skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SU-E-T-31: A Fast Finite Size Pencil Beam (FSPB) Convolution Algorithm for a New Co-60 Arc Therapy Machine

Abstract

Purpose: Present a fast Finite Size Pencil Beam (FSPB) convolution algorithm for a new Co-60 arc therapy machine. The FSPB algorithm accounts for (i) strong angular divergence (short SAD), (ii) heterogeneity effect for primary attenuation, and (iii) source energy spectrum. Methods: The FSPB algorithm is based on a 0.5×0.5-cm2 dose kernel calculated using the GEPTS (Gamma Electron and Positron Transport System) Monte Carlo code. The dose kernel is tabulated using a thin XYZ mesh (0.1 mm steps in lateral directions) for radius less than 1 cm and using an RZ mesh (with varying steps) for larger radial distance. To account for SSD effect, 11 dose kernels with SSDs varying between 30 cm to 80 cm are calculated. Maynord factor and “lateral stretching” are applied to account for differences between closest and actual SSD. Appropriate rotations and second order interpolation are used to calculate the dose from a given beamlet to a point. Results: Accuracy: Dose distributions in water with 80 cm SSD are calculated using the new FSPB convolution algorithm and full Monte Carlo simulation (gold standard). Figs 1–4 show excellent agreements between FSPB and Monte Carlo calculations for different field sizes and at different depths. The dose distribution formore » a prostate case is calculated using FSPB (Fig.5). Sixty conformal beams with rectum blocking are assumed. Figs 6–8 show the comparison with Monte Carlo simulation based on the same beam apertures. The excellent agreement demonstrates the accuracy of the new algorithm in handling SSD variation, oblique incidence, and scatter contribution.Speed: The FSPB convolution algorithm calculates 28 million dose points per second using a single 2.2-GHz CPU. The present algorithm is seven times faster than a similar algorithm from Gu et al. (Phys. Med. Biol. 54, 2009, 6287–6297). Conclusion: A fast and accurate FSPB convolution algorithm was developed and benchmarked.« less

Authors:
; ;  [1]
  1. Fox Chase Cancer Center, Philadelphia, PA (United States)
Publication Date:
OSTI Identifier:
22545165
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; ALGORITHMS; BEAMS; COBALT 60; COMPUTERIZED SIMULATION; ENERGY SPECTRA; KERNELS; MONTE CARLO METHOD; PROSTATE; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY; RECTUM

Citation Formats

Chibani, O, Eldib, A, and Ma, C. SU-E-T-31: A Fast Finite Size Pencil Beam (FSPB) Convolution Algorithm for a New Co-60 Arc Therapy Machine. United States: N. p., 2015. Web. doi:10.1118/1.4924392.
Chibani, O, Eldib, A, & Ma, C. SU-E-T-31: A Fast Finite Size Pencil Beam (FSPB) Convolution Algorithm for a New Co-60 Arc Therapy Machine. United States. doi:10.1118/1.4924392.
Chibani, O, Eldib, A, and Ma, C. Mon . "SU-E-T-31: A Fast Finite Size Pencil Beam (FSPB) Convolution Algorithm for a New Co-60 Arc Therapy Machine". United States. doi:10.1118/1.4924392.
@article{osti_22545165,
title = {SU-E-T-31: A Fast Finite Size Pencil Beam (FSPB) Convolution Algorithm for a New Co-60 Arc Therapy Machine},
author = {Chibani, O and Eldib, A and Ma, C},
abstractNote = {Purpose: Present a fast Finite Size Pencil Beam (FSPB) convolution algorithm for a new Co-60 arc therapy machine. The FSPB algorithm accounts for (i) strong angular divergence (short SAD), (ii) heterogeneity effect for primary attenuation, and (iii) source energy spectrum. Methods: The FSPB algorithm is based on a 0.5×0.5-cm2 dose kernel calculated using the GEPTS (Gamma Electron and Positron Transport System) Monte Carlo code. The dose kernel is tabulated using a thin XYZ mesh (0.1 mm steps in lateral directions) for radius less than 1 cm and using an RZ mesh (with varying steps) for larger radial distance. To account for SSD effect, 11 dose kernels with SSDs varying between 30 cm to 80 cm are calculated. Maynord factor and “lateral stretching” are applied to account for differences between closest and actual SSD. Appropriate rotations and second order interpolation are used to calculate the dose from a given beamlet to a point. Results: Accuracy: Dose distributions in water with 80 cm SSD are calculated using the new FSPB convolution algorithm and full Monte Carlo simulation (gold standard). Figs 1–4 show excellent agreements between FSPB and Monte Carlo calculations for different field sizes and at different depths. The dose distribution for a prostate case is calculated using FSPB (Fig.5). Sixty conformal beams with rectum blocking are assumed. Figs 6–8 show the comparison with Monte Carlo simulation based on the same beam apertures. The excellent agreement demonstrates the accuracy of the new algorithm in handling SSD variation, oblique incidence, and scatter contribution.Speed: The FSPB convolution algorithm calculates 28 million dose points per second using a single 2.2-GHz CPU. The present algorithm is seven times faster than a similar algorithm from Gu et al. (Phys. Med. Biol. 54, 2009, 6287–6297). Conclusion: A fast and accurate FSPB convolution algorithm was developed and benchmarked.},
doi = {10.1118/1.4924392},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}
  • Purpose: Recent developments in radiation therapy have been focused on applications of charged particles, especially protons. Over the years several dose calculation methods have been proposed in proton therapy. A common characteristic of all these methods is their extensive computational burden. In the current study we present for the first time, to our best knowledge, a GPU-based PBA for proton dose calculations in Matlab. Methods: In the current study we employed an analytical expression for the protons depth dose distribution. The central-axis term is taken from the broad-beam central-axis depth dose in water modified by an inverse square correction whilemore » the distribution of the off-axis term was considered Gaussian. The serial code was implemented in MATLAB and was launched on a desktop with a quad core Intel Xeon X5550 at 2.67GHz with 8 GB of RAM. For the parallelization on the GPU, the parallel computing toolbox was employed and the code was launched on a GTX 770 with Kepler architecture. The performance comparison was established on the speedup factors. Results: The performance of the GPU code was evaluated for three different energies: low (50 MeV), medium (100 MeV) and high (150 MeV). Four square fields were selected for each energy, and the dose calculations were performed with both the serial and parallel codes for a homogeneous water phantom with size 300×300×300 mm3. The resolution of the PBs was set to 1.0 mm. The maximum speedup of ∼127 was achieved for the highest energy and the largest field size. Conclusion: A GPU-based PB algorithm for proton dose calculations in Matlab was presented. A maximum speedup of ∼127 was achieved. Future directions of the current work include extension of our method for dose calculation in heterogeneous phantoms.« less
  • Purpose: The present study aimed to investigate the dosimetric impacts of the anisotropic analytic algorithm (AAA) and the Acuros XB (AXB) plan for lung stereotactic ablative radiation therapy using flattening filter-free (FFF) beam. We retrospectively analyzed 10 patients. Methods: We retrospectively analyzed 10 patients. The dosimetric parameters for the target and organs at risk (OARs) from the treatment plans calculated with these dose calculation algorithms were compared. The technical parameters, such as the computation times and the total monitor units (MUs), were also evaluated. Results: A comparison of DVHs from AXB and AAA showed that the AXB plan produced amore » high maximum PTV dose by average 4.40% with a statistical significance but slightly lower mean PTV dose by average 5.20% compared to the AAA plans. The maximum dose to the lung was slightly higher in the AXB compared to the AAA. For both algorithms, the values of V5, V10 and V20 for ipsilateral lung were higher in the AXB plan more than those of AAA. However, these parameters for contralateral lung were comparable. The differences of maximum dose for the spinal cord and heart were also small. The computation time of AXB was found fast with the relative difference of 13.7% than those of AAA. The average of monitor units (MUs) for all patients was higher in AXB plans than in the AAA plans. These results indicated that the difference between AXB and AAA are large in heterogeneous region with low density. Conclusion: The AXB provided the advantages such as the accuracy of calculations and the reduction of the computation time in lung stereotactic ablative radiotherapy (SABR) with using FFF beam, especially for VMAT planning. In dose calculation with the media of different density, therefore, the careful attention should be taken regarding the impacts of different heterogeneity correction algorithms. The authors report no conflicts of interest.« less
  • Purpose: To provide a wide range of dose output for intensity modulation purposes while minimizing the beam penumbra for a new rotating cobalt therapy system. The highest dose rate needs to be maximized as well. Methods: The GEPTS Monte Carlo system is used to calculate the dose distribution from each tested Co-60 head for a wide range of field sizes (1×1 to 40×40 cm2). This includes the transport of photons (and secondary electrons) from the source through the collimation system (primary collimator, Y and × jaws, and MLCs) and finally in the water phantom. Photon transport includes Compton scattering (withmore » electron binding effect), Rayleigh scattering, Photoelectric effect (with detailed simulation of fluorescence x-rays). Calculations are done for different system designs to reduce geometric penumbra and provide dose output modulation. Results: Taking into account different clinical requirements, the choice of a movable head (SAD = 70 to 80 cm) is made. The 120-leaf MLC (6-cm thick) entrance is at 32 cm from the bottom of the source (to reduce penumbra while allowing larger patient clearance). Three system designs (refereed here as S1–3) were simulated with different effective source sizes (2mm, 10mm and 17mm diameter). The effective point source is at mid-height of the 25-mm-long source. Using a 12000-Ci source, the designed Co-60 head can deliver a wide range of dose outputs (0.5 − 4 Gy/mn). A dose output of 2.2 Gy/mn can be delivered for a 10cm × 10cm field size with 1-cm penumbra using a 10mm effective source. Conclusion: A new 60Co-based VMAT machine is designed to meet different clinical requirements in term of dose output and beam penumbra. Outcomes from this study can be used for the design of 60Co machines for which a renewed interest is seen.« less
  • Purpose: Rotational proton radiotherapy would be an interesting treatment modality if it proves to produce dose distributions that conform to the target as well or better than currently available treatment modalities, while reducing the dose to the surrounding organs at risk. A treatment planning study is presented, showing how this objective can be achieved using a single or small number of scanned mono-energetic pencil beams delivered while the proton gantry rotates at the same time that they may deliver faster and more biologically effective treatments than current proton modalities.Methods Proton treatment using single- (SFO) and multi-field optimized (MFO) PBS plansmore » are compared with PMAT plans in phantoms of different shape and uniformity as well as on a brain case. The method followed in ECLIPSE to produce PMAT plans is presented and the feasibility is discussed. Results Table 1 shows that the conformity and uniformity of the PMAT plans is of similar order than those of the SFO and MFO plans. However, in the brain case, the DVHs shown in Figure 1 indicate a significant reduction of the dose to the OARs when PMAT is used. Similarly, the use of PMAT increases the LET in the treatment area, which could translate into a more biologically effective treatment.Conclusions PMAT could provide dose distributions as conformal as current PBS plans but could also offer faster beam delivery and more biologically effective proton plans.« less
  • Purpose: To evaluate planning methods for anal canal cancer and compare the results of 9-field Intensity Modulated Radiotherapy (IMRT), Volumetric Modulated Arc Therapy (Varian, RapidArc), and Proton Pencil Beam Scanning (PBS). Methods: We generated plans with IMRT, RapidArc (RA) and PBS for twenty patients for both initial phase including nodes and cone down phase of treatment using Eclipe (Varian). We evaluated the advantage of each technique for each phase. RA plans used 2 to 4 arcs and various collimator orientations. PBS used two posterior oblique fields. We evaluated the plans comparing dose volume histogram (DVH), locations of hot spots, andmore » PTV dose conformity. Results: Due to complex shape of target, for RA plans, multiple arcs (>2) are required to achieve optimal PTV conformity. When the PTV exceeds 15 cm in the superior-inferior direction, limitations of deliverability start to dominate. The PTV should be divided into a superior and an inferior structure. The optimization is performed with fixed jaws for each structure and collimator set to 90 degrees for the inferior PTV. Proton PBS plans show little advantage in small bowel sparing when treating the nodes. However, PBS plan reduces volumetric dose to the bladder at the cost of higher doses to the perineal skin. IMRT plans provide good target conformity, but they generate hot spots outside of the target volume. Conclusion: When using one planning technique for entire course of treatment, Multiple arc (>2) RA plans are better as compared to IMRT and PBS plans. When combining techniques, RA for the initial phase in combination with PBS for the cone down phase results in the most optimal plans.« less