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Low-Cost Immobilization Techniques for Whole-Brain Irradiation

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S Gay

S Gay*, A Rubinstein , W Ingram , B Anderson , X Fave , R Ger , R McCarroll , C Owens , T Netherton , K Kisling , L Court , J Yang , Y Li , J Lee , D Mackin , C Cardenas , The University of Texas MD Anderson Cancer Center, Houston, TX


TU-C3-GePD-TT-5 (Tuesday, August 1, 2017) 10:30 AM - 11:00 AM Room: Therapy ePoster Theater

Purpose: To investigate the inter- and intra-fraction movement associated with the use of two simple tape-based immobilization techniques for whole-brain irradiation as an alternative to conventional thermoplastic immobilization masks. The results of this study are of interest to clinical staff with limited resources (e.g. low- or middle-income countries), as well as for patients who cannot tolerate conventional immobilization masks, such as those suffering from severe claustrophobia.

Methods: Setup reproducibility of eight healthy volunteers was assessed for two different immobilization techniques: (1) One strip of tape was positioned across the volunteer’s forehead and secured to the sides of the treatment couch, (2) A second strip was added under the volunteer’s chin and secured to the superior aspect of the treatment couch. Volunteers were positioned five times per technique to allow calculation of inter-fraction reproducibility measurements, with a short break between sessions. After each positioning, anterior and lateral photographs were acquired. To estimate intra-fraction movement, five-minute anterior and lateral videos were taken for both techniques per volunteer. In-house software was used to analyze the photographs and videos, and to determine both setup reproducibility and inter- and intra-fraction movement. This method was validated using a video with a marker shifted 10mm in both longitudinal and lateral directions. Since the marker corners must be manually selected for pixel-size calibration, the video was measured ten times to test the manual selection consistency.

Results: Intra-fraction movement directly increased with time on couch, giving a maximum intra-fraction displacement for all volunteers of 2.8mm. The maximum inter-fraction range of motion was 5.4mm. For both techniques, the magnitude of inter- and intra-fraction movement was comparable to that reported for conventional thermoplastic masks when used for whole-brain irradiation.

Conclusion: These results indicate that simple tape-based immobilization techniques could provide a viable, economical alternative to the thermoplastic mask.

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