Intrafractional Baseline Shift or Drift of Lung Tumor Motion During Gated Radiation Therapy With a Real-Time Tumor-Tracking System

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• 作者：Seishin Takao ; PhD^&lowast ; ; Naoki Miyamoto ; PhD^&lowast ; ; Taeko Matsuura ; PhD^&lowast ; ; Rikiya Onimaru ; MD^&dagger ; ; Norio Katoh ; MD^&Dagger ; ; Tetsuya Inoue ; MD^&Dagger ; ; Kenneth Lee Sutherland ; PhD^&lowast ; ; Ryusuke Suzuki ; PhD^&lowast ; ; Hiroki Shirato ; MD^&dagger ; ; ^§ ; ; Shinichi Shimizu ; MD^§ ; ; ^‖ ; ^{sshing@med.hokudai.ac.jp" class="auth_mail" title="E-mail the corresponding author}
• 刊名：International Journal of Radiation Oncology*Biology*Physics
• 出版年：2016
• 出版时间：1 January 2016
• 年：2016
• 卷：94
• 期：1
• 页码：172-180
• 全文大小：1809 K

文摘

To investigate the frequency and amplitude of baseline shift or drift (shift/drift) of lung tumors in stereotactic body radiation therapy (SBRT), using a real-time tumor-tracking radiation therapy (RTRT) system.

Methods and Materials

Sixty-eight patients with peripheral lung tumors were treated with SBRT using the RTRT system. One of the fiducial markers implanted near the tumor was used for the real-time monitoring of the intrafractional tumor motion every 0.033 seconds by the RTRT system. When baseline shift/drift is determined by the system, the position of the treatment couch is adjusted to compensate for the shift/drift. Therefore, the changes in the couch position correspond to the baseline shift/drift in the tumor motion. The frequency and amount of adjustment to the couch positions in the left-right (LR), cranio-caudal (CC), and antero-posterior (AP) directions have been analyzed for 335 fractions administered to 68 patients.

Results

The average change in position of the treatment couch during the treatment time was 0.45 ± 2.23 mm (mean ± standard deviation), −1.65 ± 5.95 mm, and 1.50 ± 2.54 mm in the LR, CC, and AP directions, respectively. Overall the baseline shift/drift occurs toward the cranial and posterior directions. The incidence of baseline shift/drift exceeding 3 mm was 6.0%, 15.5%, 14.0%, and 42.1% for the LR, CC, AP, and for the square-root of sum of 3 directions, respectively, within 10 minutes of the start of treatment, and 23.0%, 37.6%, 32.5%, and 71.6% within 30 minutes.

Conclusions

Real-time monitoring and frequent adjustments of the couch position and/or adding appropriate margins are suggested to be essential to compensate for possible underdosages due to baseline shift/drift in SBRT for lung cancers.