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Beyond the Vacuum Bag: A Novel 3D Printed Immobilization Device for VMAT CSI

A Hudson*, N Clements , C Bojechko , C Bagg , D Graham , S Loewen , S Quirk , Tom Baker Cancer Centre, Calgary, AB


(Tuesday, 7/31/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 3

Purpose: A recent transition from 3D-CRT to VMAT treatments for craniospinal irradiation (CSI) necessitated a more rigorous way to immobilize these patients. An immobilization device was created using 3D printed components that allowed for increased accessibility to the spine for setup manipulation; increased patient comfort; and a neutral spine position in the cervical spine area to allow for more homogenous VMAT dose distributions between brain and spine. This immobilization device can be adapted for both pediatric and adult patients with indexing for setup reproducibility.

Methods: A CSI immobilization device was constructed using 3-D printed fully adjustable wedges made of a carbon fiber-like material for lumber spine support and hip support. The device also includes plastic ‘backpack straps’ which ensure shoulders are in a reproducible position for simulation and treatment. The components are indexed to a carbon fiber base which is, in turn, is indexed relative to the thermoplastic mask. 3D printed material has been previously characterized for clinically acceptable surface dose and attenuation for simple treatment geometries. An anthropomorphic phantom was scanned on the new immobilization device and a plan was created to ensure a homogenous dose distribution was achievable and the device did not cause any significant surface dose issues for complex treatment geometries.

Results: Clinically acceptable dose homogeneity was achieved using a VMAT CSI plan in the anthropomorphic phantom and the plan did not show any adverse effects of utilizing the new CSI immobilization device. In addition, surface dose was not increased significantly.

Conclusion: The device presented here allows for increased patient comfort, superior spine neutrality, and accessibility to the patient for fine setup adjustments compared to our previous clinical standard. When included in the CT scan, and therefore the treatment plan, the immobilization device did not lead to any increased inhomogeneity in the treatment.


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