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Patient-Specific Quality Assurance of Respiratory-Gated Radiotherapy for Lung Using New Real-Time Tumor-Tracking Radiotherapy System

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T Shiinoki

T Shiinoki1*, T Uehara2 , T Sera2 , Y Yuasa1,2 , K Fujimoto1,2 , M Koike2 , H Hanazawa1 , K Shibuya1 , (1) Yamaguchi University, Ube, ,(2) Yamaguchi University Hospital, Ube, Yamaguchi,


SU-I-GPD-J-45 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The respiratory gating system combined the TrueBeam and a new real-time tumor-tracking radiotherapy system, SyncTraX (Shimadzu Co., Japan) was installed. The SyncTraX consists of two x-ray tubes and color image intensifiers. Using fluoroscopic images, the fiducial marker which was implanted near the tumor was tracked and was used as the internal surrogate for respiratory gating. The purpose of this study was to perform the patient-specific quality assurance (QA) for respiratory-gated SBRT using SyncTraX.

Methods: Seven patients who underwent respiratory-gated SBRT of lung using SyncTraX were enrolled in this study. Log files which recoded the 3D coordinate of the fiducial marker implanted near the tumor were acquired for all patients using SyncTraX before treatment. Log files were convert to the input file to drive the programmable respiratory motion phantom. The phantom was driven in superior-inferior direction. For moving phantom, respiratory-gated SBRT using SyncTraX was performed, then absolute dose and dose distribution were measured using a micro chamber and Gafchromic films. The differences between measured and calculated absolute dose were calculated. The dose distributions were compared with those calculated using gamma analysis (criteria: 3%/3 mm, threshold: 30%). The relationship between error of absolute and relative dose and respiratory motion was analyzed.

Results: The differences between measured and calculated absolute dose were 0.3±1.0% (range:-1.3−1.4%). The gamma pass rate of γ3%/3 mm were 98.3±1.3% (range:96.6−99.5%). There were no correlations between the error of absolute, relation dose and respiratory motion.

Conclusion: We have demonstrated that patient-specific QA for respiratory-gated radiotherapy using SyncTraX. Our results showed respiratory-gated radiotherapy using SyncTraX was clinically performed with high accuracy.

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