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check (MPC) method, which is one of the major modes of TrueBeam. In MPC, the MLC position is detected with a comb-like MLC pattern and the jaw position is detected in an 18 × 18 cm2 open field. A study that compared MPC with external QA procedures reported that X jaw offsets were detected within 0.10 mm23). However, the MPC method evaluates only a single static jaw position, whereas our method can evaluate jaw positions in eight different segments and multiple MLC posi-tions, equivalent to the capabilities of the conven-tional PF pattern.The limitation of our method is that Y jaw posi-tions with JTT cannot be evaluated in the present BPF pattern. Although static Y jaw positions can be evaluated with the same method as X jaws, a PF-like image cannot be created when JTT is applied to Y jaws. We are currently developing a pattern that can create a PF-like image even if JTT is applied to the Y jaws, and we will report our study results in a future publication.In conclusion, we developed the BPF plan to verify jaw positions during jaw-tracking delivery. Using the BPF plan, the positions of jaws were verified with accuracy of 0.16 ± 0.19 mm for the X1 jaw and 0.11 ± 0.16 mm for the X2 jaw. Further-more, we verified that a PF-like image can be created by accumulating the cine images and used as a conventional PF test for MLC.AcknowledgmentsNot applicable.Figure 5　Cine image frames in segment 4 and 5: a) cine image frame of segment 4; b) cine image frame of segment 5. 1) Otto K: Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys, 2008; 35: 310-317. 2) Schmidhalter D, Fix MK, Niederer P, Mini R, Manser P: Leaf transmission reduction using moving jaws for dynamic MLC IMRT. Med Phys, 2007; 34: 3674-3687. 3) Feng Z, Wu H, Zhang Y, Zhang Y, Cheng J, Su X: Dosimetric comparison between jaw tracking and static jaw techniques in intensity-modulated radio-therapy. Radiat Oncol, 2015; 10: 28. 4) Snyder KC, Wen N, Huang Y, et al: Use of jaw tracking in intensity modulated and volumetric modulated arc radiation therapy for spine stereotactic radiosurgery. Pract Radiat Oncol, 2015; 5: e155-e162. 5) Park B, Cho B, Kim J, Lee S, Ahn S: Kwak J: Dosim-etric impact of the jaw-tracking technique in volu-metric modulated arc therapy. J Nucl Med Radiat Ther, 2016; 7: 1-9. 6) Chow JCL, Seguin M, Alexander A: Dosimetric effect No funding was received.TK, SS, CK, KU, TI, HN, HW, and KS partici-pated in the study design and data interpretation. KT and SS performed the measurements. KT mainly analyzed and interpreted the measured data. KT and SS were major contributors in writing the manuscript. All authors read and approved the final manuscript.The authors declare that there are no conflicts of interest.597FundingAuthor contributionsConflicts of interest statementReferences