Novel Monte Carlo dose calculation algorithm for robotic radiosurgery with multi leaf collimator: Dosimetric evaluation

Heidorn, Sarah-Charlotta; Kilby, W.; Fürweger, Christoph

doi:10.1016/j.ejmp.2018.10.011

Cited by 11 publications

(20 citation statements)

References 27 publications

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“…The underlying reason is that the FSPB algorithm is unable to reproduce the physical effects causing the larger mean free paths of the secondary electrons in the low-density region and the lateral disequilibrium of the secondary electrons from the same region, because this algorithm only performs density correction for the contribution of the primary photon component. [8][9][10][11]17 In contrast, the results for the FSPB+ and MC algorithms agreed with the measured doses. The FSPB+ algorithm performs the lateral scaling correction that adjusts the model parameters for the dose deposition kernel based on the local density through which the beam passes.…”

Section: Discussionmentioning

confidence: 64%

“…For the dose distributions measured by the films in the clinical evaluations, the doses calculated by the FSPB algorithm were extreme high at the boundary regions of the tumor edge, compared with the measured doses in this study. The underlying reason is that the FSPB algorithm is unable to reproduce the physical effects causing the larger mean free paths of the secondary electrons in the low‐density region and the lateral disequilibrium of the secondary electrons from the same region, because this algorithm only performs density correction for the contribution of the primary photon component . In contrast, the results for the FSPB+ and MC algorithms agreed with the measured doses.…”

Section: Discussionmentioning

confidence: 90%

“…This correction is considered to have substantially contributed to the agreement between the measured and FSPB+ algorithm calculated doses in the lung motion phantom. Moreover, the MC algorithm can model the mean free paths of the secondary electrons in the low‐density regions and at the boundary between regions of different densities, more accurately . These physical characteristics of the MC algorithm also contributed to the agreement between the calculated and measured dose distributions.…”

Section: Discussionmentioning

confidence: 96%

“…In a previous study, Heidorn et al . evaluated the accuracy of the dose calculation in the PDDs in inhomogeneous phantom geometry for Precision TPS . They reported that the gamma passing rates (criterion: 2%/1 mm) between the PDDs measured in the films and calculated by the MC algorithm were about 90% or more.…”

Section: Discussionmentioning

confidence: 99%

“…[14][15][16] The implementation of the FSPB+ and MC algorithms in the MLC-based treatment planning for CK can be expected to improve the accuracy of the calculated dose, especially for inhomogeneous regions. Although the basic dosimetric evaluations of the single beams by the MC algorithm implemented in Precision TPS have been reported by Heidorn et al, 17 clinical multifield irradiations with the FSPB+ and MC algorithms have not been evaluated thus far.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

et al. 2020

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Purpose In the previous treatment planning system (TPS) for CyberKnife (CK), multileaf collimator (MLC)‐based treatment plans could be created only by using the finite‐size pencil beam (FSPB) algorithm. Recently, a new TPS, including the FSPB with lateral scaling option (FSPB+) and Monte Carlo (MC) algorithms, was developed. In this study, we performed basic and clinical end‐to‐end evaluations for MLC‐based CK tumor‐tracking radiotherapy using the MC, FSPB+, and FSPB. Methods Water‐ and lung‐equivalent slab phantoms were combined to obtain the percentage depth dose (PDD) and off‐center ratio (OCR). The CK M6 system and Precision TPS were employed, and PDDs and OCRs calculated by the MC, FSPB+, and FSPB were compared with the measured doses obtained for 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields. A lung motion phantom was used for clinical evaluation and MLC‐based treatment plans were created using the MC. The doses were subsequently recalculated using the FSPB+ and FSPB, while maintaining the irradiation parameters. The calculated doses were compared with the doses measured using a microchamber (for target doses) or a radiochromic film (for dose profiles). The dose volume histogram (DVH) indices were compared for all plans. Results In homogeneous and inhomogeneous phantom geometries, the PDDs calculated by the MC and FSPB+ agreed with the measurements within ±2.0% for the region between the surface and a depth of 250 mm, whereas the doses calculated by the FSPB in the lung‐equivalent phantom region were noticeably higher than the measurements, and the maximum dose differences were 6.1% and 4.4% for the 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields, respectively. The maximum distance to agreement values of the MC, FSPB+, and FSPB at the penumbra regions of OCRs were 1.0, 0.6, and 1.1 mm, respectively, but the best agreement was obtained between the MC‐calculated curve and measurements at the boundary of the water‐ and lung‐equivalent slabs, compared with those of the FSPB+ and FSPB. For clinical evaluations using the lung motion phantom, under the static motion condition, the dose errors measured by the microchamber were −1.0%, −1.9%, and 8.8% for MC, FSPB+, and FSPB, respectively; their gamma pass rates for the 3%/2 mm criterion comparing to film measurement were 98.4%, 87.6%, and 31.4% respectively. Under respiratory motion conditions, there was no noticeable decline in the gamma pass rates. In the DVH indices, for most of the gross tumor volume and planning target volume, significant differences were observed between the MC and FSPB, and between the FSPB+ and FSPB. Furthermore, significant differences were observed for lung Dmean, V15 Gy, and V20 Gy between the MC, FSPB+, and FSPB. Conclusions The results indicate that the doses calculated using the MC and FSPB+ differed remarkably in inhomogeneous regions, compared with the FSPB. Because the MC was the most consistent with the measurements, it is recommended for final dose calculations in inhomogeneous regions such as the lung. Furthermore, the sufficient accurac...

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Section: Discussionmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

et al. 2020

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A novel Monte Carlo (MC) dose model for small MLC fields of the cyberknife^® M6^TM radiosurgery system using the EGSnrc

Neupane

Galanakou

Shang

et al. 2023

J Applied Clin Med Phys

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The multi‐leaf collimator (MLC)‐equipped CyberKnife ® M6 radiosurgery system (CKM6) (Accuray Inc., Sunnyvale, CA) has been increasingly employed for stereotactic radiosurgery (SRS) to treat relatively small lesions. However, achieving an accurate dose distribution in such cases is usually challenging due to the combination of numerous small fields ≤ (30 × 30) mm 2 . In this study, we developed a new Monte Carlo (MC) dose model for the CKM6 system using the EGSnrc to investigate dose variations in the small fields. The dose model was verified for the static MLC fields ranging from (53.8 × 53.9) to (7.6 × 7.7) mm 2 at 800 mm source to axis distance in a water phantom, based on the computed doses of Accuray Precision ® (Accuray Inc.) treatment planning system (TPS). We achieved a statistical uncertainty of ≤4% by simulating 30–50 million incident particles/histories. Then, the treatment plans were created for the same fields in the TPS, and the corresponding measurements were performed with MapCHECK2 (Sun Nuclear Corporation), a standard device for patient‐specific quality assurance (PSQA). Results of the MC simulations, TPS, and MapCHECK2 measurements were inter‐compared. An overall difference in dosimetric parameters such as profiles, tissue maximum ratio (TMR), and output factors (OF) between the MC simulations and the TPS results was found ≤3% for (53.8 × 53.9–15.4 × 15.4) mm 2 MLC fields, and it rose to 4.5% for the smallest (7.6 mm × 7.7 mm) MLC field. The MapCHECK2 results showed a deviation ranging from –1.5% to + 4.5% compared to the TPS results, whereas the deviation was within ±2.5% compared with the MC results. Overall, our MC dose model for the CKM6 system showed better agreement with measurements and it could serve as a secondary dose verification tool for the patient‐specific QA in small fields.

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AAPM task group report 135.B: Quality assurance for robotic radiosurgery

Wang,

Descovich,

Wilcox

et al. 2024

Medical Physics

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AAPM Task Group Report 135.B covers new technology components that have been added to an established radiosurgery platform and updates the components that were not well covered in the previous report. Considering the current state of the platform, this task group (TG) is a combination of a foundational task group to establish the basis for new processes/technology and an educational task group updating guidelines on the established components of the platform. Because the technology discussed in this document has a relatively small user base compared to C‐arm isocentric linacs, the authors chose to emphasize the educational components to assist medical physicists who are new to the technology and have not had the opportunity to receive in‐depth vendor training at the time of reading this report. The TG has developed codes of practice, introduced QA, and developed guidelines which are generally expected to become enduring practice. This report makes prescriptive recommendations as there has not been enough longitudinal experience with some of the new technical components to develop a data‐based risk analysis.

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Novel Monte Carlo dose calculation algorithm for robotic radiosurgery with multi leaf collimator: Dosimetric evaluation

Cited by 11 publications

References 27 publications

Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

A novel Monte Carlo (MC) dose model for small MLC fields of the cyberknife^® M6^TM radiosurgery system using the EGSnrc

AAPM task group report 135.B: Quality assurance for robotic radiosurgery

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Novel Monte Carlo dose calculation algorithm for robotic radiosurgery with multi leaf collimator: Dosimetric evaluation

Cited by 11 publications

References 27 publications

Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

A novel Monte Carlo (MC) dose model for small MLC fields of the cyberknife® M6TM radiosurgery system using the EGSnrc

AAPM task group report 135.B: Quality assurance for robotic radiosurgery

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A novel Monte Carlo (MC) dose model for small MLC fields of the cyberknife^® M6^TM radiosurgery system using the EGSnrc