4D modeling in a gimbaled linear accelerator by using gold anchor markers

Publication date: May–June 2018
Source:Reports of Practical Oncology & Radiotherapy, Volume 23, Issue 3
Author(s): Hideharu Miura, Shuichi Ozawa, Takaaki Matsuura, Atsushi Kawakubo, Fumika Hosono, Kiyoshi Yamada, Yasushi Nagata
PurposeThe purpose of this study was to verify whether the dynamic tumor tracking (DTT) feature of a Vero4DRT system performs with 10-mm-long and 0.28mm diameter gold anchor markers.MethodsGold anchor markers with a length of 10mm and a diameter of 0.28mm were used. Gold anchor markers were injected with short and long types into bolus material. These markers were sandwiched by a Tough Water (TW) phantom in the bolus material. For the investigation of 4-dimensional (4D) modeling feasibility under various phantom thicknesses, the TW phantom was added at 2cm intervals (in upper and lower each by 1cm). A programmable respiratory motion table was used to simulate breathing-induced organ motion, with an amplitude of 30mm and a breathing cycle of 3s. X-ray imaging parameters of 80kV and 125kV (320mA and 5ms) were used. The least detection error of the fiducial marker was defined as the 4D-modeling limitation.ResultsThe 4D modeling process was attempted using short and long marker types and its limitation with the short and long types was with phantom thicknesses of 6 and 10cm at 80kV and 125kV, respectively. However, the loss in detectability of the gold anchor because of 4D-modeling errors was found to be approximately 6% (2/31) with a phantom thickness of 2cm under 125kV. 4D-modeling could be performed except under the described conditions.ConclusionsThis work showed that a 10-mm-long gold anchor marker in short and long types can be used with DTT for short water equivalent path length site, such as lung cancer patients, in the Vero4DRT system.



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