(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: In the SBRT treatment to pancreas, it has been challenging to give sufficient dose to the target while avoiding overdose to adjacent critical structures, especially they are moving with respiratory motion. Two ITV margin reduction techniques to ease this challenge are compared to determine which one is more beneficiary.
Methods: Breath-hold technique: The GTV is contoured on the breath-hold CT (at the end of expiration) which will be fused into the planning CT, i.e. free-breathing CT. The patient will be treated with free-breathing. By comparing fiducial images between the maximum intensity map (derived from 4D CT scan data) and the breath-hold CT, specific ITV margins to each direction of superior, inferior, left, right, anterior and posterior are calculated. Compression technique: An abdominal paddle is imposed to suppress the motion. The GTV is contoured on the free-breathing CT with the compression, and the fiducial motion range on each direction of SI, LR or AP is uniformly added to two ends of the GTV on that direction to make ITV. Data from four pancreas SBRT patients were analyzed.
Results: In average, with the compression technique as compared to the breath-hold technique, the ITV margin is reduced in SI direction by 32.4%, in LR direction by 26.3% and in AP direction by 36.4%.
Conclusion: With the compression technique, ITV can be reduced as compared to the breath-hold technique, which helps dose escalation to the target or dose reduction to critical structures and eventually more effective treatment. More work should be done on the PTV size impact of the compression technique.
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