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Variability of Breast Surface Positioning for Deep Inspiration Breath Hold From An Active Breathing Coordinator

D Stanley

DN Stanley1*, K McConnell1 , K Rasmussen1 , AN Gutierrez1,2 , D Saenz1 , S Stathakis1 , N Papanikolaou1 , N Kirby1 (1) University of Texas Health Science Center San Antonio, San Antonio, Texas 78229 USA. (2)Miami Cancer Institute, Baptist Hospital, Miami, FL 33176 USA.


WE-RAM3-GePD-JT-4 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Joint Imaging-Therapy ePoster Theater

Purpose: The Elekta Active Breathing Coordinator (ABC) utilizes a spirometer based valve system to control breathing and guide deep inspiration breath hold (DIBH). This system has been shown to be accurate in lung cancers but limited analysis has been performed on the spatial accuracy and reproducibility of the breast surface. Recently, the use of optical surface-image guidance for patient positioning has grown in popularity and is an alternative solution for breast DIBH. The aim of this study was to evaluate the variability of the breast positioning for the ABC as measured by the C-RAD 3D surface imaging system.

Methods: Ten volunteers were placed in the treatment position and breathing baselines and inhalation volume threshold baselines were monitored and recorded using the ABC (approved by an Institutional Review Board). Over a period of 60 minutes, the breathing patterns, both normal and DIBH, were recorded by the ABC and CatalystHD. For each breath hold, the valve of the ABC closed at the baseline inhalation threshold and a 3D surface image was acquired. Surface images were exported into MATLAB. For each point on the baseline breast surface, a 3D vector was calculated to the closest point on the subsequent breath hold surface. A root mean square (RMS) vector magnitude was then calculated across the entire surface.

Results: The average and standard deviation across all volunteers for the RMS difference between the baseline and subsequent evaluated images was 7.4 ± 2.8 mm. The average and standard deviation for surface distance in the lateral, longitudinal and vertical directions was 1.6 ± 1.0mm, 2.5 ± 3.8mm and 8.7 ± 6.7mm, respectively.

Conclusion: This study shows that even though inhalation volume is kept constant a non-negligible variability of the breast surface position exists.

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