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KMID : 1038720130240020085
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Progress in Medical Physics
2013 Volume.24 No. 2 p.85 ~ p.91
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Development of Video Image-Guided Setup (VIGS) System for Tomotherapy: Preliminary Study
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Kim Jin-Sung
Ju Sang-Gyu
Hong Chae-Seon
Jeong Jae-won
Son Ki-hong
Shin Jung-Suk
Shin Eun-Hyuk
Ahn Sung-Hwan
Han Young-Yih
Choi Doo-Ho
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Abstract
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At present, megavoltage computed tomography (MVCT) is the only method used to correct the position of
tomotherapy patients. MVCT produces extra radiation, in addition to the radiation used for treatment, and
repositioning also takes up much of the total treatment time. To address these issues, we suggest the use of
a video image?guided setup (VIGS) system for correcting the position of tomotherapy patients. We developed
an in-house program to correct the exact position of patients using two orthogonal images obtained from two
video cameras installed at 90º and fastened inside the tomotherapy gantry. The system is programmed to make
automatic registration possible with the use of edge detection of the user-defined region of interest (ROI). A
head-and-neck patient is then simulated using a humanoid phantom. After taking the computed tomography
(CT) image, tomotherapy planning is performed. To mimic a clinical treatment course, we used an immobilization
device to position the phantom on the tomotherapy couch and, using MVCT, corrected its position to match
the one captured when the treatment was planned. Video images of the corrected position were used as reference
images for the VIGS system. First, the position was repeatedly corrected 10 times using MVCT, and based on
the saved reference video image, the patient position was then corrected 10 times using the VIGS method.
Thereafter, the results of the two correction methods were compared. The results demonstrated that patient
positioning using a video-imaging method (41.7±11.2 seconds) significantly reduces the overall time of the MVCT
method (420±6 seconds) (p＜0.05). However, there was no meaningful difference in accuracy between the two
methods (x=0.11 mm, y=0.27 mm, z=0.58 mm, p＞0.05). Because VIGS provides a more accurate result and
reduces the required time, compared with the MVCT method, it is expected to manage the overall tomotherapy
treatment process more efficiently.
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KEYWORD
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Tomotherapy, Image guidance, Patient positioning
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