Commissioning and quality assurance of Dynamic WaveArc irradiation.

Sayaka Sato,Yuki Miyabe,Kenji Yokota,Mitsuhiro Nakamura,Shuji Kaneko,Masahiro Yamada,Kunio Takahashi,Hajime Monzen,Masahiro Hiraoka,Takashi Mizowaki,Yoshitomo Ishihara

doi:10.1120/jacmp.v16i2.5080

Sayaka Sato, Yuki Miyabe + Show 9 more

Open Access

https://doi.org/10.1120/jacmp.v16i2.5080

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Abstract

A novel three‐dimensional unicursal irradiation technique “Dynamic WaveArc” (DWA), which employs simultaneous and continuous gantry and O‐ring rotation during dose delivery, has been implemented in Vero4DRT. The purposes of this study were to develop a commissioning and quality assurance procedure for DWA irradiation, and to assess the accuracy of the mechanical motion and dosimetric control of Vero4DRT. To determine the mechanical accuracy and the dose accuracy with DWA irradiation, 21 verification test patterns with various gantry and ring rotational directions and speeds were generated. These patterns were irradiated while recording the irradiation log data. The differences in gantry position, ring position, and accumulated MU (EG,ER, and EMU, respectively) between the planned and actual values in the log at each time point were evaluated. Furthermore, the doses delivered were measured using an ionization chamber and spherical phantom. The constancy of radiation output during DWA irradiation was examined by comparison with static beam irradiation. The mean absolute error (MAE) of EG and ER were within 0.1° and the maximum error was within 0.2°. The MAE of EMU was within 0.7 MU, and maximum error was 2.7 MU. Errors of accumulated MU were observed only around control points, changing gantry, and ring velocity. The gantry rotational range, in which EMU was greater than or equal to 2.0 MU, was not greater than 3.2%. It was confirmed that the extent of the large differences in accumulated MU was negligibly small during the entire irradiation range. The variation of relative output value for DWA irradiation was within 0.2%, and this was equivalent to conventional arc irradiation with a rotating gantry. In conclusion, a verification procedure for DWA irradiation was designed and implemented. The results demonstrated that Vero4DRT has adequate mechanical accuracy and beam output constancy during gantry and ring rotation.PACS number: 87

Highlights

The Vero4DRT (MHI-TM2000, Mitsubishi Heavy Industries, Ltd., Hiroshima, Japan, and BrainLAB, Feldkirchen, Germany) is a unique image-guided radiotherapy system,(1-3) consisting of an O-ring gantry that is designed to rotate ± 185° around a patient a Corresponding author: Yuki Miyabe, Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawaharacho, Sakyo-ku, Kyoto, Japan; phone: 74 Sato et al.: Commissioning and quality assurance (QA) of Dynamic WaveArc and ± 60° around its vertical axis
Using the mechanical features of the O-ring gantry, a novel three-dimensional unicursal irradiation method, called “Dynamic WaveArc” (DWA), which uses simultaneous and continuous gantry and ring rotation during dose delivery, has been developed.[4]. DWA is an advanced conformal arc irradiation technique allowing more flexibility in irradiation direction, and it enables efficient dose delivery avoiding the organ at risk (OAR)
We developed a commissioning and quality assurance (QA) procedure for DWA irradiation, and verified the accuracy of the mechanical motion and dosimetric control of Vero4DRT

Summary

Introduction

In Vero4DRT, the O-ring gantry rotates around the vertical axis instead of rotating around the treatment couch. Noncoplanar irradiation can be performed without moving a patient by ring rotation. Irradiation during continuous ring rotation can be performed mechanistically. Using the mechanical features of the O-ring gantry, a novel three-dimensional unicursal irradiation method, called “Dynamic WaveArc” (DWA), which uses simultaneous and continuous gantry and ring rotation during dose delivery, has been developed.[4] DWA is an advanced conformal arc irradiation technique allowing more flexibility in irradiation direction, and it enables efficient dose delivery avoiding the organ at risk (OAR). In the initial investigation with a planning study,(4) a comparison of the treatment plan in pancreatic cancer by DWA, a conventional dynamic conformal arc irradiation, and intensity-modulated radiation therapy (IMRT) was performed. It was found that the dose-volume data of DWA were comparable to those of IMRT in relation to both the target and the OARs, and the monitor unit (MU) was

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