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

Abstract

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

Assessing localized dosimetric effects due to unplanned gas cavities during pelvic MR‐guided radiotherapy using Monte Carlo simulations

“…The Graphics Processing Unit Monte Carlo Dose (GPUMCD) calculation algorithm used in the Monaco TPS has been verified to some extent by comparison with independent Monte Carlo algorithms and film measurements. However, given that our results indicate that small volumes on or close to the surface of curved air–tissue boundaries could increase risk of toxicity, the accuracy of the TPS dose calculation for small volumes on density boundaries should be verified …”

“…However, given that our results indicate that small volumes on or close to the surface of curved air-tissue boundaries could increase risk of toxicity, the accuracy of the TPS dose calculation for small volumes on density boundaries should be verified. 45,46 The air-tissue transition gradient in the image used for dose calculation should also be noted when considering the TPS accuracy around air cavities. Uilkema et al found that dose effects of ERE were 20% smaller when calculated using a four voxel air-tissue transition, similar to our study (although different size voxels), compared to an abrupt transition.…”

Machine QA for the Elekta Unity system: A Report from the Elekta MR‐linac consortium

“…Several publications have considered individual aspects of QA on MR-linac devices. Measurement equipment performance, [10][11][12][13][14][15][16][17][18] reference 19 and relative 15,[20][21][22][23] dosimetry within the presence of a magnetic field, treatment planning system, [24][25][26][27][28] Linac, 22,[29][30][31] MR device commissioning, 32,33 and routine QA 32,[34][35][36][37] are the broad range of areas addressed. While not considerably different to conventional RT QA, there are several aspects that need considering.…”

Validation of the RayStation Monte Carlo dose calculation algorithm using a realistic lung phantom

“…We searched articles available to the public from multiple journals concerning lung phantoms. Although a number of phantoms have been tested, including solid water, cork and solid water, balsa wood and solid water, balsa wood and cork, cork and plastic, cork and acrylic, polystyrene and cork, bolus and sponge, foam, and even wood, it appears that we are the first to report open‐access on the use of a cork‐and‐animal‐tissue lung tumor phantom.…”