Iranian Journal of Medical Physics

Iranian Journal of Medical Physics

Evaluation of Six-Dimensional Cranial Target Positioning Accuracy in Two Different Immobilization Methods Using Exactrac System

Document Type : Original Paper

Authors
Tamil Selvan Kasirajan 1
Padma Ganesan 1
Revathy Murugesan Kesavan 1
Arunai Nambi Raj N 2
Senthilnathan K 3
Ramesh Babu P 3
1 Department of Oncology, Apollo Cancer Hospital, Hyderabad, Telangana, India
2 Centre for Biomaterials, Cellular and Molecular Theranostics, Vellore Institute of Technology, Vellore, Tamil Nadu, India
3 Department of Physics, School of Advanced Sciences, Vellore Institute of Technology, Vellore, Tamil Nadu, India
10.22038/ijmp.2019.35652.1448
Abstract
Introduction: The aim of this study was to determine the accuracy of two different immobilization methods in patient positioning in cranial radiotherapy. The six-dimensional (6D) target localization accuracy of using a dedicated stereotactic mask was compared with that of a conventional head mask by the ExacTrac system.
Material and Methods: A total of 56 patients with cranial lesions were included in this study (26 patients with a dedicated stereotactic mask and 30 subjects with a conventional head mask). The ExacTrac image-guided positioning system was utilized to obtain daily translational and rotational patient positioning displacement from the intended position. The 6D setup data was analyzed to obtain population mean, systematic and random errors, and three-dimensional (3D) vector shifts in all the patients.
Results: The population mean values of setup errors were comparable with both immobilization systems; however, the spread as indicated by population systematic and population random errors was more in the use of a conventional head mask. The mean values of the 3D vector shifts were 2.09±1.00 and 4.51±3.38 mm with the use of a dedicated stereotactic mask and conventional head mask, respectively. The frequency distribution of maximum rotational deviation and statistical analysis demonstrated a significant difference in immobilization accuracy between stereotactic immobilization and 3-clamp immobilization (p <0.05).
Conclusion: The results revealed that there was a significant reduction in target positioning errors with a dedicated stereotactic mask, compared to that with a conventional cranial mask. Furthermore, a dedicated stereotactic mask is required to keep rotational deviations within system correctable limits.
Keywords
Radiotherapy
Patient Positioning
Radiosurgery
Radiotherapy Setup Errors
Immobilization
Subjects

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Iranian Journal of Medical Physics
Volume 17, Issue 5
September and October 2020
Pages 308-315

  • Receive Date 18 October 2018
  • Revise Date 10 October 2019
  • Accept Date 11 October 2019