• Progress in Medical Physics
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• v.26 no.4
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• pp.201-207
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• 2015

The new function of 3DVH software for dose calculation inside the patient undergoing TomoTherapy treatment by applying the measured data obtained by ArcCHECK was recently released. In this study, the dosimetric accuracy of 3DVH for the TomoTherapy DQA process was evaluated by the comparison of measured dose distribution with the dose calculated using 3DVH. The 2D diode detector array MapCHECK phantom was used for the TomoTherapy planning of virtual patient and for the measurement of the compared dose. The average pass rate of gamma evaluation between the measured dose in the MapCHECK phantom and the recalculated dose in 3DVH was $92.6{\pm}3.5%$, and the error was greater than the average pass rate, $99.0{\pm}1.2%$, in the gamma evaluation results with the dose calculated in TomoTherapy planning system. The error was also greater than that in the gamma evaluation results in the RapidArc analysis, which showed the average pass rate of $99.3{\pm}0.9%$. The evaluated accuracy of 3DVH software for TomoTherapy DQA process in this study seemed to have some uncertainty for the clinical use. It is recommended to perform a proper analysis before using the 3DVH software for dose recalculation of the patient in the TomoTherapy DQA process considering the initial application stage in clinical use.

• Progress in Medical Physics
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• v.24 no.2
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• pp.85-91
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• 2013

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 $90^{\circ}$ 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 ($41.7{\pm}11.2$ seconds) significantly reduces the overall time of the MVCT method ($420{\pm}6$ 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.