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A Study On the Margin for Monitoring Inhaling-Breath-Hold When Treating the Left-Sided Breast

L Xiong*, R Schoenthaler , J McGrath , Massachusetts General Hospital, Concord, MA


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Patients using deep-inhaling-breath-hold will have the advantage of larger space between the heart and breast, therefore, less dose exposure to the heart when treated to the left sided breasts. It is a challenge to know during treatment if the patients reproduced the planning position and what error margin is adequate during the monitoring. This work studies the breast and heart motion, based on geometry of patients with and without inhaling-breath-hold.

Methods: Two sets of CT images were acquired on each of 21 female patients treated to the left sided breast. In one set the patients were in free-breathing, the other in inhaling-breath-hold. The two image sets have the same coordinate system and are fused in the RayStation5.0.2 treatment planning system. The contours of the heart, breast, and each lung were outlined in the breath-hold image set and then mapped to the free breathing image set. The volume and centroid of each structure were calculated.

Results: The volume and shape of the heart and the breast were basically unchanged from free-breathing to inhaling-breath-hold. The breast displacement vector (mean ± standard deviation) from free-breathing to inhaling-breath-hold was 1.0±0.4 cm in length and (0.1±0.3, 0.9±0.4, 0.4±0.3) cm in the Left-Anterior-Superior 3D system; the heart 1.7±0.6 cm in length and (-0.4±0.3, 0.8±0.4, -1.3±0.7) cm in 3D. The separation of breast-heart was increased by at least 5mm in length for all patients with statistics 1.8±0.7 cm. The movement of the breast is found to be complicatedly correlated with the ratio of the lung volume change.

Conclusion: The geometry of heart, lungs and breast and their displacement were studied for left-sided breast patients from free-breathing to inhaling-breath-hold. Careful setup and tight margin selection for breath monitoring should be in place.


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