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What Is the Optimal Inflation Level of Tissue Expanders to Minimize Dose Perturbations Caused by Magnetic Port?

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H amro

H amro*, E Perevalova , B McCabe , C Stepaniak , D Golden , M Endara , B Aydogan , A McCall , The University of Chicago, Chicago, IL


SU-I-GPD-T-499 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Breast tissue expanders are commonly used in women post-mastectomy for chest wall reconstruction. Magnetic ports are known to cause radiation dose perturbations. The effect of expander size and expansion volume on dose perturbations has not been previously reported. This study evaluates radiation dose perturbations due to the tissue expander magnetic port and evaluates the optimal inflation of the expanders to minimize dose perturbations.

Methods: Four breast phantoms were constructed using 500 and 720 cc expanders. Phantoms were constructed for each expander size while fully inflated and deflated (inflated to 140 cc). Radiation treatment plans were developed using the Pinnacle3 treatment planning system and used to treat the phantoms. Two dimensional dose distributions were measured using EBT3 films on the chest wall underneath the expanders and on the lateral, medial, superior, inferior, and anterior surfaces of the expanders.

Results: 2D dose distributions measured at the various regions of the expander were compared for all four phantoms. For each of the expanders used in this study, the measured dose to the chest wall underneath the expander showed a hot area (~110% of prescribed dose) when the expanders were fully deflated and a more uniform dose distribution without the hot region when the expanders were fully inflated. No clinically significant differences in dose distributions were measured between the two different expander volumes. Dose distributions measured at the superior and inferior surfaces of fully inflated expanders showed hot areas measuring ~110% of the prescribed dose. Lateral and medial dose distributions measured for fully expanded expanders showed the expected cold spots reported in the literature.

Conclusion: Expander inflation level has an impact on the dose perturbation caused by the magnetic port of tissue breast expander. Further measurements using a broader range of expander sizes with incremental expansion volumes are underway at our institution.

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