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Skin Dose Comparison of CyberKnife and Helical Tomotherapy for Head-and-Neck Stereotactic Body Radiotherapy
Prog. Med. Phys. 2019;30(1):1-6
Published online March 31, 2019
© 2019 Korean Society of Medical Physics.

Jeongmin Yoon1, Kwangwoo Park2, Jin Sung Kim2, Yong Bae Kim2, Ho Lee3

1Department of Radiation Oncology, Seoul National University Hospital, 2Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, 3Department of Radiation Oncology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
Correspondence to: Ho Lee, (
Tel: 82-2-2228-4363, Fax: 82-2-2227-7823
Received December 3, 2018; Revised December 30, 2018; Accepted January 7, 2019.
This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Purpose: This study conducts a comparative evaluation of the skin dose in CyberKnife (CK) and Helical Tomotherapy (HT) to predict the accurate dose of radiation and minimize skin burns in head-and-neck stereotactic body radiotherapy.

Materials and Methods:
Arbitrarily-defined planning target volume (PTV) close to the skin was drawn on the planning computed tomography acquired from a head-and-neck phantom with 19 optically stimulated luminescent dosimeters (OSLDs) attached to the surface (3 OSLDs were positioned at the skin close to PTV and 16 OSLDs were near sideburns and forehead, away from PTV). The calculation doses were obtained from the MultiPlan 5.1.2 treatment planning system using raytracing (RT), finite size pencil beam (FSPB), and Monte Carlo (MC) algorithms for CK. For HT, t he s kin d ose w as e stimated v ia c onvolution s uperposition ( CS) a lgorithm f rom t he Tomotherapy planning station The prescribed dose was 8 Gy for 95% coverage of the PTV.

Results and Conclusions:
The mean differences between calculation and measurement values were −1.2±3.1%, 2.5±7.9%, −2.8±3.8%, −6.6±8.8%, and −1.4±1.8% in CS, RT, RT with contourcorrection (CC), FSPB, and MC, respectively. FSPB showed a dose error comparable to RT. CS and RT with CC led to a small error as compared to FSPB and RT. Considering OSLDs close to PTV, MC minimized the uncertainty of skin dose as compared to other algorithms.
Keywords : CyberKnife, Skin dose, Helical TomoTherapy, SBRT

March 2019, 30 (1)