GPU-based cross-platform Monte Carlo proton dose calculation engine in the framework of Taichi

In recent years,graphics processing units(GPUs)have been applied to accelerate Monte Carlo(MC)simulations for proton dose calculation in radiotherapy.Nonetheless,current GPU platforms,such as Compute Unified Device Architecture(CUDA)and Open Computing Language(OpenCL),suffer from cross-platform limitation or relatively high programming barrier.However,the Taichi toolkit,which was developed to overcome these difficulties,has been successfully applied to high-performance numerical computations.Based on the class II condensed history simulation scheme with various proton-nucleus interactions,we developed a GPU-accelerated MC engine for proton transport using the Taichi toolkit.Dose distributions in homogeneous and heterogeneous geometries were calculated for 110,160,and 200 MeV protons and were compared with those obtained by full MC simulations using TOPAS.The gamma passing rates were greater than 0.99 and 0.95 with criteria of 2 mm,2%and 1 mm,1%,respectively,in all the benchmark tests.Moreover,the calculation speed was at least 5800 times faster than that of TOPAS,and the number of lines of code was approximately 10 times less than those of CUDA or OpenCL.Our study provides a highly accurate,efficient,and easy-to-use proton dose calculation engine for fast prototyping,beamlet calculation,and education purposes.

Effects of CT based Voxel Phantoms on Dose Distribution Calculated with Monte Carlo Method

A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient’s anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.

Impact of dose calculation algorithm on radiation therapy

The quality of radiation therapy depends on the ability to maximize the tumor control probability while minimizing the normal tissue complication probability.Both of these two quantities are directly related to the accuracy of dose distributions calculated by treatment planning systems.The commonly used dose calculation algorithms in the treatment planning systems are reviewed in this work.The accuracy comparisons among these algorithms are illustrated by summarizing the highly cited research papers on this topic.Further,the correlation between the algorithms and tumor control probability/normal tissue complication probability values are manifested by several recent studies from different groups.All the cases demonstrate that dose calculation algorithms play a vital role in radiation therapy.

Acuros-Based Planning with Density Override for Lung SBRT by a Dynamic Conformal Arc Technique: Comparative Evaluation with AAA-Based Planning in Four-Dimensional Dose

The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison with AAA without and with the override. Ten lung-tumor patients were selected with each PTV size around 2 - 4 cm and were imaged using slow scan, followed by four-dimensional (4D) imaging limited to the target. On each phase-specific image, gross tumor volume (GTV) was contoured. Summed over all phases, an integrated GTV (iGTV) was generated and copied to the slow scan. A treatment plan was created using a dynamic-conformal-arc technique with AAA to prescribe 60 Gy to 95% of PTV (iGTV + 0.5 cm). Each AAA-based plan was regenerated by overriding the density of the setup margin of PTV by GTV density (modeling tumor-position uncertainty). It was also regenerated with Acuros and the override. The three plans were validated in 4D dose to PTV, after similarly overriding PTV density (phase-specific), accurately calculating with Acuros, and summing the phase-specific plans through organ/dose registration. The Acuros-based plan with the override, the AAA-based plan, and the AAA-based plan with the override provided 4D PTV doses of 63.9, 67.9, and 62 Gy at D95%, respectively, averaged over all patients. The override with Acuros and AAA produced lesser 4D doses, closer to the associated 3D doses, respectively, than that without the override, with better conformity and inhomogeneity. With the override in common, Acuros provided a greater dose to PTV than that by AAA. The Acuros with the override, which was more accurate than the AAA without the override, is clinically recommended.

The impact of intensity modulated radiotherapy on the skin dose for deep seated tumors

Objective: The purpose of this study was to investigate the impact of intensity modulated radiotherapy (IMRT) on surface doses for brain, abdomen and pelvis deep located tumors treated with 6 MV photon and to evaluate the skin dose calculation accuracy of the XIO 4.04 treatment planning system. Methods: More investigations for the influences of IMRT on skin doses would increase its applications for many treatment sites. Measuring skin doses in real treatment situations would reduce the uncertainty of skin dose prediction. In this work a pediatric human phantom was covered by a layer of 1 mm bolus at three treatment sites and thermoluminescent dosimeter (TLD) chips were inserted into the bolus at each treatment site before CT scan. Two different treatment plans [three-dimensional conformal radiation therapy (3DCRT) and IMRT] for each treatment sites were performed on XIO 4.04 treatment planning system using superposition algorism. Results: The results showed that the surface doses for 3DCRT were higher than the surface doses in IMRT by 1.6%, 2.5% and 3.2% for brain, abdomen and pelvis sites respectively. There was good agreement between measured and calculated surface doses, where the calculated surface dose was 15.5% for brain tumor calculated with 3DCRT whereas the measured surface dose was 12.1%. For abdomen site the calculated surface dose for IMRT treatment plan was 16.5% whereas the measured surface dose was 12.6%. Conclusion: The skin dose in IMRT for deep seated tumors is lower than that in 3DCRT which is another advantage for the IMRT. The TLD readings showed that the difference between the calculated and measured point dose is negligible. The superposition calculation algorism of the XIO 4.04 treatment planning system modeled the superficial dose well.

An Assessment of Ingestion Dose due to the Intake of ^210Po and ^210Pb through Drinking Water of Eloor, Ernakulam District, Kerala, India

The present study aims at measuring the activity concentrations of ^210Po and ^210Pb in the potable water of Eloor, a major industrial belt in the Ernakulam district of Kerala, India with an aim of evaluating resultant ingestion dose to critical population. The industrial units located in Eloor discharge their treated effluents into the river Periyar and the surrounding environs. The two major industries of interest with respect to NORMs are the fertilizer plant, processing rock phosphate and the monazite processing plant, which had been in operation for the last 50 years. For sampling, Eloor region was divided into four zones and a total of 55 water samples from different locations were collected and analysed as per standard analytical procedure manual of BARC. The ^210Po concentration ranged between 0.3 to 4.7 mBq.L^-1 and ^210Pb ranged from 0.6 to 4.3 mBq.L^-1. All values are well below the limit of 0.1 Bq.Ll recommended by World Health Organization. Statistical analysis shows a good co-relation between ^210Po and ^210Pb in the water samples analyzed and the mean activity concentration is found to be relatively high in the western region of Eloor compared to other regions. The annual effective dose equivalent to man from ^210Po and ^210Pb through drinking water intake were estimated and found to be 1.13 μSv.y^-1 and 0.99 μSv.y^-1 respectively, which is well below the reference level of committed effective dose （100 μSv.y^-1） recommended by WHO.

BECK FOUMULA REVISION FOR ^(222)Rn ESCAPE AND WATER CONTENT IN SOIL

This paper points out the limitation of Beck formula and gives a revised formula owing to the water content and 222Rn escape in soil for calculating γ radiation doserate through the experimental fitting from 576 sets of measured values in ZhejiangProvince. When the revised formula is applied to Beijing Municipality, where there is a great difference in the meteorology and soil conditions, the calculated average in general is only 3.5% different from that measured; those of every position deviate only 2.1% averagely; and their dispersion is in the experimental errors. Therefore, the revised formula possesses a high reliability and a broad suitability, and is an effective method to estimate the ac radiation dose rate oil the land.

Monte Carlo simulations for targeted beta therapy: An optimization for liver lesions and comparison of dose distributions in other organs

Objective:To optimize targeted beta therapy for liver lesions in adult male phantom by comparing the efficacy and safety profiles of five different beta-emitting radionuclides:90Y,166Ho,153Sm,47Sc,and 177Lu.Methods:This study includes Monte Carlo simulations of the behavioral characteristics of five different beta emitters that have current or potential use in targeted beta therapy.The energy loss of beta particles moving within the material through ionization or chemical processes,the energy transferred to the material,the energy lost by beta particles along the distance traveled within the tissue,and consequently,the stopping power are calculated using the Bethe-Bloch formula.The CSDA(continuous slowing-down approximation)range of beta particles within the tissue is examined using ESTAR and GEANT codes,while the stopping power of the tissue is investigated using FLUKA,ESTAR,and GEANT codes.Tissue dose calculations for the target organ are obtained using the IDAC-Dose2.1 and MIRDcalc simulation programs,using parameters such as absorbed dose per accumulated activity(S-factor)and specific absorbed fraction(SAF).Additionally,dose and flux values are obtained using the PHITS program.Results:The behaviors and dose contribution of beta particles in liver tissue have been addressed in various ways.90Y,which has the highest average beta energy,was observed to provide a higher absorbed dose value in the liver compared to other beta-emitting isotopes,while the lowest absorbed dose was observed with 177Lu.In other organs,it has been observed that 90Y and 47Sc contribute to a higher absorbed dose compared to other betaemitting isotopes.Conclusions:This study emphasizes the complexity and significance of targeted beta therapy optimization.

Photon Dose Calculation Method Based on Monte Carlo Finite-Size Pencil Beam Model in Accurate Radiotherapy

This study mainly focused on the key technologies,the photon dose calculation based on the Monte Carlo Finite-Size Pencil Beam(MCFSPB)model in the Accurate Radiotherapy System(ARTS).In the MCFSPB model,the acquisition of pencil beam kernel is one of the most important technologies.In this study,by analyzing the demerits of the clinical pencil beam dose calculation methods,a new pencil beam kernel model was developed based on the Monte Carlo(MC)simulation and the technology of medical accelerator energy spectrum reconstruction.which greatly improved the accuracy of calculated result.According to the axial symmetry principle,only part of simulation results was used for the data of pencil beam kernel,which greatly reduced the data quantity of the pencil beam and reduced calculated time.Based on the above studies,the MCFSPB method was designed and implemented by the Visual C++development tool.With several tests including the comparisons among the American Association of Physicists in Medicine(AAPM)No.55 Report sample and the ion chamber measurement of lung-simulating inhomogeneous phantom in clinical treatment plan,the results showed that the maximum error of most calculated point was less than 0.5%in the homogeneous phantom and less than 3%in the heterogeneous phantom.This method met the clinical criteria,and would be expected to be used as a fast and accurate dose engine for clinic TPS.