Prog Med Phys.  2016 Sep;27(3):169-174. 10.14316/pmp.2016.27.3.169.

Treatment Plan Delivery Accuracy of the ViewRay System in Two-Headed Mode

• Park JM
• Park SY
• Wu HG
• Kim JI

• KMID: 2376548
• DOI: http://doi.org/10.14316/pmp.2016.27.3.169

Abstract

The aim of this study is to investigate the delivery accuracy of intensity-modulated radiation therapy (IMRT) plans in the two-headed mode of the ViewRayâ„¢ system in comparison with that of the normal operation treatment plan of the machine. For this study, a total of eight IMRT plans and corresponding verification plans were generated (four head and neck, two liver, and two prostate IMRT plans). The delivered dose distributions were measured using ArcCHECKâ„¢ with the insertion of an ionization chamber. We measured the delivered dose distributions in three-headed mode (normal operation of the machine), two-headed mode with head 1 disabled, two-headed mode with head 2 disabled, and two-headed mode with head 3 disabled. Therefore, a total of four measurements were performed for each IMRT plan. The global gamma passing rates (3%/3 mm) in three-headed mode, head 1 disabled, head 2 disabled, and head 3 disabled were 99.9±0.1%, 99.8±0.3%, 99.6±0.7%, and 99.7±0.4%, respectively. The difference in the gamma passing rates of the three- and two-headed modes was insignificant. With 2%/2 mm, the rates were 96.6±3.6%, 97.2±3.5%, 95.7±6.2%, and 95.5±4.3%, respectively. Between three-headed mode and head 3 disabled, a statistically significant difference was observed with a p-value of 0.02; however, the difference was minimal (1.1%). The chamber readings showed differences of approximately 1% between three- and two-headed modes, which were minimal. Therefore, the treatment plan delivery in the two-headed mode of the ViewRayâ„¢ system seems accurate and robust.

Keyword

MRI-guided radiation therapy system; Two-headed mode; Co-60; Intensity modulated radiation therapy

MeSH Terms

Head
Liver
Neck
Prostate
Reading

Figure

• 

  Fig. 1 Measured dose distributions with the ArcCHECKTM of the intensity modulated radiation therapy (IMRT) plan for the treatment of head and neck cancer. The failed points by the gamma-index method with a 2%/2 mm gamma criterion are shown in red (measured value＞calculated value) and blue (measured value＜calculated value) colors. The distributions of the three-headed mode (a), two-headed mode with head 1 disabled (b), two-headed mode with head 2 disabled (c) and two-headed mode with head 3 disabled (d) are shown.

• 

  Fig. 2 Measured dose distributions with the ArcCHECKTM of the intensity modulated radiation therapy (IMRT) plan for the treatment of head and neck cancer. The failed points by the gamma-index method with a 3%/3 mm gamma criterion are shown in red (measured value＞calculated value) and blue (measured value＜calculated value) colors. The distributions of the three-headed mode (a), two-headed mode with head 1 disabled (b), two-headed mode with head 2 disabled (c) and two-headed mode with head 3 disabled (d) are shown.

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