Dose calculation models for proton treatment planning using a dynamic beam delivery system: an attempt to include density heterogeneity effects in the analytical dose calculation

Schaffner, Barbara; Pedroni, E.; Lomax, Anthony

doi:10.1088/0031-9155/44/1/004

Cited by 235 publications

(277 citation statements)

References 16 publications

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“…The same source model derived in previous sections is directly implemented into MCsquare. The analytical algorithm in TPS used in this work was Eclipse verison 13.7 (Varian Medical Systems, Palo Alto, CA) with the proton convolution superposition (PCS) dose algorithm,40 which is a fluence‐dose calculation technique that calculates dose by convolving the proton fluence with a dose kernel 41. One representative locally advanced liver cancer case and one complex locally advanced lung case were simulated with approximately the same number of ~2 × 10 7 protons per field for each of the two MC algorithms, as well calculated in the commercial TPS.…”

Section: Methodsmentioning

confidence: 99%

Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Huang

Kang

Souris

et al. 2018

J Applied Clin Med Phys

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Monte Carlo (MC)‐based dose calculations are generally superior to analytical dose calculations (ADC) in modeling the dose distribution for proton pencil beam scanning (PBS) treatments. The purpose of this paper is to present a methodology for commissioning and validating an accurate MC code for PBS utilizing a parameterized source model, including an implementation of a range shifter, that can independently check the ADC in commercial treatment planning system (TPS) and fast Monte Carlo dose calculation in opensource platform (MCsquare). The source model parameters (including beam size, angular divergence and energy spread) and protons per MU were extracted and tuned at the nozzle exit by comparing Tool for Particle Simulation (TOPAS) simulations with a series of commissioning measurements using scintillation screen/CCD camera detector and ionization chambers. The range shifter was simulated as an independent object with geometric and material information. The MC calculation platform was validated through comprehensive measurements of single spots, field size factors (FSF) and three‐dimensional dose distributions of spread‐out Bragg peaks (SOBPs), both without and with the range shifter. Differences in field size factors and absolute output at various depths of SOBPs between measurement and simulation were within 2.2%, with and without a range shifter, indicating an accurate source model. TOPAS was also validated against anthropomorphic lung phantom measurements. Comparison of dose distributions and DVHs for representative liver and lung cases between independent MC and analytical dose calculations from a commercial TPS further highlights the limitations of the ADC in situations of highly heterogeneous geometries. The fast MC platform has been implemented within our clinical practice to provide additional independent dose validation/QA of the commercial ADC for patient plans. Using the independent MC, we can more efficiently commission ADC by reducing the amount of measured data required for low dose “halo” modeling, especially when a range shifter is employed.

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Section: Methodsmentioning

confidence: 99%

Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Huang

Kang

Souris

et al. 2018

J Applied Clin Med Phys

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“…In addition, dense bony structures, such as the femur and FH, in the beam path can also cause uncertainties in dose distributions because the Bragg peak becomes degraded [19]. This degradation, in turn, affects the final dose distribution [20]. Hence, depending on the type of immobilization device used, changes in daily patient setup during the course of proton radiotherapy could introduce varying amounts of bone in the treatment field due to FH rotation.…”

Section: A D Melancon Et Almentioning

confidence: 99%

Patient-Specific and Generic Immobilization Devices for Prostate Radiotherapy

Melancon¹,

Kudchadker²,

Amos³

et al. 2013

IJMPCERO

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The purpose of our study was to compare interfractional bony setup variations in pelvic anatomy with two immobilization devices, the patient-specific Vac-Lok and the generic Dual Leg Positioner system (both Civco Medical Solutions, Kalona, IA), for bilateral proton radiotherapy of the prostate. Two groups of 10 patients were studied. Computed tomography (CT) was performed three times a week, yielding 233 CT image sets for the vacuum system group and 252 for the other group. The translational shifts of the pelvic bone and prostate and rotation of the upper femurs of the femoral heads with respect to the simulation CT images were analyzed. Along the anterior-posterior and lateral axes, mean and systematic translational variations of the pelvic bone and prostate, relative to skin fiducials, were significantly lower in the Vac-Lok group (all p < 0.01) than in the Dual Leg Positioner group. Abduction of the upper femur, the dominant rotation, had random rotational variations of 1.9˚ and 2.0˚ and systematic rotations of 3.1˚ and 2.9˚ for the vacuum and generic system groups, respectively. Femoral abduction was highly correlated with anterior prostate displacement for both femurs in both groups (p < 0.01). We conclude that image guidance may be needed to correct systematic translation introduced during simulation CT, particularly with the generic immobilization system. High degrees of femoral rotation may introduce prostate translation and distal misalignment of lateral proton beams with the prostate.

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“…A number of facilities begin to apply the PBS technique to cancer treatment in moving organs like lung and liver by using a repainting technique and a gating technique 5 , 6 . Currently, a treatment planning system (TPS) for the PBS uses an analytical dose calculation method using a pencil beam algorithm (PBA) for proton therapy 7 , 8 . Although this algorithm allows short computation time and is suitable for dose calculation in homogeneous or moderately inhomogeneous media, the accuracy limitation appears in certain clinical sites with large density heterogeneity.…”

Section: Introductionmentioning

confidence: 99%

“…One of such faster FMC codes for TPS in proton therapy, named VMCpro, was reported to be 35 times faster than the general purpose FMC code GEANT4 for simulations in a phantom with large inhomogeneities (10) . The calculation time is approximately 30 to 75 times longer than that by the PBA with an original spot decomposed into 121 subspots 8 , 10 , 11 . Therefore, further reduction of calculation time is desired.…”

Section: Introductionmentioning

confidence: 99%

Application of dose kernel calculation using a simplified Monte Carlo method to treatment plan for scanned proton beams

Mizutani

Takada

Kohno

et al. 2016

J Applied Clin Med Phys

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Full Monte Carlo (FMC) calculation of dose distribution has been recognized to have superior accuracy, compared with the pencil beam algorithm (PBA). However, since the FMC methods require long calculation time, it is difficult to apply them to routine treatment planning at present. In order to improve the situation, a simplified Monte Carlo (SMC) method has been introduced to the dose kernel calculation applicable to dose optimization procedure for the proton pencil beam scanning. We have evaluated accuracy of the SMC calculation by comparing a result of the dose kernel calculation using the SMC method with that using the FMC method in an inhomogeneous phantom. The dose distribution obtained by the SMC method was in good agreement with that obtained by the FMC method. To assess the usefulness of SMC calculation in clinical situations, we have compared results of the dose calculation using the SMC with those using the PBA method for three clinical cases of tumor treatment. The dose distributions calculated with the PBA dose kernels appear to be homogeneous in the planning target volumes (PTVs). In practice, the dose distributions calculated with the SMC dose kernels with the spot weights optimized with the PBA method show largely inhomogeneous dose distributions in the PTVs, while those with the spot weights optimized with the SMC method have moderately homogeneous distributions in the PTVs. Calculation using the SMC method is faster than that using the GEANT4 by three orders of magnitude. In addition, the graphic processing unit (GPU) boosts the calculation speed by 13 times for the treatment planning using the SMC method. Thence, the SMC method will be applicable to routine clinical treatment planning for reproduction of the complex dose distribution more accurately than the PBA method in a reasonably short time by use of the GPU‐based calculation engine.PACS number(s): 87.55.Gh

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Dose calculation models for proton treatment planning using a dynamic beam delivery system: an attempt to include density heterogeneity effects in the analytical dose calculation

Cited by 235 publications

References 16 publications

Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Patient-Specific and Generic Immobilization Devices for Prostate Radiotherapy

Application of dose kernel calculation using a simplified Monte Carlo method to treatment plan for scanned proton beams

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