CyberKnife beam output factor measurements: A multi-site, multi-detector study

Masi, L.; Russo, S.; Demartin, E.; Doro, R.; Frassanito, C.; Fumagalli, M.L.; Marinelli, M.; Martinotti, A.S.; Pimpinella, M.; Verona, C.; Rondi, E.; Vigorito, S.; Vite, C.; Mancosu, P.

doi:10.1016/j.ejmp.2016.01.149

Cited by 5 publications

(12 citation statements)

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“…First, they calculated field output correction factors for the mD detector following the manufacturer's blueprints of its design and components. In this part of the study, they found a similar response of the mD detector for the smallest field sizes as it was reported in several other MC studies . However, they found that the dimensions of the mD detector did not match those stated by the manufacturer, which brought them to repeat the calculations based on the new data for the active volume of the mD detector.…”

Section: Discussionsupporting

confidence: 74%

“…Remarkably, published data show specific pattern for the smallest fields around 0.5 cm. MC studies and hybrid studies (partly MC, partly experimental) report

k_{Q_{italicclin}, Q_{italicref}}^{f_{italicclin}, f_{italicref}}

values which are close to unity or slightly higher, indicating that an under‐response (increase of

k_{Q_{italicclin}, Q_{italicref}}^{f_{italicclin}, f_{italicref}}

values compared to the next larger field size) of the mD detector was observed for the smallest field size. On the contrary, in several experimental studies, authors have found a rather continuous increase of over‐response of the mD detector down to the smallest field sizes, yielding

k_{Q_{italicclin}, Q_{italicref}}^{f_{italicclin}, f_{italicref}}

values, which are always few percent below unity …”

Section: Discussionmentioning

confidence: 98%

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A novel method for the determination of field output factors and output correction factors for small static fields for six diodes and a microdiamond detector in megavoltage photon beams

et al. 2018

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Purpose The goal of this work is to provide a large and consistent set of data for detector‐specific output correction factors, kQitalicclin,Qitalicref0.166667emfitalicclin,fref, for small static fields for seven solid‐state detectors and to determine field output factors, ΩQitalicclin,Qitalicreffclin,fref, using EBT3 radiochromic films and W1 plastic scintillator as reference detectors on two different linear accelerators and four megavoltage photon beams. Consistent measurement conditions and recommendations given in the International Code of Practice TRS‐483 for small‐field dosimetry were followed throughout the study. Methods ΩQitalicclin,Qitalicreffclin,fref were determined on two linacs, Elekta Versa HD and Varian TrueBeam, for 6 and 10 MV beams with and without flattening filter and for nine fields ranging from 0.5 × 0.5 cm2 to 10 × 10 cm2. Signal readings obtained with EBT3 radiochromic films and W1 plastic scintillator were fitted by an analytical function. Volume averaging correction factors, determined from two‐dimensional (2D) dose matrices obtained with EBT3 films and fitted to bivariate Gaussian function, were used to correct measured signals. kQitalicclin,Qitalicreffclin,fref were determined empirically for six diodes, IBA SFD, IBA Razor, PTW 60008 P, PTW 60012 E, PTW 60018 SRS, and SN EDGE, and a PTW 60019 microDiamond detector. Results Field output factors and detector‐specific kQitalicclin,Qitalicreffclin,fref are presented in the form of analytical functions as well as in the form of discrete values. It is found that in general, for a given linac, small‐field output factors need to be determined for every combination of beam energy and filtration (WFF or FFF) and field size as the differences between them can be statistically significant (P < 0.05). For different beam energies, the present data for kQitalicclin,Qitalicreffclin,fref are found to differ significantly (P < 0.05) from the corresponding data published in TRS‐483 mostly for the smallest fields (<1.5 cm). For the PTW microDiamond detector, statistically significant differences (P < 0.05) between kQitalicclin,Qitalicreffclin,fref values were found for all investigated beams on an Elekta Versa HD linac for field sizes 0.5 × 0.5 cm2 and 0.8 × 0.8 cm2. Significant differences in kQitalicclin,Qitalicreffclin,fref between beams of a given energy but with and without flattening filters are found for measurements made in small fields (<1.5 cm) at a given linac. Differences in kQitalicclin,Qitalicreffclin,fref are also found when measurements are made at different linacs using the same beam energy filtration combination; for the PTW microDiamond detector, these differences were found to be around 6% and were considered as significant. Conclusions Selection of two reference detectors, EBT3 films and W1 plastic scintillator, and use of an analytical function, is a novel approach for the determination of ΩQitalicclin,Qitalicreffclin,fref for small static fields in megavoltage photon beams. Large set of kQitalicclin,Qitalicreffclin,fref data for s...

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Section: Discussionsupporting

confidence: 74%

“…Remarkably, published data show specific pattern for the smallest fields around 0.5 cm. MC studies and hybrid studies (partly MC, partly experimental) report

k_{Q_{italicclin}, Q_{italicref}}^{f_{italicclin}, f_{italicref}}

values which are close to unity or slightly higher, indicating that an under‐response (increase of

k_{Q_{italicclin}, Q_{italicref}}^{f_{italicclin}, f_{italicref}}

k_{Q_{italicclin}, Q_{italicref}}^{f_{italicclin}, f_{italicref}}

values, which are always few percent below unity …”

Section: Discussionmentioning

confidence: 98%

A novel method for the determination of field output factors and output correction factors for small static fields for six diodes and a microdiamond detector in megavoltage photon beams

et al. 2018

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“…It is worth noting that the Exradin W1 proved to be a reliable tool for small field dosimetry applications such as RT beams commissioning and quality checks 1,29,30) thanks to its water-equivalence. However, the approach adopted for stem effect correction is very sensitive to the irradiation set up [31][32][33][34] .…”

Section: Resultsmentioning

confidence: 99%

Characterization of Yb-doped silica optical fiber as real-time dosimeter

Veronese

Chiodini

Cialdi

et al. 2017

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XIX

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The near-infrared radioluminescence and dosimetric properties of Yb-doped silica optical fibers, coupled with an optical detector prototype based on an avalanche photo-diode, were studied by irradiating the fibers with clinical beams generated by a Varian Trilogy accelerator. The performances of the system in standard and small field sizes have been also investigated comparing the output factor, percent depth dose and off axis ratio measurements of the prototypal dosimetric system with other commercial sensors.The results demonstrated that the drawback due to the stem effect in Yb-doped silica optical fibers can be managed in a simple but effective way by optical filtering. These features, together with the accuracy and precision achieved by Ybdoped fibers in relative dose assessments make the device promising for in-vivo dosimetry studies in radiation therapy.

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“…In detail, 15 full papers. [19][20][21][22][23][28][29][30][31][32][34][35][36]38,40 5 reviews, 18,27,33,37,41 1 editorial, 25 and 3 letters to the editor 24,26,39 were published. A total of more than 100 medical physicists were authors of at least one article, showing high level of members' engagement.…”

Section: B Engagement Metricsmentioning

confidence: 99%

“…28,29,34 The next step was to generate specific output factors curve using effective field size for specific Linac [Truebeam 30see Fig. 1(b)] or robotic Linac CyberKnife 20,31 (standardize phase). As a final step we generalized a relative signal ratio curve in function of effective field size by averaging data available from different Linacs, 22 adopting a crowd knowledge based approach see Fig.…”

Section: B Engagement Metricsmentioning

confidence: 99%

Lean Thinking to manage a national working group on physics aspects of Stereotactic Body Radiation Therapy

Mancosu

Russo

Antonucci³

et al. 2021

Medical Physics

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To report how the adoption of a Lean Thinking mindset in the management of a national working group (WG) on the physics of stereotactic body radiation therapy (SBRT) contributed to achieve SBRT standardization objectives. Methods: Vision for the WG has been established as fragmentation reduction and process harmonization enhancement in SBRT for Italian centers. Two main research themes of the technical aspects of SBRT emerged as areas with major standardization improvement needs, small field dosimetry and SBRT planning comparisons, to be investigated through multi-institutional studies. The management of the WG leveraged on the Lean concept of fostering self-organization in a non-hierarchical environment. Four progressive involvement levels were defined for each study. No specific "scientific" preexperience was required to propose and coordinate a project, just requiring a voluntary commitment. People engagement was measured in terms of number of published articles. The standardization goals have been conducted through a simplified "5S" (Sort, Set in Order, Shine, Standardize, and Sustain) methodology, first considering a phase of awareness (the first three "S"), then identifying and implementing standardization actions (the last two "S"). Results: Since the beginning, 157 medical physicists joined the AIFM/SBRT-WG. Twenty-four papers/reviews/letters have been published in the period 2014-2019 on major radiation oncology journals, authored by >100 physicists (>50% working in small hospitals). Six over 12 first authors worked in peripheral/small hospitals, with no prior publication as first author. These studies contributed to the awareness and standardization phases for both small-field dosimetry and planning. In particular, errors in small-field measurements in 8% of centers were detected thanks to a generalized output factor curve in function of the effective field size created by averaging data available from different Linacs. Furthermore, planner's experience in SBRT was correlated with dosimetric parameters in the awareness phase; while sharing median dose volume histograms (DVHs) reduced variability among centers while keeping the same level of plan complexity. Finally, all the dosimetric parameters statistically significant to the planner experience during the awareness phase, were no longer significantly different in the standardization phase. Conclusions: The experience of our SBRT-WG has shown how a Lean Thinking mindset could foster the SBRT procedure standardization and spread the physics of SBRT knowledge, enhancing personal growth. Our expectation is to inspire other scientific societies that have to deal with fragmented contexts or pursue processes harmonization through Lean principles.

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CyberKnife beam output factor measurements: A multi-site, multi-detector study

Cited by 5 publications

References 0 publications

A novel method for the determination of field output factors and output correction factors for small static fields for six diodes and a microdiamond detector in megavoltage photon beams

A novel method for the determination of field output factors and output correction factors for small static fields for six diodes and a microdiamond detector in megavoltage photon beams

Characterization of Yb-doped silica optical fiber as real-time dosimeter

Lean Thinking to manage a national working group on physics aspects of Stereotactic Body Radiation Therapy

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