Program Information
Simultaneous Analysis of 2D-KV, Cone Beam CT, and MV Image Centers for Image-Guided Radiation Therapy Phantom Using Single Setup with Free Software
S Nishiyama1*, K Makabe2 , M Kuramochi1 , T Suzuki1 , H Tomita1 , (1) Saiseikai Kawaguchi General Hospital, Kawaguchi, Saitama, (2) Kuki General Hospital, Kuki, Saitama,
Presentations
SU-J-CAMPUS-JT-3 (Sunday, July 30, 2017) 4:00 PM - 5:00 PM Room: Joint Imaging-Therapy Theater
Purpose: We have developed a method for simultaneous analysis of the central axis of two-dimensional (2D) kV images, cone beam computed tomography (CBCT) images and MV images for image-guided radiation therapy (IGRT) phantoms in a single setup, and report the accuracy of our method and the measurement experience when using an Elekta Synergy linac.
Methods: (1) 2D kV and MV images of the IGRT phantom were scanned from four different directions (0°, 90°, 180°, 270°). The data from both sets of images were imported into free image analysis software, and the central coordinates were then input into Microsoft Excel software and graphed. (2) The known measurement accuracy with respect to shifts in the various treatment energy levels was verified. (3) Quality assurance (QA) of the central axes of the 2D kV, CBCT and MV images obtained in our hospital was performed by varying the treatment energies.
Results: (1) The errors between the centers of the 2D kV, CBCT and MV images could be evaluated visually. (2) The total shift errors when compared with that at the 4 MV level, expressed as the mean ± standard deviation (maximum), were −0.001 ± 0.111 (0.116) mm at 6 MV and 0.053 ± 0.077 (0.152) mm at 10 MV. (3) At 6 MV and at 10 MV, the errors were within tolerable limits, but the error at 4 MV exceeded 1 mm.
Conclusion: Our method enabled simultaneous high-accuracy analysis of the central axes of 2D kV, CBCT and MV images, and demonstrated that the center of the irradiation field changed as a result of differences in the treatment energy used. The central axis of the MV images may also vary depending on the type of treatment energy used. Our developed QA method can show these energy-dependent differences in detail.
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