Analysis Of Whole Breast Displacement Relative To Selected Skin Markers And Surgical Clips Using Four-Dimensional Computed Tomography

Objective: To explore the relationship between the displacement of the whole breast target and the displacement of a selected skin marker, the nipple and a selected surgical clip using four-dimensional computed tomography (4DCT). Methods and materials: Thirteen breast cancer patients who had undergone breast-conserving surgery were recruited for whole breast intensity-modulated radiotherapy (IMRT), and respiration-synchronized 4DCT image data were gathered during free breathing. The correlation between the displacement of the whole breast and the displacement of the clip, nipple and skin marker were analyzed. The changes in ipsilateral lung volume were analyzed during the respiratory cycle relative to the displacement of the breast. Results: There was no significant difference between the volumes of the whole breast targets at the selected end-inspiration (EI) and end-expiration (EE) phases. No meaningful correlation established between the breast and lung volume variance with the target motion. According to a population-based analysis, the displacement of the whole breast target was only significantly associated with the displacement of the superior clip along the Y-axes (r = 0.657, P = 0.015). Conclusion: The changes in breast and lung volume cannot be used to identify the target displacement. The selected clip in the surgical cavity may serve as a useful surrogate for tracking whole breast target movement during radiotherapy.