High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation

Blanck, Oliver; Masi, Laura; Chan, Mark K.H.; Adamczyk, S.; Albrecht, Christian; Damme, Marie-Christin; Loutfi-Krauss, Britta; Alraun, M; Fehr, R.; Ramm, U.; Siebert, Frank‐André; Stelljes, Tenzin Sonam; Poppinga, Daniela; Poppe, Björn

doi:10.1016/j.ejmp.2016.05.060

Cited by 31 publications

(41 citation statements)

References 23 publications

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“…The 1000SRS seems to provide a high enough sensitivity to detect sub-millimeter drifts when performing daily CyberKnife QA, confirming initial results previously published [4]. Compared to other arrays a higher conformity of detected drift and actual robot shift could be observed.…”

Section: Discussionsupporting

confidence: 78%

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Usability and accuracy of high-resolution detectors for daily quality assurance for robotic radiosurgery

Loutfi-Krauss

Damme

Stelljes

et al. 2017

Current Directions in Biomedical Engineering

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For daily CyberKnife QA a Winston-Lutz-Test (Automated-Quality-Assurance, AQA) is used to determine sub-millimeter deviations in beam delivery accuracy. This test is performed using gafchromic film, an extensive and user-dependent method requiring the use of disposables. We therefore analyzed the usability and accuracy of high-resolution detector arrays. We analyzed a liquid-filled ionization-chamber array (Octavius 1000SRS, PTW, Germany), which has a central resolution of 2.5mm. To test sufficient sensitivity, beam profiles with robot shifts of 0.1mm along the arrays' axes were measured. The detected deviation between the shifted and central profile were compared to the real robot's position. We then compared the results to the SRS-Profiler (SunNuclear, USA) with 4.0mm resolution and to the Nonius (QUART, Germany), a single-line diode detector with 2.8mm resolution. Finally, AQA variance and usability were analyzed performing a number of AQA tests over time, which required the use of specially designed fixtures for each array, and the results were compared to film. Concerning sensitivity, the 1000SRS detected the beam profile shifts with a maximum difference of 0.11mm (mean deviation = 0.03mm) compared to the actual robot shift. The Nonius and SRSProfiler showed differences of up to 0.15mm and 0.69mm with mean deviation of 0.05mm and 0.18mm, respectively. Analyzing the variation of AQA results over time, the 1000SRS showed a comparable standard deviation to film (0.26mm vs. 0.18mm). The SRS-Profiler and the Nonius showed a standard deviation of 0.16mm and 0.24mm, respectively. The 1000SRS seems to provide equivalent accuracy and sensitivity to the gold standard film when performing daily AQA tests. Compared to other detectors in our study the sensitivity as well as the accuracy of the 1000SRS appears to be superior and more user-friendly. Furthermore, no significant modification of the standard AQA procedure is required when introducing 1000SRS for CyberKnife AQA.

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Section: Discussionsupporting

confidence: 78%

“…The chambers cover a maximum field size of 10cm x 10cm with a resolution of 2.5mm in the inner center (5cm x 5cm) and 5mm in the outer field. The 1000SRS was recently investigated regarding delivery quality assurance for the CyberKnife and demonstrated a high performance in comparison to film [4].…”

Section: Methodsmentioning

confidence: 99%

Usability and accuracy of high-resolution detectors for daily quality assurance for robotic radiosurgery

Loutfi-Krauss

Damme

Stelljes

et al. 2017

Current Directions in Biomedical Engineering

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“…If a few auditors conducted onsite measurements for all institutions with their own detectors, inter‐operator and intra‐detector uncertainties will be minimized. Recently, two‐dimensional detector arrays with high spatial resolution using liquid‐filled ionization chambers or silicon diodes have become available. These detectors will be helpful because they can acquire OF det and OCR concurrently.…”

Section: Discussionmentioning

confidence: 99%

Small‐field dosimetry of TrueBeam^TM flattened and flattening filter‐free beams: A multi‐institutional analysis

Akino

Mizuno

Isono

et al. 2019

J Applied Clin Med Phys

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Purpose: Detector-dependent interinstitutional variations of the beam data may lead to uncertainties of the delivered dose to patients. Here we evaluated the interunit variability of the flattened and flattening filter-free (FFF) beam data of multiple TrueBeam (Varian Medical Systems) linear accelerators focusing on the small-field dosimetry.Methods: The beam data of 6-and 10-MV photon beams with and without flattening filter measured for modeling of an iPLAN treatment planning system (BrainLAB) were collected from 12 institutionsten HD120 Multileaf Collimator (MLC) and two Millennium120 MLC. Percent-depth dose (PDD), off-center ratio (OCR), and detector output factors (OF det ) measured with different detectors were evaluated.To investigate the detector-associated effects, we evaluated the inter-unit variations of the OF det before and after having applied the output correction factors provided by the International Atomic Energy Agency (IAEA) Technical Reports Series no. 483.Results: PDD measured with a field size of 5 × 5 mm 2 showed that the data measured using an ionization chamber had variations exceeding 1% from the median values. The maximum difference from median value was 2.87% for 10 MV photon beam. The maximum variations of the penumbra width for OCR with 10 × 10 mm 2 field size were 0.97 mm. The OF det showed large variations exceeding 15% for a field size of 5 × 5 mm 2 . When the output correction factors were applied to the OF det , the variations were greatly reduced. The relative difference of almost all field output factors were within ± 5% from the median field output factors. Conclusion:In this study, the inter-unit variability of small-field dosimetry was evaluated for TrueBeam linear accelerators. The variations were large at a field size of 5 × 5 mm 2 , and most occurred in a detector-dependent manner.

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“…In a recent characterization of the device,41 differences between OFs measurements by the 1000SRS, a synthetic diamond (TM60019, PTW) and a small‐field diode (ETM60017, PTW), were approximately 3.0% for a 5 mm collimator and 1.5% for a 7.5 mm collimator, in agreement with previous investigations 26. The size of the SVs (2.3 × 2.3 × 0.5 mm 3 ) would be responsible for the 3% under‐response for the 5 mm collimator owing to volume‐averaging effect 41. The array sensitivity was investigated by introducing beam shifts by moving the robot with 0.1 mm steps (for the 5, 35, 60 mm diameter fields).…”

Section: Discussionmentioning

confidence: 99%

CyberKnife^® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array

Biasi

Petasecca

Guatelli

et al. 2018

J Applied Clin Med Phys

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PurposeThe challenges of accurate dosimetry for stereotactic radiotherapy (SRT) with small unflattened radiation fields have been widely reported in the literature. In this case, suitable dosimeters would have to offer a submillimeter spatial resolution. The CyberKnife® (Accuray Inc., Sunnyvale, CA, USA) is an SRT‐dedicated linear accelerator (linac), which can deliver treatments with submillimeter positional accuracy using circular fields. Beams are delivered with the desired field size using fixed cones, the InCise™ multileaf collimator or a dynamic variable‐aperture Iris™ collimator. The latter, allowing for field sizes to be varied during treatment delivery, has the potential to decrease treatment time, but its reproducibility in terms of output factors (OFs) and dose profiles (DPs) needs to be verified.MethodsA 2D monolithic silicon array detector, the “Octa”, was evaluated for dosimetric quality assurance (QA) for a CyberKnife system. OFs, DPs, percentage depth‐dose (PDD) and tissue maximum ratio (TMR) were investigated, and results were benchmarked against the PTW SRS diode. Cross‐plane, in‐plane and 2 diagonal dose profiles were measured simultaneously with high spatial resolution (0.3 mm). Monte Carlo (MC) simulations with a GEANT4 (GEometry ANd Tracking 4) tool‐kit were added to the study to support the experimental characterization of the detector response.ResultsFor fixed cones and the Iris, for all field sizes investigated in the range between 5 and 60 mm diameter, OFs, PDDs, TMRs, and DPs in terms of FWHM measured by the Octa were accurate within 3% when benchmarked against the SRS diode and MC calculations.ConclusionsThe Octa was shown to be an accurate dosimeter for measurements with a 6 MV FFF beam delivered with a CyberKnife system. The detector enabled real‐time dosimetric verification for the variable aperture Iris collimator, yielding OFs and DPs consistent with those obtained with alternative methods.

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High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation

Cited by 31 publications

References 23 publications

Usability and accuracy of high-resolution detectors for daily quality assurance for robotic radiosurgery

Usability and accuracy of high-resolution detectors for daily quality assurance for robotic radiosurgery

Small‐field dosimetry of TrueBeam^TM flattened and flattening filter‐free beams: A multi‐institutional analysis

CyberKnife^® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array

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High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation

Cited by 31 publications

References 23 publications

Usability and accuracy of high-resolution detectors for daily quality assurance for robotic radiosurgery

Usability and accuracy of high-resolution detectors for daily quality assurance for robotic radiosurgery

Small‐field dosimetry of TrueBeamTM flattened and flattening filter‐free beams: A multi‐institutional analysis

CyberKnife® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array

Contact Info

Product

Resources

About

Small‐field dosimetry of TrueBeam^TM flattened and flattening filter‐free beams: A multi‐institutional analysis

CyberKnife^® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array