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Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
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Surface guided frameless positioning for lung stereotactic body radiation therapy
Sebastian Sarudis1,2, Anna Karlsson1,3, Anna Bäck1,3
1Department of Radiation Physics, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
Journal of Applied Clinical Medical Physics
|August 18, 2021
Summary
Surface guided radiation therapy (SGRT) with frameless immobilization is effective for lung stereotactic body radiation therapy (SBRT). This approach accurately monitors patient and tumor motion, ensuring safe and feasible treatment delivery for lung tumors.
Area of Science:
- Radiation Oncology
- Medical Physics
- Oncology
Background:
- Accurate patient immobilization is critical for effective lung tumor treatment using stereotactic body radiation therapy (SBRT).
- Intra-fractional motion, encompassing both patient and tumor shifts, poses a significant challenge in SBRT delivery.
- Frameless immobilization combined with surface-guided radiation therapy (SGRT) offers a potential solution for motion management.
Purpose of the Study:
- To quantify intra-fractional patient and tumor shifts during lung SBRT using a frameless immobilization and SGRT approach.
- To assess the impact of these shifts on the delivered radiation dose to the gross tumor volume (GTV) and organs at risk (OARs).
- To evaluate the feasibility and effectiveness of SGRT for motion management and respiratory gating in lung SBRT.
Main Methods:
- Collected cone-beam computed tomographies (CBCT) before and after treatment for 137 fractions in 25 lung cancer patients.
- Utilized rigid image registration (6 degrees of freedom) on bony anatomy and visible target volumes to determine patient and tumor shifts.
- Employed a commercial SGRT system for continuous monitoring of patient position and respiration, with automatic beam interruption for shifts >4 mm or deviations outside the gating window.
Main Results:
- Patient shifts were predominantly within 2 mm (vertical/lateral) and 4 mm (longitudinal) in most fractions.
- Tumor shifts were generally within 2-4 mm across all directions, with maximal observed shifts of 4.6 mm (patient) and 7.2 mm (tumor).
- SGRT interrupted treatment in 21% of fractions due to isocenter shifts and 54% due to respiratory excursions, with patients always returning within tolerance. Dose deviations to GTV and OARs remained within acceptable limits.
Conclusions:
- Frameless immobilization combined with SGRT is a feasible and effective strategy for motion management in lung SBRT.
- SGRT provides reliable intra-fractional monitoring and gating, ensuring accurate dose delivery despite patient and tumor motion.
- This approach enhances the safety and precision of SBRT for lung tumors, maintaining target coverage and protecting surrounding healthy tissues.
