CyberKnife® M6™: Peripheral dose evaluation for brain treatments

Delaby, N.; Bellec, J.; Bouvier, Jeanne; Jouyaux, F.; Perdrieux, M.; Castelli, J.; Lecouillard, I.; Manens, J.-P.; Lafond, C.

doi:10.1016/j.ejmp.2017.04.015

Cited by 6 publications

(5 citation statements)

References 28 publications

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“…At a given distance from the beam axis, the higher dose levels obtained with the large collimators in compariso n with small beam sizes are consistent with literature (Petti et al 2006, Delaby et al 2017. But, it is important to mention that out-of-field dose is highly dependent on the type of secondary collimation used.…”

Section: Validation Of the Penelope Simulation For The Determination ...supporting

confidence: 87%

“…But, it is important to mention that out-of-field dose is highly dependent on the type of secondary collimation used. Indeed, Delaby et al (2017) shows that the Iris ™ decreases by a factor 3 the dose delivered at 15 cm from the PTV border in comparison with fixed collimator. Moreover, the Cyberknife version is also impacting out-of-field doses: Chuang et al (2008) reports that the shielding upgrade of their system decreased the peripheral dose up to 30 cm from the target by a maximum of 59%.…”

Section: Validation Of the Penelope Simulation For The Determination ...mentioning

confidence: 97%

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A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

Colnot¹,

Barraux²,

Loiseau³

et al. 2019

Phys. Med. Biol.

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In a previous work, a PENELOPE Monte Carlo model of a Cyberknife system equipped with fixed collimator was developed and validated for in-field dose evaluation. The aim of this work is to extend it to evaluate peripheral doses and to determine the precision of the treatment planning system (TPS) Multiplan in evaluating the off-axis doses. The Cyberknife® head model was completed with surrounding components based on manufacturer drawings. The contribution of the different head parts on the out-of-field dose was studied. To model the attenuation and the modification of particle energy caused by components not modelled, the photon transport was modified in one of the added components. The model was iteratively adjusted to fit dose profiles measured with EBT3 films and an ionization chamber for several collimator sizes. Finally, dose profiles were calculated using the two Multiplan TPS algorithms and were compared to our simulations. The contributions to out-of-field dose were identified as scattered radiation from the phantom and head leakage and scatter originating at the secondary collimator level. Particle transport in the additional pieces was modified to model this radiation. The maximum differences between simulated and measured doses are of 20.4%. Regarding the detector responses away from axis, EBT3 films and the Farmer chamber give similar response (less than 20% difference). The TPS Monte Carlo algorithm underestimates the doses away from axis more importantly for the smaller field sizes (up to 98%). Besides, RayTracing simplifies peripheral dose to a constant value with no inclusion of particle transport. A Monte Carlo model of a Cyberknife system for the determination of out-of-field doses up to 14 cm off-axis was successfully developed and validated for different depths and field sizes in comparison with measurements. This study also confirms that TPS algorithms do not model peripheral dose properly.

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Section: Validation Of the Penelope Simulation For The Determination ...supporting

confidence: 87%

Section: Validation Of the Penelope Simulation For The Determination ...mentioning

confidence: 97%

A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

Colnot¹,

Barraux²,

Loiseau³

et al. 2019

Phys. Med. Biol.

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“…The PD scatter contributions are affected by the characteristic features of the treatment plan, in particular the type of collimator, monitor unit (MU), aperture size, beam number and orientations, etc. 5,6 . Delaby et al .…”

Section: Introductionmentioning

confidence: 99%

“…Delaby et al . 5 reported that the evaluation of PD received by healthy tissues in brain stereotactic radiotherapy treatment (SRT) using a CyberKnife M6 system demonstrated that PD was approximately 0.06% of MU with a 20-mm fixed collimator and 0.04% of MU with the identical aperture for an IRIS collimator 5 . Although MLC-based plans were not included in their study, the results are unlikely to be markedly different.…”

Section: Introductionmentioning

confidence: 99%

Plan Quality and Secondary Cancer Risk Assessment in Patients with Benign Intracranial Lesions after Radiosurgery using the CyberKnife M6 Robotic Radiosurgery System

Lan¹,

Shieh²,

Liu³

et al. 2019

Sci Rep

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This study was performed to examine the quality of planning and treatment modality using a CyberKnife (CK) robotic radiosurgery system with multileaf collimator (MLC)-based plans and IRIS (variable aperture collimator system)-based plans in relation to the dose–response of secondary cancer risk (SCR) in patients with benign intracranial tumors. The study population consisted of 15 patients with benign intracranial lesions after curative treatment using a CyberKnife M6 robotic radiosurgery system. Each patient had a single tumor with a median volume of 6.43 cm 3 (range, 0.33–29.72 cm 3 ). The IRIS-based plan quality and MLC-based plan quality were evaluated by comparing the dosimetric indices, taking into account the planning target volume (PTV) coverage, the conformity index (CI), and the dose gradient (R 10% and R 50% ). The dose–response SCR with sarcoma/carcinoma induction was calculated using the concept of the organ equivalent dose (OED). Analyses of sarcoma/carcinoma induction were performed using excess absolute risk (EAR) and various OED models of dose–response type/lifetime attributable risk (LAR). Moreover, analyses were performed using the BEIR VII model. PTV coverage using both IRIS-based plans and MLC-based plans was identical, although the CI values obtained using the MLC-based plans showed greater statistical significance. In comparison with the IRIS-based plans, the MLC-based plans showed better dose falloff for R 10% and R 50% evaluation. The estimated difference between Schneider’s model and BEIR VII in linear-no-threshold (Lnt) cumulative EAR was about twofold. The average values of LAR/EAR for carcinoma, for the IRIS-based plans, were 25% higher than those for the MLC-based plans using four SCR models; for sarcoma, they were 15% better in Schneider’s SCR models. MLC-based plans showed slightly better conformity, dose gradients, and SCR reduction. There was a slight increase in SCR with IRIS-based plans in comparison with MLC-based plans. EAR analyses did not show any significant difference between PTV and brainstem analyses, regardless of the tumor volume. Nevertheless, an increase in target volume led to an increase in the probability of SCR. EAR showed statistically significant differences in the soft tissue according to tumor volume (1–10 cc and ≥10 cc).

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“…1). 1, 3 The latter, allowing for the radiation field size to be varied during treatment delivery, has the potential to decrease the peripheral dose compared to fixed collimators4 and to reduce treatment time 3. A CyberKnife system, the first of its kind in Australia, was recently installed at the Sir Charles Gairdner Hospital (SCGH), Nedlands, WA, with promising early clinical results 5…”

Section: Introductionmentioning

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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CyberKnife® M6™: Peripheral dose evaluation for brain treatments

Cited by 6 publications

References 28 publications

A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

Plan Quality and Secondary Cancer Risk Assessment in Patients with Benign Intracranial Lesions after Radiosurgery using the CyberKnife M6 Robotic Radiosurgery System

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

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CyberKnife® M6™: Peripheral dose evaluation for brain treatments

Cited by 6 publications

References 28 publications

A new Monte Carlo model of a Cyberknife® system for the precise determination of out-of-field doses

A new Monte Carlo model of a Cyberknife® system for the precise determination of out-of-field doses

Plan Quality and Secondary Cancer Risk Assessment in Patients with Benign Intracranial Lesions after Radiosurgery using the CyberKnife M6 Robotic Radiosurgery System

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

Contact Info

Product

Resources

About

A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

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