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Evaluation of the Effect of Body Habitus and Radiation Therapist On Initial Positioning of Prostate Patients

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R George

R George*, S Stathakis , N Papanikolaou , D Saenz , N Kirby , K Rasmussen , University of Texas HSC SA, San Antonio, TX


SU-I-GPD-J-118 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To determine if there is any correlation between patient weight and deviations between daily alignments performed by different therapists for external beam radiation therapy.

Methods: Cone Beam Computed Tomography (CBCT) images for seven patients throughout the course of their radiation therapy treatment were harvested from Elekta Mosaiq and numerically analyzed. The data included daily shifts and rotations as made by four radiation therapists. Magnitudes of daily shifts based on vertical, longitudinal, and horizontal displacements were analyzed to test if there was a correlation between patient weight and daily alignments. The therapist performing the 3D-3D matching was also considered for our analysis.

Results: Four therapists were included in this study. Average 3D displacements of 0.876 ± 0.232cm, 0.749 ± 0.157cm, 0.702 ± 0.189cm, 0.648 ± 0.217cm were calculated for therapists 1, 2, 3, and 4 respectively. Average 3D displacements of all fractions included in our study was 0.705 cm. Our results show that the patient habitus does have a correlation of R =.68 to the amount of residual shifts. However, a larger sample of patients is required to verify this.

Conclusion: Appropriate training is required for therapists to perform daily 3D-3D image registration using CBCTs and reference CTs. The patient habitus shows a correlation to the daily shift. In the future, a larger number of patients will be evaluated and guidelines will be derived for image registration using CBCTs.

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