(Saturday, 3/30/2019)
Room: Exhibit Hall
Purpose: The determination of potential collisions between a patient, treatment accessories, and linac mechanical components during treatment planning is important. Studies exploring the use of non-coplanar 4Ï€ radiotherapy involving non-standard treatment couch and gantry orientations have demonstrated significant dosimetric benefits. In this work, a stand-alone collision prediction system (CPS) was developed using MATLAB. This system is based on a straight-forward linac model, developed in this work, that can be used in conjunction with a treatment planning system to predict collisions in 4Ï€ treatments prior to delivery.
Methods: Physical dimensions of the outer mechanical components of a Varian TrueBeam were quantified to construct a geometric model of the linac. A combination of contours from the planning CT and 3-D depth data acquired with a Kinect camera was used to develop a patient specific model. An algorithm that relies on a dot product between vectors denoting linac hardware and patient anatomy is used to predict collisions. Virtual collision test cases were experimentally verified in the treatment room using an ArcCheck phantom to simulate a patient.
Results: For a set of 52 different collision test cases, the positive predictive value and the negative predictive value of the CPS model were calculated to be 0.83 and 1.00, respectively. Validation experiments demonstrate that the CPS consistently estimates collisions at conservative distances from actual collision locations. The average difference between predicted and measured collision states was 2.14 cm for lateral couch movements. The predicted couch rotational position for a collision between the gantry and a patient analog differed from actual values on average by 3.4 degrees.
Conclusion: This study outlines the development and clinical implementation of a solution to 4Ï€ radiotherapy collision management challenges during treatment planning. The CPS will be a valuable tool for treatment planners who seek to implement 4Ï€ radiotherapy.
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