3D electron dose calculation using a Voxel based Monte Carlo algorithm (VMC)

A new GPU‐based Monte Carlo dose calculation algorithm (GPUMCD), developed by the vendor Elekta for the Monaco treatment planning system (TPS), is capable of modeling dose for both a standard linear accelerator and an Elekta MRI linear accelerator. We have experimentally evaluated this algorithm for a standard Elekta Agility linear accelerator. A beam model was developed in the Monaco TPS (research version 5.09.06) using the commissioned beam data for a 6 MV Agility linac. A heterogeneous phantom representing several scenarios — tumor‐in‐lung, lung, and bone‐in‐tissue — was designed and built. Dose calculations in Monaco were done using both the current clinical Monte Carlo algorithm, XVMC, and the new GPUMCD algorithm. Dose calculations in a Pinnacle TPS were also produced using the collapsed cone convolution (CCC) algorithm with heterogeneity correction. Calculations were compared with the measured doses using an ionization chamber (A1SL) and Gafchromic EBT3 films for 2×2 cm2,5×5 cm2, and 10×2 cm2 field sizes. The percentage depth doses (PDDs) calculated by XVMC and GPUMCD in a homogeneous solid water phantom were within 2%/2 mm of film measurements and within 1% of ion chamber measurements. For the tumor‐in‐lung phantom, the calculated doses were within 2.5%/2.5 mm of film measurements for GPUMCD. For the lung phantom, doses calculated by all of the algorithms were within 3%/3 mm of film measurements, except for the 2×2 cm2 field size where the CCC algorithm underestimated the depth dose by ∼5% in a larger extent of the lung region. For the bone phantom, all of the algorithms were equivalent and calculated dose to within 2%/2 mm of film measurements, except at the interfaces. Both GPUMCD and XVMC showed interface effects, which were more pronounced for GPUMCD and were comparable to film measurements, whereas the CCC algorithm showed these effects poorly.PACS number(s): 87.53.Bn, 87.55.dh, 87.55.km

Section: Introductionmentioning

confidence: 99%

Experimental evaluation of a GPU‐based Monte Carlo dose calculation algorithm in the Monaco treatment planning system

Paudel

Kim

Sarfehnia

et al. 2016

“…2b) may cause the electrons to terminate their tracks and deposit their energies that would be otherwise carried away from the spot. On the other hand, the approximate efficiency improvement techniques implemented in the high‐energy inelastic interaction calculation for electron transport, which may cause substantial difference between absorbed dose to variable density water in the MultiPlan Monte Carlo algorithm and absorbed dose to medium, (25) were expected to exaggerate errors of the dose calculation results given the significant distortion of the high‐density metal markers in the CT images. The errors of DIRs and dose calculations due to image artifacts can be clearly visualized by comparing the dose distribution calculated on static geometry (Fig.…”

Section: Discussionmentioning

confidence: 99%

Accuracy and sensitivity of four‐dimensional dose calculation to systematic motion variability in stereotatic body radiotherapy (SBRT) for lung cancer

Chan

Kwong

et al. 2012

The dynamic movement of radiation beam in real‐time tumor tracking may cause overdosing to critical organs surrounding the target. The primary objective of this study was to verify the accuracy of the 4D planning module incorporated in CyberKnife treatment planning system. The secondary objective was to evaluate the error that may occur in the case of a systematic change of motion pattern. Measurements were made using a rigid thorax phantom. Target motion was simulated with two waveforms (sin and cos4) of different amplitude and frequency. Inversely optimized dose distributions were calculated in the CyberKnife treatment planning system using the 4D Monte Carlo dose calculation algorithm. Each plan was delivered to the phantom assuming (1) reproducible target motion, and (2) systematic change of target motion pattern. The accuracy of 4D dose calculation algorithm was assessed using GAFCHROMIC EBT2 films based on 5%/3 mm γ criteria. Treatment plans were considered acceptable if the percentage of pixels passing the 5%/3 mm γ criteria was greater than 90%. The mean percentages of pixels passing were 95% for the target and 91% for the static off‐target structure, respectively, with reproducible target motion. When systematic changes of the motion pattern were introduced during treatment delivery, the mean percentages of pixels passing decreased significantly in the off‐target films (48%; p < 0.05), but did not change significantly in the target films (92%; p=0.324) compared to results of reproducible target motion. These results suggest that the accuracy of 4D dose calculation, particularly in off‐target stationary structure, is strongly tied to the reproducibility of target motion and that the solutions of 4D planning do not reflect the clinical nature of nonreproducible target motion generally.PACS numbers: 87.53.Ly, 87.55.km

“…Treatment was planned in the Nucletron Oncentra MasterPlan, version 4.3 TPS using a single electron beam of 6 or 9 MeV. The dose distribution was calculated using the Voxel Monte Carlo calculation algorithm32 and at least 50,000 number of histories/cm 2 , which equals 50,000 incident electrons/cm 2 . Using computed tomography (CT) scans with 2 mm slice thickness, a bolus individual to each patient was designed in the TPS (reference bolus), which was then produced using a 3D printer — a 3D‐printed bolus.…”

Section: Methodsmentioning

confidence: 99%

Utilization of a 3D printer to fabricate boluses used for electron therapy of skin lesions of the eye canthi

Łukowiak

Jezierska

Boehlke

et al. 2016

This work describes the use of 3D printing technology to create individualized boluses for patients treated with electron beam therapy for skin lesions of the eye canthi. It aimed to demonstrate the effectiveness of 3D‐printed over manually fabricated paraffin boluses. The study involved 11 patients for whom the construction of individual boluses were required. CT scans of the fabricated 3D‐printed boluses and paraffin boluses were acquired and superimposed onto patient CT scans to compare their fitting, bolus homogeneity, and underlying dose distribution. To quantify the level of matching, multiple metrics were utilized. Matching Level Index (ML) values ranged from 0 to 100%, where 100% indicated a perfect fit between the reference bolus (planned in treatment planning system) and 3D‐printed and paraffin bolus. The average ML (± 1 SD) of the 3D‐printed boluses was 95.1 ± 2.1%, compared to 46.0 ± 10.1% for the manually fabricated paraffin bolus. Correspondingly, mean doses were closer to the prescribed doses, and dose spreads were less for the dose distributions from the 3D‐printed boluses, as compared to those for the manually fabricated paraffin boluses. It was concluded that 3D‐printing technology is a viable method for fabricating boluses for small eye lesions and provides boluses superior to our boluses manually fabricated from paraffin sheets.