Diamond dosimeter for small beam stereotactic radiotherapy

Marsolat, Fanny; Tromson, D.; Tranchant, Nicolas; Pomorski, M.; Lazaro-Ponthus, Delphine; Bassinet, C.; Huet, C.; Derreumaux, S.; Chea, M.; Boisserie, G.; Alvarez, José; Bergonzo, P.

doi:10.1016/j.diamond.2013.01.003

Cited by 16 publications

(16 citation statements)

References 31 publications

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“…The use of research SCDDs has been reported [6][7][8] in conjunction with conventional linear accelerators, with square field sizes from 100 3 100 mm 2 down to 10 3 10 mm 2 as a measured at a 1000-mm source-to-detector distance (SDD). In this work, we present the results using a dedicated stereotactic linear accelerator with circular fields for fixed collimators ranging from 5 to 60 mm, at a nominal SDD of 800 mm, in a 6-MV unflattened photon beam.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of a synthetic single-crystal diamond detector for relative dosimetry measurements on a CyberKnife™

Chalkley¹,

Heyes²

2014

BJR

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Objective: To evaluate a new commercial PTW-60019 microDiamond™ (PTW, Freiburg, Germany) synthetic singlecrystal diamond detector for relative dosimetry measurements on a clinical CyberKnife™ VSI (Accuray Inc., Sunnyvale, CA) system. Methods: Relative output factors (ROFs) were measured for collimator diameters from 5 to 60 mm, and compared with diode [PTW-60017, PTW-60018 and IBA Dosimetry (Schwarzenbruck, Germany) SFD] and ionization chamber (PTW-31014 PinPoint® and PTW-31010 Semiflex) measurements. Beam profiles were measured at a range of depths, and collimator sizes, with the detector stem oriented both parallel and perpendicular to the central axis (CAX). Percentage depth-dose (PDD) curves were obtained for the 60-mm collimator and compared with natural Diamond Detector (PTW-60003) and ionization chamber curves to evaluate energy dependence. Results: Penumbral broadening was noted on profile measurements made with the microDiamond oriented with the stem parallel to the CAX, in comparison with diodes. Oriented perpendicular to the CAX, the profile penumbra was sharper, but stem effects could not be ruled out. The PDD measurements were within 0.5% of ionization chamber measurements, indicating insignificant dose-rate dependence. The ROF for the microDiamond fell between diode and ionization chamber results. Published Monte Carlo-derived CyberKnifespecific factors were applied to the PTW-60017, PTW-60018 and PTW-31014 ROFs, and the microDiamond factors agreed within 2.0% of the mean of these. Conclusion: Over a range of small field relative dosimetry measurements, the microDiamond detector shows excellent spatial resolution, dose-rate independence and water equivalence. Advances in knowledge: The microDiamond is a suitable tool for commissioning stereotactic systems.The CyberKnife™ (Accuray Inc., Sunnyvale, CA) system allows submillimetre positional accuracy for stereotactic radiosurgery (SRS) and stereotactic ablative body radiotherapy treatments. It is operated without a flattening filter, with small field sizes (5-to 60-mm-diameter circular beams) and at a dose rate of the order of 10 Gy min 21, as defined at the depth of maximum dose (15 mm deep) for a 60-mm collimator at an 800-mm source-axis distance. This places an increased demand on the accuracy of dosimetric measurements used for commissioning and quality assurance. The absence of a flattening filter in radiotherapy machines is becoming more widespread, which in turn is leading to an increase in clinical dose rates. It is therefore important to consider dose-rate effects of detectors used for commissioning both stereotactic and conventional fields.Although standard detectors are recognized to be unsuitable for small field applications, owing to dose averaging and perturbation effects, SRS-specific detectors have also been shown to have limitations. Silicon diode detectors exhibit an over-response to low-energy scatter. The relative contribution of this scatter increases with field size, and, for regular field sizes, shielding has been used to compen...

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Section: Methodsmentioning

confidence: 99%

Evaluation of a synthetic single-crystal diamond detector for relative dosimetry measurements on a CyberKnife™

Chalkley¹,

Heyes²

2014

BJR

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“…The characteristics of the synthetic diamond detector (PTW-60019), such as small active volume (0.004 mm 3 ), near water-equivalence (Z eff = 6), and low energy dependence, make it an interesting candidate for small field dose measurements as demonstrated by many authors. [15][16][17][18][19] To our knowledge, no one demonstrated the feasibility of using this synthetic diamond for OFs measurement for LGKP. Profiles in the three directions were also measured for the 4 mm collimator.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a synthetic single‐crystal diamond detector for relative dosimetry on the Leksell Gamma Knife Perfexion radiosurgery system

Mancosu¹,

Reggiori²,

Stravato³

et al. 2015

Medical Physics

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Purpose: To evaluate the new commercial PTW-60019 synthetic single-crystal microDiamond detector (PTW, Freiburg, Germany) for relative dosimetry measurements on a clinical Leksell Gamma Knife Perfexion radiosurgery system. Methods: Detector output ratios (DORs) for 4 and 8 mm beams were measured using a micro- Diamond (PTW-60019), a stereotactic unshielded diode [IBA stereotactic field detector (SFD)], a shielded diode (IBA photon field detector), and GafChromic EBT3 films. Both parallel and transversal acquisition directions were considered for PTW-60019 measurements. Measured DORs were compared to the new output factor reference values for Gamma Knife Perfexion (0.814 and 0.900 for 4 and 8 mm, respectively). Profiles in the three directions were also measured for the 4 mm beam to evaluate full width at half maximum (FWHM) and penumbra and to compare them with the corresponding Leksell GammaPlan profiles. Results: FWHM and penumbra for PTW-60019 differed from the calculated values by less than 0.2 and 0.3 mm, for the parallel and transversal acquisitions, respectively. GafChromic films showed FWHM and penumbra within 0.1 mm. The output ratio obtained with the PTW-60019 for the 4 mm field was 1.6% greater in transverse direction compared to the nominal value. Comparable differences up to 0.8% and 1.0% for, respectively, GafChromic films and SFD were found. Conclusions: The microDiamond PTW-60019 is a suitable detector for commissioning and routine use of Gamma Knife with good agreement of both DORs and profiles in the three directions

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“…Schottky diodes are expected to have very good linearity. Dose-rate linearities have been measured in singlecrystal CVD diamond detectors by a number of groups [6], [9], [22]- [28], several of whom determined a significant nonlinear response as a function of dose-rate [6], [9], [23], [27], [28]. A variety of methodologies were used, including varying the PRF, varying the source current in the case of X-ray sources, and varying the source to detector distance, which is the method that has been used here.…”

Section: Comparison With Microdiamondmentioning

confidence: 99%