Comparison of dose distributions calculated by the cyberknife Monte Carlo and ray tracing algorithms for lung tumors: a phantom study

Koksal, Canan; Akbas, Ugur; Okutan, Murat; Demir, Bayram; Sarpün, İ̇smail Hakkı

doi:10.1051/epjconf/201510003003

Cited by 4 publications

(3 citation statements)

References 6 publications

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“…TPR, and output factor to calculate the dose kernel and the effective path length to correct for heterogeneities. 29 The second method is Monte Carlo which adopts a virtual source (phase space file of the linac head) to calculate the dose. 29 Three plans of uniform coverage were created using the RTrac method.…”

Section: G | Field Size Factor Measurementmentioning

confidence: 99%

Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector

Alhujaili

Biasi

Alzorkany

et al. 2018

J Applied Clin Med Phys

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PurposeThe aim of this work was to evaluate the use of an angularly independent silicon detector (edgeless diodes) developed for dosimetry in megavoltage radiotherapy for Cyberknife in a phantom and for patient quality assurance (QA).MethodThe characterization of the edgeless diodes has been performed on Cyberknife with fixed and IRIS collimators. The edgeless diode probes were tested in terms of basic QA parameters such as measurements of tissue‐phantom ratio (TPR), output factor and off‐axis ratio. The measurements were performed in both water and water‐equivalent phantoms. In addition, three patient‐specific plans have been delivered to a lung phantom with and without motion and dose measurements have been performed to verify the ability of the diodes to work as patient‐specific QA devices. The data obtained by the edgeless diodes have been compared to PTW 60016, SN edge, PinPoint ionization chamber, Gafchromic EBT3 film, and treatment planning system (TPS).ResultsThe TPR measurement performed by the edgeless diodes show agreement within 2.2% with data obtained with PTW 60016 diode for all the field sizes. Output factor agrees within 2.6% with that measured by SN EDGE diodes corrected for their field size dependence. The beam profiles’ measurements of edgeless diodes match SN EDGE diodes with a measured full width half maximum (FWHM) within 2.3% and penumbra widths within 0.148 mm. Patient‐specific QA measurements demonstrate an agreement within 4.72% in comparison with TPS.ConclusionThe edgeless diodes have been proved to be an excellent candidate for machine and patient QA for Cyberknife reproducing commercial dosimetry device measurements without need of angular dependence corrections. However, further investigation is required to evaluate the effect of their dose rate dependence on complex brain cancer dose verification.

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Section: G | Field Size Factor Measurementmentioning

confidence: 99%

Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector

Alhujaili

Biasi

Alzorkany

et al. 2018

J Applied Clin Med Phys

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“…The Ray‐tracing algorithm calculates doses using only density correction of the primary photon components obtained from measured data such as OCR, TPR, and OPF. This calculation method does not consider the contribution of the scattered radiation component along the off‐axis direction . In contrast, the FSPB algorithm considers this in the calculation.…”

Section: Discussionmentioning

confidence: 99%

“…This calculation method does not consider the contribution of the scattered radiation component along the off-axis direction. [30][31][32][33] In contrast, the FSPB algorithm considers this in the calculation. Therefore, compared with the Ray-tracing algorithm, the dose error of the FSPB algorithm was considered to be smaller, and the results are confirmed in this study.…”

Section: Discussionmentioning

confidence: 99%

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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Film‐based dose validation of Monte Carlo algorithm for Cyberknife system with a CIRS thorax phantom

Pan

Yang

et al. 2018

J Applied Clin Med Phys

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Monte Carlo (MC) simulation, as the most accurate dose calculation algorithm, is available in the MultiPlan treatment planning system for Cyberknife. The main purpose of this work was to perform experiments to thoroughly investigate the accuracy of the MC dose calculation algorithm. Besides the basic MC beam commissioning, two test scenarios were designed. First, single beam tests were performed with a solid water phantom to verify the MC source model in simple geometry. Then, a lung treatment plan on a CIRS thorax phantom was created to mimic the clinical patient treatment. The plan was optimized and calculated using ray tracing (RT) algorithm and then recalculated using MC algorithm. Measurements were performed in both a homogeneous phantom and a heterogeneous phantom (CIRS). Ion‐chamber and radiochromic film were used to obtain absolute point dose and dose distributions. Ion‐chamber results showed that the differences between measured and MC calculated dose were within 3% for all tests. On the film measurements, MC calculation results showed good agreements with the measured dose for all single beam tests. As for the lung case, the gamma passing rate between measured and MC calculated dose was 98.31% and 97.28% for homogeneous and heterogeneous situation, respectively, using 3%/2 mm criteria. However, RT algorithm failed with the passing rate of 79.25% (3%/2 mm) for heterogeneous situation. These results demonstrated that MC dose calculation algorithm in the Multiplan system is accurate enough for patient dose calculation. It is strongly recommended to use MC algorithm in heterogeneous media.

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Comparison of dose distributions calculated by the cyberknife Monte Carlo and ray tracing algorithms for lung tumors: a phantom study

Cited by 4 publications

References 6 publications

Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector

Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector

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

Film‐based dose validation of Monte Carlo algorithm for Cyberknife system with a CIRS thorax phantom

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