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A Feasibility Study of Computer Milled Immobilization Cradles for Head and Neck Radiotherapy

J Deasy

P Booth , N Lee , D Lovelock , K Hwang , M Hunt , E Yorke , J Deasy*, Memorial Sloan Kettering Cancer Center, New York, NY


SU-I-GPD-T-75 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Facemasks used to immobilize head and neck (H&N) radiotherapy patients are very uncomfortable, and often not well tolerated by all patients. A process has been developed for head and neck immobilization that involves the custom milling of a radiolucent foam to create a comfortable mold. We hypothesize H&N patients can be comfortably immobilized for their treatment without the need for a facemask.

Methods: The proposed treatment process is to acquire the planning MR or CT scan with the patient lying on a cushioned couch top and a standard head rest. In order to maximize comfort, no face mask is used. The outer contour extracted from the scan would be used to generate a custom mold that would be used for subsequent immobilization during treatment. To demonstrate feasibility, 3D models of the skin surface of five volunteers accrued to an IRB approved protocol were constructed from the MR scans. The models are processed in CAD to create a negative mold of the posterior patient surface extending anteriorly to the coronal midline using expanded foam. Volunteers will be placed in their molds approximately four times at bi-weekly intervals and re-scanned using MRI. Bony registration from the initial to each subsequent scan will be used to assess the immobilization performance.

Results: Initial prototypes showed promise in comfort and fit. Modest immobilization, such as a chinstrap, could be used during the planning scan. Patient hair must be arranged carefully, generally pulled first to the side and then forwards.

Conclusion: A process to mill custom immobilization molds from expanded foam using the planning scan has been developed. This process will facilitate a new simulation and immobilization workflow for H&N patients without the use of a facemask. Patients will be treated using this technique and results will be reported.

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