curve was found to has LET dependence, while much less than what was observed in the Bragg peak. The Al2O3:C efficiencies for HCP relative to 60Co gamma rays obtained in previous studies [33, 38] show that the efficiencies values are dependent on the material type and readout technique (thermoluminescence, Continuous Wavelength OSL, Pulsed OSL, Radioluminescence) and even on the choice of filters in front of the PMT. Since the dose deposition for a particular heavy charged particle (HCP) is uniquely defined for a particular material and beam, the differences in the efficiency should only be the result of differences in the dose responses, once the efficiency is a convolution of the response of the material 6
(dose response to a low-LET radiation) and the particular radial dose distribution around the HCP track. Because of that, a system that measure Al2O3:C radioluminescence in therapeutic beams can be calibrated to the beam energy in use. Entrance doses, in the plateau region, can be measured and the region from the Bragg-peak and SOBP can be corrected, once LET vs. luminescence efficiency is known. Figure 7 shows the radioluminescence efficiencies k,l vs. the LET for PI, CG and Al2O3:C OSL (Figure 1). The same shape-curve can be noticed for P1 and CG, as both efficiencies drop with high LET, but not when compared to Al2O3:C OSL. Again, a big difference is seen between P1 and CG and further analysis will be needed to further explain these results. Because the prototype uses the same fibre and only needs one single calibration-fibre a LET-dependence curve to correct the radioluminescence can be extracted from Figure 7.
Figure 7. LET vs. k,l dependence for Al2O3:C P1 and CG (RL) and Al2O3:C OSL (Figure 1).
Conclusion In spite of its increased biological effectiveness, dosimetry in ion beam radiotherapy is also based on absorbed dose to water as an operative quantity. As in conventional radiotherapy, the knowledge of the absorbed dose should be as accurate as possible to assure reproducible results within and between radiotherapy units. The response of solid-state detectors such as Al2O3:C can be considerably different from tissue equivalent detectors and highly dependent on the HCP charge and energy [32, 39, 40]. The explanation is that the energy deposited in the solid state detector can be different from the energy deposited in tissue (or water) when both are exposed to the same HCP fluence because of the dependence of the HCP stopping power on the stopping medium [41]. Another reason is that HCPs create high ionization densities within the particle tracks, with doses approaching saturation of the Al2O3:C RL signal within the particle track. As a result, the light emitted per unit energy deposited in the material, is reduced in comparison to detectors exposed to radiation fields that create low ionization density (e.g. high energy gamma rays). Measurements with helium, neon and iron ions [31] demonstrated that the OSL signal is strongly LET dependent, but in monoenergetic beams, the obtained signal shows a linear response up to high fluences. In this study the use of droplets (thin layer of Al2O3:C, P1) made it possible to achieve higher spatial resolution, to better assess the steep gradients of the ion depth-dose curves. The contribution of the stem effect in the measurements was negligible, so these fibres are especially suitable for measurements in ion beams. An apparent difference in relative luminescence efficiency (ηk,l) can be seen for CG and P1, where P1 presented better agreement with respect to the reference data. The relative luminescence efficiency (ηk,l) for radioluminescence apparently does not have the same dependence with LET as observed with Al2O3:C OSL. Crystal size of the detectors is possibly an important aspect for LET dependence in RL. 7
This study shows that the Al2O3:C RL-response is the same (within the experimental uncertainties) for carbons in the plateau region of the Bragg curve. This suggests that Al2O3:C RL could potentially be suitable for medical carbon dosimetry to measure entrance dose. For higher LET, we show that the luminescence efficiency decreases to about 90% (300 keV/m). Further analysis will help to elucidate how is the behaviour of ηk,l with respect to smaller crystal sizes and if the same LET dependence can be seen for other types of HCP, like protons and helium. Acknowledgements This work was performed as a part of accelerator experiments of the Research Project (H323) at NIRS-HIMAC. We would like to express our thanks to HIMAC crews for their kind support throughout the experiments. References 1. Yukihara EG, McKeever SW. Optically stimulated luminescence: fundamentals and applications: John Wiley & Sons; 2011. 2. Aznar MC, Andersen CE, Bøtter-Jensen L, Bäck SÅJ, Mattsson S, Kjær-Kristoffersen F, et al. Real-time optical-fibre luminescence dosimetry for radiotherapy: physical characteristics and applications in photon beams. Physics in medicine and biology. 2004;49(9):1655. 3. Magne S, Ferdinand P, De Carlan L, Bridier A, Isambert A, Hugon R, et al. Online fibre optic OSL in vivo dosimetry for quality assurance of external beam radiation therapy treatments: The ANRTECSAN Codofer Project. IAEA 2010. 4. Peto A, Kelemen A. Radioluminescence properties of alpha-Al2O3 TL dosemeters. Radiation protection dosimetry. 1996;65(1-4):139-42. 5. Wilson RR. Radiological use of fast protons. Radiology. 1946;47(5):487-91. 6. Hong L, Goitein M, Bucciolini M, Comiskey R, Gottschalk B, Rosenthal S, et al. A pencil beam algorithm for proton dose calculations. Physics in medicine and biology. 1996;41(8):1305. 7. Brada M, Bortfeld T, editors. Proton therapy: the present and the future. Seminars in radiation oncology; 2013. 8. Schulz-Ertner D, Tsujii H. Particle radiation therapy using proton and heavier ion beams. Journal of Clinical Oncology. 2007;25(8):953-64. 9. Kraft G. Tumor therapy with heavy charged particles. Progress in Particle and Nuclear Physics. 2000;45:S473-S544. 10. Kanai T, Endo M, Minohara S, Miyahara N, Koyama-ito H, Tomura H, et al. Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy. International Journal of Radiation Oncology Biology Physics. 1999;44(1):201-10. 11. Jäkel O, Krämer M, Karger C, Debus J. Treatment planning for heavy ion radiotherapy: clinical implementation and application. Physics in medicine and biology. 2001;46(4):1101. 12. Fattori G, Riboldi M, Scifoni E, Krämer M, Pella A, Durante M, et al. Dosimetric effects of residual uncertainties in carbon ion treatment of head chordoma. Radiotherapy and Oncology. 2014. 13. Committee ART, Lyman JT. Protocol for Heavy Charged-particle Therapy Beam Dosimetry: A Report of Task Group 20, Radiation Therapy Committee, American Association of Physicists in Medicine: American Association of Physicists in Medicine; 1986. 14. Vynckier S, Bonnett D, Jones D. Code of practice for clinical proton dosimetry. Radiotherapy and oncology. 1991;20(1):53-63. 15. Vynckier S. Dosimetry of clinical neutron and proton beams: an overview of recommendations. Radiation protection dosimetry. 2004;110(1-4):565-72. 16. Vatnitsky S, Moyers M, Miller D, Abell G, Slater JM, Pedroni E, et al. Proton dosimetry intercomparison based on the ICRU report 59 protocol. Radiotherapy and oncology. 1999;51(3):2739.
8
17. TRS-IAEA. 398: Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water. International Atomic Energy Agency, Vienna. 2000. 18. Andreo P. Accuracy requirements in medical radiation dosimetry Proceedings of an International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry. IDOS; 2010. 19. Damkjær SMS. Time-Resolved Luminescence Dosimetry using Fiber-Coupled Al2O3: C and Applications in External Beam Radiotherapy. 2011. 20. Sawakuchi G, Yukihara E, McKeever S, Benton E. Optically stimulated luminescence fluence response of Al2O3: C dosimeters exposed to different types of radiation. Radiation Measurements. 2008;43(2):450-4. 21. Andersen CE, Edmund JM, Medin J, Grusell E, Jain M, Mattsson S. Medical proton dosimetry using radioluminescence from aluminium oxide crystals attached to optical-fiber cables. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2007;580(1):466-8. 22. Edmund JM, Andersen CE, Greilich S. A track structure model of optically stimulated luminescence from Al 2O3:C irradiated with 10–60MeV protons. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2007;262(2):261-75. 23. Schimmerling W, Vosburgh K, Todd P. Measurements of range in matter for relativistic heavy ions. Physical Review B. 1973;7(7):2895. 24. Matsufuji N, Komori M, Sasaki H, Akiu K, Ogawa M, Fukumura A, et al. Spatial fragment distribution from a therapeutic pencil-like carbon beam in water. Physics in medicine and biology. 2005;50(14):3393. 25. Kanai T, Fukumura A, Kusano Y, Shimbo M, Nishio T. Cross-calibration of ionization chambers in proton and carbon beams. Physics in medicine and biology. 2004;49(5):771. 26. Murakami T, Tsujii H, Furusawa Y, Ando K, Kanai T, Yamada S, et al. Medical and other applications of high-energy heavy-ion beams from HIMAC. Journal of nuclear materials. 1997;248:360-8. 27. Nascimento L, Saldarriaga C, Vanhavere F, D'Agostino E, Defraene G, De Deene Y. Characterization of OSL Al2O3:C droplets for medical dosimetry. Radiation Measurements. 2013;56:200-4. 28. Andersen CE, Damkjær SMS, Kertzscher G, Greilich S, Aznar M. Fiber-coupled radioluminescence dosimetry with saturated Al2O3:C crystals: Characterization in 6 and 18 MV photon beams. Radiation Measurements. 2011;46(10):1090-8. 29. Marckmann CJ, Aznar MC, Andersen CE, Bøtter-Jensen L. Influence of the stem effect on radioluminescence signals from optical fibre Al2O3: C dosemeters. Radiation protection dosimetry. 2006;119(1-4):363-7. 30. Nascimento L, Vanhavere F, Boogers E, Vandecasteele J, De Deene Y. Medical Dosimetry Using a RL/OSL Prototype. Radiation Measurements. 2014. 31. Sawakuchi GO, Yukihara E, McKeever S, Benton E, Gaza R, Uchihori Y, et al. Relative optically stimulated luminescence and thermoluminescence efficiencies of Al2O3: C dosimeters to heavy charged particles with energies relevant to space and radiotherapy dosimetry. Journal of Applied Physics. 2008;104(12):124903. 32. Kalef-Ezra J, Horowitz Y. Heavy charged particle thermoluminescence dosimetry: track structure theory and experiments. The International Journal of Applied Radiation and Isotopes. 1982;33(11):1085-100. 33. Reft CS. The energy dependence and dose response of a commercial optically stimulated luminescent detector for kilovoltage photon, megavoltage photon, and electron, proton, and carbon beams. Medical physics. 2009;36(5):1690-9. 34. Yukihara E, Sawakuchi G, Guduru S, McKeever S, Gaza R, Benton E, et al. Application of the optically stimulated luminescence (OSL) technique in space dosimetry. Radiation measurements. 2006;41(9):1126-35. 9
35. Yukihara E, Whitley V, McKeever S, Akselrod A, Akselrod M. Effect of high-dose irradiation on the optically stimulated luminescence of Al2O3:C. Radiation measurements. 2004;38(3):317-30. 36. Damkjær SMS, Andersen CE, Aznar M. Improved real-time dosimetry using the radioluminescence signal from Al2O3: C. Radiation Measurements. 2008;43(2):893-7. 37. Ziegler JF. SRIM-2003. Nuclear instruments and methods in physics research section B: Beam interactions with materials and atoms. 2004;219:1027-36. 38. Sawakuchi GO, Sahoo N, Gasparian PB, Rodriguez MG, Archambault L, Titt U, et al. Determination of average LET of therapeutic proton beams using Al2O3: C optically stimulated luminescence (OSL) detectors. Physics in medicine and biology. 2010;55(17):4963. 39. Olko P. The microdosimetric one-hit detector model for calculating the response of solid state detectors. Radiation measurements. 2002;35(3):255-67. 40. Sawakuchi GO, Yukihara EG. Analytical modeling of relative luminescence efficiency of Al2O3: C optically stimulated luminescence detectors exposed to high-energy heavy charged particles. Physics in medicine and biology. 2012;57(2):437. 41. Attix FH. Introduction to radiological physics and radiation dosimetry: John Wiley & Sons; 2008.
Highlights
Radioluminescence (RL) real time signal from Al2O3:C+fibre probes. Irradiations with 290 MeV/n Carbon. Two types of detectors were tested: droplet and single crystal. Luminescence efficiencies for each probe were compared with 6 MV photons. Bragg Peak and SOBP are obtained. Luminescence efficiencies for Optically Stimulated Luminescence (OSL) and RL are compared for Al2O3:C
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PII: DOI: Reference:
S0969-806X(15)00229-7 http://dx.doi.org/10.1016/j.radphyschem.2015.06.001 RPC6840
To appear in: Radiation Physics and Chemistry Received date: 7 October 2014 Accepted date: 1 June 2015 Cite this article as: L. F Nascimento, F. Vanhavere, S Kodaira, H Kitamura, D. Verellen and Y. De Deene, Application of Al 2O3:C+fibre dosimeters for 290MeV/n carbon therapeustic beam dosimetry., Radiation Physics and Chemistry, http://dx.doi.org/10.1016/j.radphyschem.2015.06.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Application of Al2O3:C+fibre dosimeters for 290 MeV/n carbon therapeutic beam dosimetry. a
Nascimento, L. Fa,b,d*; Vanhavere, F.b; Kodaira, Se; Kitamura, He; Verellen, D.d; De Deene, Y.a,c Gent University, Department Radiotherapy and Experimental Cancer Research, De Pintelaan, 185. 9000 Gent, Belgium b SCK•CEN Belgian Nuclear Research Centre, Boeretang 200, Mol, Belgium c Institute of Medical Physics. School of Physics - University of Sydney, Australia d University of Brussels (VUB), UZ Brussel, Radiotherapie, Groep Medische Fysica, Brussels, Belgium e Radiation Measurement Research Section, National Institute of Radiological Sciences, Chiba, Japan *[email protected]
Abstract The capability of radioluminescence (RL) dosimeters composed of carbon-doped aluminium oxide (Al2O3:C) detectors + optical fibre has been verified for absorbed dose-rate measurements during carbon radiotherapy. The RL signals from two separate Al2O3:C detectors (single crystal 'CG' and droplet 'P1') have been systematically measured and compared along the Bragg-curve and SpreadOut Bragg-Peak of 290 MeV/n carbon beams in the water. The absorbed dose response was assessed for the range of 0.5 to 10 Gy. For doses up to 6 Gy, we observed a linear response for both types of detectors, while for higher doses CG presented a more prominent supraliearity than P1. The RL response for low-LET protons in the entrance from the curve was found to closely resemble that observed for a clinical 6 MV X-ray beam, while it was found that P1 has a better agreement with the reference data from standard ionization chamber than CG. We observed a significant decrease in luminescence efficiency with LET in the Bragg peak region. The Al2O3:C RL luminescence efficiency differs from Al2O3:C OSL results, which implies that the signal can be corrected for LET dependency to match the correct SOBP and Bragg Peak.
Introduction A portable instrument has been developed for the routine assessment of patient exposure to ionizing radiation during radiotherapy treatments. Carbon-doped aluminium oxide (Al2O3:C) is a highly sensitive luminescence dosimeter material for ionizing radiation. It has been used for absorbed-dose measurements as an optically stimulated luminescence detector in several applications [1-3]. Additionally, during irradiation, Al2O3:C also emits prompt radioluminescence (RL) which primarily arises from electron–hole recombination at F-centres in the crystal (lifetime 35 ms; mean wavelength 420 nm)[4]. While proton radiotherapy has been performed for quite a while [5-7], radiotherapy with heavier ions has only recently gained considerable interest [8-10]. Heavier ions are known to exhibit a significantly increased biological effectiveness especially in the Bragg peak [9]. While for clinical application of proton radiotherapy a constant RBE of 1.1 is adopted, the RBE for carbon ions is much larger (e.g. 2.5 in the target) and, moreover, varies significantly within the patient, e.g. with energy and tissue type [11]. There is, in consequence, a clear interest on the development of therapy systems using heavy charged particles, such as carbon ions. The increased interest in light ion therapy in the last few years has led to considerable efforts to improve the accuracy of carbon ion dosimetry. In comparison to electron, photon or proton dosimetry, carbon ion dosimetry has to be developed and is currently connected with larger uncertainties [12]. Currently, practiced protocols for clinical proton/HCP dosimetry, such as the AAPM report 16 [13], ECHED code of practice and its supplement [14, 15], ICRU report 59 [16] and IAEA TRS-398 [17] recommend cylindrical ionization chambers as reference instruments without taking into account any correction factors for the presence of the ionization chambers in the field. The overall uncertainty in the determination of the absorbed dose in an ion beam is quoted to be 1
2.8% for cylindrical chambers and 3.2% for plane-parallel chambers. The largest contribution to this uncertainty arises from the stopping power ratio water-to-air that is estimated to be 2% [18]. Generally, depth dose distributions of heavy ions have a very sharp Bragg peak—on the order of 1 mm, depending on the beam energy and particle species. Moreover, dose changes with steep gradients in depth and that brings the necessity of dosimetric solutions with high spatial resolution. Such dosimetric system is not yet available, which indicates the necessity for research and development in this field. The Al2O3:C fibre probes have the potential to be used, not only for measurements on skin at the entrance and exit fields but also, for example, by positioning the probes in cavities for real in vivo dosimetry of head-and-neck cancer patients undergoing external beam therapy or in brachytherapy [19]. The prime features of the prototype are that it is accurate enough to detect dose errors and that the probes are small enough to be used for in vivo measurements, not influencing the treatment and disturbing the patient. Al2O3:C optically stimulated and thermoluminescence detectors have been investigated for heavy charged particle (HCP) dosimetry in two challenging dosimetry problems: space and charged particle therapy [20]. One of the problems observed is that the relative response (luminescence efficiency) of TLDs and OSLDs varies with LET and with the particular energy distribution inside the detectors, therefore requiring corrections. The possibility of using OSLDs for precise dosimetry in proton and carbon therapy has been tested using optical fibre systems, also including radioluminescence [21, 22]. In this work, we investigate the potential use of RL from Al2O3:C for carbon dosimetry under conditions similar to those used in medical treatments, while comparing two detector's shapes (single crystal and droplet). The aim of this study is to verify a protocol for in-vivo real time dosimetry in carbon therapeutic beams. Materials and Methods Irradiations were carried out in a 290 MeV/n Carbon mono-energetic pencil-like beam, extracted from an upper synchrotron of HIMAC (Heavy Ion Medical Accelerator in Chiba) at NIRS (National Institute of Radiological Sciences), broadened to 100 mm in diameter with thin metal sheets used as a scatter, and a pair of wobbler magnets [10], in the same manner as in the cases of therapy. Better than ±2% lateral dose uniformity was achieved by this method. In addition, SOBP (Spread-Out BraggPeak) 290 MeV/n Carbon beam was provided with ridge filter for making 6 cm depth in tumour based on the radiation therapy protocol [10]. The distance between the wobbler magnets and the irradiation site was about 7 m. At the centre of the irradiation field, the beam could be regarded as being parallel to the beam axis. The duration and period of the beam spill was 3.3 s. The fibre probes were positioned in front of a Polymethylmethacrylate (PMMA, density = 1.19 g cm−3) binary filter with water-equivalent thickness (mmW-eq.). The stopping power and the total nuclear reaction cross section of PMMA against carbon ions are proportional to those of water to high accuracy all over this relativistic energy domain [23, 24] and the measurement was carried out by inserting various thicknesses of the binary filter into the beam line. Reference data (absorbed doses and depth-dose profiles) were acquired using a Markus ionization chamber [25] and parallel plate ionization chamber [26]. Supplementary 6 MV X-ray irradiations were carried out at Brussels University Hospital (UZBrussel), Aalst-Belgium, using an Elekta Compact system (Elekta AB, Sweden) linear accelerator and a solidwater phantom. The purpose of these irradiations is to compare the RL signal with high LET (Carbon) with the low LET from photons. Two fibre probes were used: 'CG', with Al2O3:C crystal (2×1×1 mm3); and 'P1', with Al2O3:C droplet [27] (r= 0.5mm and l=200m). The detectors, provided by Landauer Inc, were dosed prior to the carbon experiments so as to fill deep traps and use the detector saturated [28]. A bialkali P30USB PMT (Sens-TechTM) photomultiplier tube readouts the radioluminescence from the probes, while two 2 mm 425nm Hard Coated Broadband Bandpass Interference Filter (Edmund Optics) block the influence of stem effect [29]. All measurements were performed at a rate of 10 samples per second. 2
Data acquisition and control were performed using a NI USB 6341 card (National Instruments, USA), via a Labview software. Further description of the RL prototype can be found elsewhere [30]. The relative luminescence efficiency ηk,l used here was adapted by Sawakuchi et. al [31] from KalefEzra and Horowitz [32]. This is defined as the ratio of the luminescence signal to the radiation field k and the luminescence signal to a reference radiation field l, as in Equation 1: Eq. 1 Where Sk and Sl are the luminescence signals (RL) detected after irradiation by the radiation fields k and l, respectively. The LET dependence of OSL Al2O3:C detectors was assessed in previous works for protons and carbon beams [33], Figure 1. For 290 MeV/n the entrance LET is 13.26 keV/m (mono beam) and the luminescence efficiency obtained from Al2O3:C-OSL measurements is 0.782 ± 0.005 (compared to 60 Co). In an attempt to find if similar efficiencies can be observed for radioluminescence we used the Al2O3:C vs. LET curve from Yukihara et al [34] to compare with our results. The Bragg-peak and SOBP results are presented as follows: each data obtained at different depths are normalized to the measured data at d = 0 mmW-eq, which is the same as normalizing to 13.26 keV/m LET (ηk,l, where k is any point measured and l is the value measured at d = 0 mmW-eq).
Figure 1. Relative luminescence efficiency vs. LET for Al2O3:C detectors readout as OSL dosemeters. Extracted from [34].
The stem effect in these measurements was measured using a bare fibre in the same irradiation conditions used for 'CG' and 'P1'. Less than 0.1% signal for the carbon ion beam was measured. Therefore no stem effect correction was applied. Results The dose–response of the detectors in the 0.5–10 Gy dose range was investigated for 290 MeV/n carbons at depth '0' mmw-eq. (at the entrance of the phantom, with 2.42 Gy/min). Figure 2 and Figure 3 show the integrated radioluminescence intensity for CG and P1, respectively. Each point is the average of three independent irradiations and error bars are the standard deviation (1 sd). The RL dose–response for photon-rays (6 MV) was also included for comparison in both graphs. The data for carbon and 6 MV photons was normalized to their respective value at 1 Gy. The supralinearity factor of the RL shows a similar behaviour for carbons and photons when comparing the same detectortype; the dose–response is linear up to about 6 Gy for probe CG and 7 Gy for probe P1. The response becomes supralinear for higher doses. The degree of supralinearity does not appear to depend on type of radiation, but with type of detector.
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Residuals (%)
Figure 2. Dose-response obtained from the CG fibre irradiated with 290 MeV/n carbon (blue symbols) and 6 MV photons (green symbols) from 0.2 to 10 Gy. Upper-right graph is the dose-response up to 2 Gy and bottom-right graph is the residuals (in %) for CG compared to the expected linearity.
Residuals (%)
Figure 3. Dose-response obtained from the P1 fibre irradiated with 290 MeV/n carbon (blue symbols) from 0.5 to 10 Gy and 6 MV photons (grey symbols) from 0.2 to 9 Gy. Upper-right graph is the dose-response up to 2 Gy and bottom-right graph is the residuals (in %) for P1 compared to the expected linearity.
The Al2O3:C OSL sensitivity changes with irradiation history due to the filling of deep electron and hole traps that act as competitors during irradiation and readout [35], a phenomenon that is generally linked to supralinearity. The same effect appears to be also present in the radioluminescence results found previously [36] and also for CG (Figure 2) and P1 (Figure 3). The OSL dose response to beta rays and high-energy protons was found to be similar, regardless of the detection filter, when comparing 90Sr/90Y and H 1000 MeV beams [20]. Doses were linear up to few grays and entered a supralinear regime. This indicates that the pattern of energy deposition for both types of radiation is similar. The same indication is seen for the results comparing 290 MeV/n carbon beams and 6 MV photons. The supralinearity observed for CG is, on average, twice the value observed for P1 at the same dose, for values from 6 to 10 Gy. The residuals in Figure 2 (above 6 Gy) and Figure 3 (above 7 Gy) show a quadratic polynomial behaviour, i.e., the difference between measured and given dose do not increase linearly (in the range observed). The ratio between the average from the absolute values for RL in carbon (SC) and 6 MV photons (S6MV) gives the luminescence efficiency as follows:
and are calculated using the average of luminescence efficiencies from Figures 2 and 3 from 0.5 to 2 Gy. The errors are the standard deviation.
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Figure 4. Upper graph presents the calculated luminescence efficiencies (ηk,l) from 290 MeV/n mono beam dose distributions in water for P1 and CG. Lower graph compares the reference obtained with the ionization chamber with P1 and CG (values, Si, are normalized by the first point, at '0' mm W-eq, S'0' mmW-eq). Insert graph is the Bragg-peak and 'tail' region in detail.
Figure 5. RL k,l Bragg-curve comparison from irradiations of P1 using the same nominal dose (0.5 Gy), but two different dose rates: ̇ = 2.42 Gy/min and ̇ = 0.60 Gy/min. Measured values, Si, are normalized by the first point, at '0' mmWeq, S'0' mmW-eq.
Irradiations with carbons at the entrance of the phantom and at different water equivalent depths were performed to investigate the radioluminescence detectors energy response and performance for measurements in the pristine (BP) and Spread-Out Bragg-Peak (SOBP). Figure 4 shows the luminescence efficiency ( calculated from the radioluminescence from the probes at different water equivalent depths, irradiated with 0.5 Gy nominal dose (2.42 Gy/min). The error bars are the 5
standard deviation from the average of three independent irradiations. A reduction in RL efficiency at the end of the carbon range is evident for both CG and P1. At the end of the carbon range, the detectors are exposed to carbons of lower energy (and higher LET) than the carbon at the entrance of the phantom; for example, for 290 MeV carbons the average LET increases from 13.26 keV/m (in water), at the entrance, to 327.04 keV/m at 149 mm depth (calculated using SRIM [37]). The increase in LET is associated with saturation of the radioluminescence signal along the particle track, causing a reduction in the RL efficiency. Previous investigations, in the context of space dosimetry, observed a decrease in efficiency for increasing linear energy transfer (LET) of the radiation for Al2O3:C, when used as an OSL detector [31]. An additional test compared the RL signal from fibre P1 on two different dose rates ( ̇ = 2.42 Gy/min and ̇ = 0.60 Gy/min), but same nominal absorbed dose (0.5 Gy). Figure 5 presents the RL comparison together with the residuals (difference between both measurements) from 50 to 155 mmW-eq. There is no evidence of dose-rate dependence. Few residuals presented differences above 1% and only one value was higher than 1.5%. The clear difference between CG and P1 efficiencies around the Bragg-peak can be explained by the detector size and the deposition of energy. Andresen et al. [21] found that the initial OSL intensity is energy independent in the energy range investigated when probes are small (<0.5 mm) and doses are less than 0.3 Gy. P1 has a thickness of 200 m, but the average crystal size is in the range from 5 to 40 m, while CG is a single crystal with dimensions in the millimetre scale. The reduction in RL efficiency is less pronounced for measurements at SOBP, as shown in Figure 6, although still observed at the end of the carbon range. In this case, the energy is deposited by carbons with a very broad energy distribution and the average LET is relatively low for most of the measurement depths. Still, there is a clear difference between P1 and CG, where P1 again presents better agreement with the reference data obtained with the ionization chamber. Each irradiation had a nominal given dose of 0.5 Gy (3.69 Gy/min).
Figure 6. Al2O3:C RL values for P1 and CG irradiated with 0.5 Gy 290 MeV/n SOBP beams. Measured values, Si, are normalized by the first point, at '0' mmW-eq, S'0' mmW-eq.
The RL signal was very stable in both measurements. For CG, the relative RL signal is normally distributed with a standard deviation of 0.4%, while for P1 the deviation was 0.2% (reproducibility). The RL response for low-LET carbons in the plateau region of the Bragg curve was found to has LET dependence, while much less than what was observed in the Bragg peak. The Al2O3:C efficiencies for HCP relative to 60Co gamma rays obtained in previous studies [33, 38] show that the efficiencies values are dependent on the material type and readout technique (thermoluminescence, Continuous Wavelength OSL, Pulsed OSL, Radioluminescence) and even on the choice of filters in front of the PMT. Since the dose deposition for a particular heavy charged particle (HCP) is uniquely defined for a particular material and beam, the differences in the efficiency should only be the result of differences in the dose responses, once the efficiency is a convolution of the response of the material 6
(dose response to a low-LET radiation) and the particular radial dose distribution around the HCP track. Because of that, a system that measure Al2O3:C radioluminescence in therapeutic beams can be calibrated to the beam energy in use. Entrance doses, in the plateau region, can be measured and the region from the Bragg-peak and SOBP can be corrected, once LET vs. luminescence efficiency is known. Figure 7 shows the radioluminescence efficiencies k,l vs. the LET for PI, CG and Al2O3:C OSL (Figure 1). The same shape-curve can be noticed for P1 and CG, as both efficiencies drop with high LET, but not when compared to Al2O3:C OSL. Again, a big difference is seen between P1 and CG and further analysis will be needed to further explain these results. Because the prototype uses the same fibre and only needs one single calibration-fibre a LET-dependence curve to correct the radioluminescence can be extracted from Figure 7.
Figure 7. LET vs. k,l dependence for Al2O3:C P1 and CG (RL) and Al2O3:C OSL (Figure 1).
Conclusion In spite of its increased biological effectiveness, dosimetry in ion beam radiotherapy is also based on absorbed dose to water as an operative quantity. As in conventional radiotherapy, the knowledge of the absorbed dose should be as accurate as possible to assure reproducible results within and between radiotherapy units. The response of solid-state detectors such as Al2O3:C can be considerably different from tissue equivalent detectors and highly dependent on the HCP charge and energy [32, 39, 40]. The explanation is that the energy deposited in the solid state detector can be different from the energy deposited in tissue (or water) when both are exposed to the same HCP fluence because of the dependence of the HCP stopping power on the stopping medium [41]. Another reason is that HCPs create high ionization densities within the particle tracks, with doses approaching saturation of the Al2O3:C RL signal within the particle track. As a result, the light emitted per unit energy deposited in the material, is reduced in comparison to detectors exposed to radiation fields that create low ionization density (e.g. high energy gamma rays). Measurements with helium, neon and iron ions [31] demonstrated that the OSL signal is strongly LET dependent, but in monoenergetic beams, the obtained signal shows a linear response up to high fluences. In this study the use of droplets (thin layer of Al2O3:C, P1) made it possible to achieve higher spatial resolution, to better assess the steep gradients of the ion depth-dose curves. The contribution of the stem effect in the measurements was negligible, so these fibres are especially suitable for measurements in ion beams. An apparent difference in relative luminescence efficiency (ηk,l) can be seen for CG and P1, where P1 presented better agreement with respect to the reference data. The relative luminescence efficiency (ηk,l) for radioluminescence apparently does not have the same dependence with LET as observed with Al2O3:C OSL. Crystal size of the detectors is possibly an important aspect for LET dependence in RL. 7
This study shows that the Al2O3:C RL-response is the same (within the experimental uncertainties) for carbons in the plateau region of the Bragg curve. This suggests that Al2O3:C RL could potentially be suitable for medical carbon dosimetry to measure entrance dose. For higher LET, we show that the luminescence efficiency decreases to about 90% (300 keV/m). Further analysis will help to elucidate how is the behaviour of ηk,l with respect to smaller crystal sizes and if the same LET dependence can be seen for other types of HCP, like protons and helium. Acknowledgements This work was performed as a part of accelerator experiments of the Research Project (H323) at NIRS-HIMAC. We would like to express our thanks to HIMAC crews for their kind support throughout the experiments. References 1. Yukihara EG, McKeever SW. Optically stimulated luminescence: fundamentals and applications: John Wiley & Sons; 2011. 2. Aznar MC, Andersen CE, Bøtter-Jensen L, Bäck SÅJ, Mattsson S, Kjær-Kristoffersen F, et al. Real-time optical-fibre luminescence dosimetry for radiotherapy: physical characteristics and applications in photon beams. Physics in medicine and biology. 2004;49(9):1655. 3. Magne S, Ferdinand P, De Carlan L, Bridier A, Isambert A, Hugon R, et al. Online fibre optic OSL in vivo dosimetry for quality assurance of external beam radiation therapy treatments: The ANRTECSAN Codofer Project. IAEA 2010. 4. Peto A, Kelemen A. Radioluminescence properties of alpha-Al2O3 TL dosemeters. Radiation protection dosimetry. 1996;65(1-4):139-42. 5. Wilson RR. Radiological use of fast protons. Radiology. 1946;47(5):487-91. 6. Hong L, Goitein M, Bucciolini M, Comiskey R, Gottschalk B, Rosenthal S, et al. A pencil beam algorithm for proton dose calculations. Physics in medicine and biology. 1996;41(8):1305. 7. Brada M, Bortfeld T, editors. Proton therapy: the present and the future. Seminars in radiation oncology; 2013. 8. Schulz-Ertner D, Tsujii H. Particle radiation therapy using proton and heavier ion beams. Journal of Clinical Oncology. 2007;25(8):953-64. 9. Kraft G. Tumor therapy with heavy charged particles. Progress in Particle and Nuclear Physics. 2000;45:S473-S544. 10. Kanai T, Endo M, Minohara S, Miyahara N, Koyama-ito H, Tomura H, et al. Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy. International Journal of Radiation Oncology Biology Physics. 1999;44(1):201-10. 11. Jäkel O, Krämer M, Karger C, Debus J. Treatment planning for heavy ion radiotherapy: clinical implementation and application. Physics in medicine and biology. 2001;46(4):1101. 12. Fattori G, Riboldi M, Scifoni E, Krämer M, Pella A, Durante M, et al. Dosimetric effects of residual uncertainties in carbon ion treatment of head chordoma. Radiotherapy and Oncology. 2014. 13. Committee ART, Lyman JT. Protocol for Heavy Charged-particle Therapy Beam Dosimetry: A Report of Task Group 20, Radiation Therapy Committee, American Association of Physicists in Medicine: American Association of Physicists in Medicine; 1986. 14. Vynckier S, Bonnett D, Jones D. Code of practice for clinical proton dosimetry. Radiotherapy and oncology. 1991;20(1):53-63. 15. Vynckier S. Dosimetry of clinical neutron and proton beams: an overview of recommendations. Radiation protection dosimetry. 2004;110(1-4):565-72. 16. Vatnitsky S, Moyers M, Miller D, Abell G, Slater JM, Pedroni E, et al. Proton dosimetry intercomparison based on the ICRU report 59 protocol. Radiotherapy and oncology. 1999;51(3):2739.
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17. TRS-IAEA. 398: Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water. International Atomic Energy Agency, Vienna. 2000. 18. Andreo P. Accuracy requirements in medical radiation dosimetry Proceedings of an International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry. IDOS; 2010. 19. Damkjær SMS. Time-Resolved Luminescence Dosimetry using Fiber-Coupled Al2O3: C and Applications in External Beam Radiotherapy. 2011. 20. Sawakuchi G, Yukihara E, McKeever S, Benton E. Optically stimulated luminescence fluence response of Al2O3: C dosimeters exposed to different types of radiation. Radiation Measurements. 2008;43(2):450-4. 21. Andersen CE, Edmund JM, Medin J, Grusell E, Jain M, Mattsson S. Medical proton dosimetry using radioluminescence from aluminium oxide crystals attached to optical-fiber cables. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2007;580(1):466-8. 22. Edmund JM, Andersen CE, Greilich S. A track structure model of optically stimulated luminescence from Al 2O3:C irradiated with 10–60MeV protons. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2007;262(2):261-75. 23. Schimmerling W, Vosburgh K, Todd P. Measurements of range in matter for relativistic heavy ions. Physical Review B. 1973;7(7):2895. 24. Matsufuji N, Komori M, Sasaki H, Akiu K, Ogawa M, Fukumura A, et al. Spatial fragment distribution from a therapeutic pencil-like carbon beam in water. Physics in medicine and biology. 2005;50(14):3393. 25. Kanai T, Fukumura A, Kusano Y, Shimbo M, Nishio T. Cross-calibration of ionization chambers in proton and carbon beams. Physics in medicine and biology. 2004;49(5):771. 26. Murakami T, Tsujii H, Furusawa Y, Ando K, Kanai T, Yamada S, et al. Medical and other applications of high-energy heavy-ion beams from HIMAC. Journal of nuclear materials. 1997;248:360-8. 27. Nascimento L, Saldarriaga C, Vanhavere F, D'Agostino E, Defraene G, De Deene Y. Characterization of OSL Al2O3:C droplets for medical dosimetry. Radiation Measurements. 2013;56:200-4. 28. Andersen CE, Damkjær SMS, Kertzscher G, Greilich S, Aznar M. Fiber-coupled radioluminescence dosimetry with saturated Al2O3:C crystals: Characterization in 6 and 18 MV photon beams. Radiation Measurements. 2011;46(10):1090-8. 29. Marckmann CJ, Aznar MC, Andersen CE, Bøtter-Jensen L. Influence of the stem effect on radioluminescence signals from optical fibre Al2O3: C dosemeters. Radiation protection dosimetry. 2006;119(1-4):363-7. 30. Nascimento L, Vanhavere F, Boogers E, Vandecasteele J, De Deene Y. Medical Dosimetry Using a RL/OSL Prototype. Radiation Measurements. 2014. 31. Sawakuchi GO, Yukihara E, McKeever S, Benton E, Gaza R, Uchihori Y, et al. Relative optically stimulated luminescence and thermoluminescence efficiencies of Al2O3: C dosimeters to heavy charged particles with energies relevant to space and radiotherapy dosimetry. Journal of Applied Physics. 2008;104(12):124903. 32. Kalef-Ezra J, Horowitz Y. Heavy charged particle thermoluminescence dosimetry: track structure theory and experiments. The International Journal of Applied Radiation and Isotopes. 1982;33(11):1085-100. 33. Reft CS. The energy dependence and dose response of a commercial optically stimulated luminescent detector for kilovoltage photon, megavoltage photon, and electron, proton, and carbon beams. Medical physics. 2009;36(5):1690-9. 34. Yukihara E, Sawakuchi G, Guduru S, McKeever S, Gaza R, Benton E, et al. Application of the optically stimulated luminescence (OSL) technique in space dosimetry. Radiation measurements. 2006;41(9):1126-35. 9
35. Yukihara E, Whitley V, McKeever S, Akselrod A, Akselrod M. Effect of high-dose irradiation on the optically stimulated luminescence of Al2O3:C. Radiation measurements. 2004;38(3):317-30. 36. Damkjær SMS, Andersen CE, Aznar M. Improved real-time dosimetry using the radioluminescence signal from Al2O3: C. Radiation Measurements. 2008;43(2):893-7. 37. Ziegler JF. SRIM-2003. Nuclear instruments and methods in physics research section B: Beam interactions with materials and atoms. 2004;219:1027-36. 38. Sawakuchi GO, Sahoo N, Gasparian PB, Rodriguez MG, Archambault L, Titt U, et al. Determination of average LET of therapeutic proton beams using Al2O3: C optically stimulated luminescence (OSL) detectors. Physics in medicine and biology. 2010;55(17):4963. 39. Olko P. The microdosimetric one-hit detector model for calculating the response of solid state detectors. Radiation measurements. 2002;35(3):255-67. 40. Sawakuchi GO, Yukihara EG. Analytical modeling of relative luminescence efficiency of Al2O3: C optically stimulated luminescence detectors exposed to high-energy heavy charged particles. Physics in medicine and biology. 2012;57(2):437. 41. Attix FH. Introduction to radiological physics and radiation dosimetry: John Wiley & Sons; 2008.
Highlights
Radioluminescence (RL) real time signal from Al2O3:C+fibre probes. Irradiations with 290 MeV/n Carbon. Two types of detectors were tested: droplet and single crystal. Luminescence efficiencies for each probe were compared with 6 MV photons. Bragg Peak and SOBP are obtained. Luminescence efficiencies for Optically Stimulated Luminescence (OSL) and RL are compared for Al2O3:C
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