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H. Wan Chan Tseung

Publications and source records attributed to H. Wan Chan Tseung.

8 recordsLinked to original sources
arXiv2018

A Monte-Carlo-based and GPU-accelerated 4D-dose calculator for a pencil-beam scanning proton therapy system

Purpose: The presence of respiratory motion during radiation treatment leads to degradation of the expected dose distribution, both for target coverage and healthy-tissue sparing, particularly for techniques like pencil-beam scanning proton therapy which have dynamic delivery systems. While tools exist to estimate this degraded four-dimensional (4D) dose, they typically have one or more deficiencies such as ... Methods: To quickly compute the 4D-dose, the three main tasks of the calculator were run on graphics processing units (GPUs). These tasks were: simulating the delivery of the plan using measured delivery parameters to distribute the plan amongst 4DCT phases characterizing the patient breathing, using an in-house Monte Carlo simulation (MC) dose calculator to determine the dose delivered to each breathing phase, and accumulating the doses from the various breathing phases onto a single phase for evaluation. The accumulation was performed by individually transferring the energy and mass of dose-grid subvoxels, a technique models the transfer of dose in a more physically realistic manner. The calculator was run ... Results: 4D doses were successfully computed for the three test cases with computation times ranging from 4-6 min on a server with eight NVIDIA Titan X graphics cards; the most time-consuming component was the MC dose engine. The subvoxel-based dose-accumulation technique produced stable 4D-dose distributions at subvoxel scales of 0.5-1.0 mm without impairing the total computation time. The uncertainties in the beam-delivery simulation ... Conclusions: A MC-based and GPU-accelerated 4D-dose calculator was developed to estimate the effects of respiratory motion on pencil-beam scanning proton therapy treatments. The calculator can currently be used ...

physics.med-ph↗
arXiv2016

Clinically applicable Monte Carlo-based biological dose optimization for the treatment of head and neck cancers with spot-scanning proton therapy

Purpose: To demonstrate the feasibility of fast Monte Carlo (MC) based inverse biological planning for the treatment of head and neck tumors in spot-scanning proton therapy. Methods: Recently, a fast and accurate Graphics Processor Unit (GPU)-based MC simulation of proton transport was developed and used as the dose calculation engine in a GPU-accelerated IMPT optimizer. Besides dose, the dose-averaged linear energy transfer (LETd) can be simultaneously scored, which makes biological dose (BD) optimization possible. To convert from LETd to BD, a linear relation was assumed. Using this novel optimizer, inverse biological planning was applied to 4 patients: 2 small and 1 large thyroid tumor targets, and 1 glioma case. To create these plans, constraints were placed to maintain the physical dose (PD) within 1.25 times the prescription while maximizing target BD. For comparison, conventional IMRT and IMPT plans were created for each case in Eclipse (Varian, Inc). The same critical structure PD constraints were used for the IMRT, IMPT and bio-optimized plans. The BD for the IMPT plans were obtained through MC re-calculations. Results: Compared to standard IMPT, the bio-optimal plans for patients with small tumor targets displayed a BD escalation that was around twice the PD increase. Dose sparing to critical structures was improved compared to both IMRT and IMPT. No significant BD increase could be achieved for the large thyroid case, and when the presence of critical structures mitigated the contribution of additional fields. The calculation of the bio-optimized plans can be completed in a clinically viable time (<30 minutes) on a 24-GPU system. Conclusion: By exploiting GPU acceleration, MC-based, biologically optimized plans were created for small-target tumor patients. This optimizer will be used in an upcoming feasibility trial on LETd painting for radio-resistant tumors.

physics.med-ph↗
arXiv2014

A fast GPU-based Monte Carlo simulation of proton transport with detailed modeling of non-elastic interactions

Purpose: Very fast Monte Carlo (MC) simulations of proton transport have been implemented recently on GPUs. However, these usually use simplified models for non-elastic (NE) proton-nucleus interactions. Our primary goal is to build a GPU-based proton transport MC with detailed modeling of elastic and NE collisions. Methods: Using CUDA, we implemented GPU kernels for these tasks: (1) Simulation of spots from our scanning nozzle configurations, (2) Proton propagation through CT geometry, considering nuclear elastic scattering, multiple scattering, and energy loss straggling, (3) Modeling of the intranuclear cascade stage of NE interactions, (4) Nuclear evaporation simulation, and (5) Statistical error estimates on the dose. To validate our MC, we performed: (1) Secondary particle yield calculations in NE collisions, (2) Dose calculations in homogeneous phantoms, (3) Re-calculations of head and neck plans from a commercial treatment planning system (TPS), and compared with Geant4.9.6p2/TOPAS. Results: Yields, energy and angular distributions of secondaries from NE collisions on various nuclei agree well with the Geant4 Bertini and Binary cascade models. The 3D-gamma pass rate at 2\%-2 mm for treatment plan simulations is typically 98\%. The net calculation time on a NVIDIA GTX680 card, including all data transfers, is $\sim$20 s for $1\times10^7$ proton histories. Conclusions: Our GPU-based MC is the first of its kind to include a detailed nuclear model to handle NE interactions of protons with any nucleus. Dosimetric calculations are in very good agreement with Geant4/TOPAS. Our MC is being used to perform fast routine clinical QA of pencil-beam based treatment plans, and has also been adopted as the dose engine in a clinically-applicable MC-based IMPT TPS. The detailed nuclear modeling will allow us to perform very fast linear energy transfer and neutron dose estimates on the GPU.

physics.med-ph↗
arXiv2014

A graphics processor-based intranuclear cascade and evaporation simulation

Monte Carlo simulations of the transport of protons in human tissue have been deployed on graphics processing units (GPUs) with impressive results. To provide a more complete treatment of non-elastic nuclear interactions in these simulations, we developed a fast intranuclear cascade-evaporation simulation for the GPU. This can be used to model non-elastic proton collisions on any therapeutically relevant nuclei at incident energies between 20 and 250 MeV. Predictions are in good agreement with Geant4.9.6p2. It takes approximately 2 s to calculate $1\times 10^6$ 200 MeV proton-$^{16}$O interactions on a NVIDIA GTX680 GPU. A speed-up factor of $\sim$20 relative to one Intel i7-3820 core processor thread was achieved.

physics.comp-ph↗
arXiv2011

Measurement of the dependence of the light yields of linear alkylbenzene-based and EJ-301 scintillators on electron energy

An experimental test of the electron energy scale linearities of SNO+ and EJ-301 scintillators was carried out using a Compton spectrometer with electrons in the energy range 0.09-3 MeV. The linearity of the apparatus was explicitly demonstrated. It was found that the response of both types of scintillators with respect to electrons becomes non-linear below ~0.4 MeV. An explanation is given in terms of Cherenkov light absorption and re-emission by the scintillators.

nucl-ex↗
arXiv2011

A Monte Carlo simulation of the Sudbury Neutrino Observatory proportional counters

The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an array of 3He proportional counters to the detector. The purpose of this Neutral Current Detection (NCD) array was to observe neutrons resulting from neutral-current solar neutrino-deuteron interactions. We have developed a detailed simulation of the current pulses from the NCD array proportional counters, from the primary neutron capture on 3He through the NCD array signal-processing electronics. This NCD array Monte Carlo simulation was used to model the alpha-decay background in SNO's third-phase 8B solar-neutrino measurement.

physics.ins-det↗
arXiv2007

An array of low-background $^3$He proportional counters for the Sudbury Neutrino Observatory

An array of Neutral-Current Detectors (NCDs) has been built in order to make a unique measurement of the total active flux of solar neutrinos in the Sudbury Neutrino Observatory (SNO). Data in the third phase of the SNO experiment were collected between November 2004 and November 2006, after the NCD array was added to improve the neutral-current sensitivity of the SNO detector. This array consisted of 36 strings of proportional counters filled with a mixture of $^3$He and CF$_4$ gas capable of detecting the neutrons liberated by the neutrino-deuteron neutral current reaction in the D$_2$O, and four strings filled with a mixture of $^4$He and CF$_4$ gas for background measurements. The proportional counter diameter is 5 cm. The total deployed array length was 398 m. The SNO NCD array is the lowest-radioactivity large array of proportional counters ever produced. This article describes the design, construction, deployment, and characterization of the NCD array, discusses the electronics and data acquisition system, and considers event signatures and backgrounds.

nucl-ex↗