A Study on the Displacements of the Clips in Surgical Cavity for External-beam Partial Breast Irradiation after Breast-conserving Surgery Based on 4DCT

Abstract

To explore the clip and the geometrical center displacements based on the four-dimensional computed tomography (4DCT) for external-beam partial breast irradiation (EB-PBI), fourteen breast cancer patients treated with breast-conserving surgery were recruited for EB-PBI and undertook 4DCT simulation during free breathing. The displacements of the selected clips and the geometrical center at left-right (LR), anterior-posterior (AP) and superior-inferior (SI) directions were measured. The comparison and the correlation of the displacement between the selected clips and the geometric center were analyzed. The displacements in AP and SI were greater than that in LR for the same selected clip (P < 0.05). Almost all the displacements of the geometrical center were greater than that of the selected clips in the same direction, (P < 0.05), except the displacements of lower clip in SI direction. The displacement of the geometric center showed a statistical correlation with the upper clip and lower clip in SI direction (both P < 0.05). Therefore, the internal margin in AP and SI directions should be greater than LR direction for the purpose of adequate target coverage and sparing more normal tissue. This study also indicates that the displacement of a single clip was not qualified to substitute for the displacement of the target based on all clips of the surgical cavity.

Displacement of the lumpectomy cavity defined by surgical clips and seroma based on 4D-CT scan for external-beam partial breast irradiation after breast-conserving surgery: a comparative study

“…Of the 19 studies, surgical clips and gold fiducial markers were used as references in measuring the displacements in 11 studies. In this study, the 3D displacements of selected clips were similar to those in previous studies [17,23]. Based on 4D-CT, Wang et al [17] reported that the intrafraction displacements in the LR, AP and SI directions were 0.460.…”

“…The displacement magnitude of the clip COM in this study was similar to the results acquired by Wang et al [17], who applied 4D-CT to explore the displacement for EB-PBI and reported that the displacements of the geometric (consisting of all the surgical clips) centre in the LR, AP and SI directions were 1.460.4, 2.06 1.0 and 1.961.0 mm, respectively. We found that in the 3D directions, the similar displacements of the clip COM were significantly larger than those of the GTV c , GTV s , GTV c1s .…”

“…Although the displacements of the target volume delineated based on clips and seroma have been obtained using 4D-CT in prior studies [16,17], the displacement differences among target volumes have not been fully illustrated. In order to investigate the displacement differences among the target volumes delineated based on clips and/or seroma, we measured and compared the three-dimensional (3D) displacements among three target volumes, the centre of mass (COM) of all the surgical clips and four selected boundary clips during free-breathing (FB).…”

“…The majority of similar studies have measured the respiratoryinduced displacement of GTV delineation based on the surgical clips [11,17,18]. How to outline the GTV based on the scattered clips in the lumpectomy cavity remains to be established, and the volumetric nature of the cavity may not be accurately reflected.…”

“…Four-dimensional CT (4D-CT) simulation has enabled CT data acquisition to be correlated with the respiratory cycle. Therefore, 4D-CT was pervasively used in delineating the target volume and forming the internal target volume (ITV) for EB-PBI [16,17]. …”