AbstractID: 7694 Title: Image-Guided
Stereotactic Intensity Modulated
Radiosurgery/Radiotherapy
To improve the accuracy of patient positioning in radiotherapy of extracranial tumors, we have developed a novel and innovative
technique based on image-guided stereotactic alignment coupled with intensity modulated radiotherapy. The system consists of a
stereotactic body immobilization system and a LINAC/CT-on-rails unit. This study is only reported on the evaluation of the markedup treatment of spinal tumors. Initially, the patient is immobilized in an individually molded total body vacuum cushion, and is
covered with a thin plastic fixation sheet. Repeated CT scans are taken to assess the spinal column movement due to breathing.
Treatment planning is also performed to obtain an optimal IMRT plan. Prior to the daily treatment, a repeated CT scan is taken. The
planning CT scan is then fused with the daily CT scan, and the isocenter and the treatment plan are updated based on deviation
between the planning CT and the daily CT. The daily updated isocenter is further verified with EPID.
The assessment of spinal column movement due to breathing is less than 0.5 mm. The highly conformal target dose distribution and
sharp dose gradient has allowed us to plan for the tumor dose escalation study and spare the spinal cord. The mean and maximum
isocenter deviation from the treatment plan and the prescribed dose coverage of PTV will be reported. The evaluation of EPID images
will confirm that with this technique is easy to achieve accuracy comparable to that of the invasive head frame for SRS treatment of
intracranial lesions.