Abstract:

Objective To investigate the auxiliary positioning function of optical body surface imaging in styrofoam⁃fixed breast⁃conserving intensity⁃modulated radiotherapy and the influence of observation area on the posi⁃ tioning. Methods A total of 34 breast cancer patients who received intensity⁃modulated radiation therapy in Sun Yat⁃sen University Cancer Center from May 2020 to July 2021 were selected. The position was set according to the marking line of the body surface，and then corrected by the optical body surface monitoring system（C ⁃RAD Catalyst HD），finally the position was verified by cone beam CT（Cone Beam CT，CBCT）. The region of interest （ROI）in C⁃RAD Catalyst HD was divided into single⁃affected ROI and bilateral ROI. The treatment bed value after positioning according to the marking line，and Catalyst HD correction were recorded separately，and the set⁃up errors by CBCT were also recorded. The set⁃up errors according to the marking line of the body surface with the set⁃ up errors of Catalyst HD，the set⁃up errors of the single⁃affected side ROI with the set⁃up errors of the bilateral ROI were analyzed by t test. Results The set⁃up errors by the marking line of the body surface and C⁃RAD Catalyst HD in the left and right，head⁃foot，and abdominal⁃back directions were（2.21 ± 2.14），（2.46 ± 2.22），（3.33 ± 2.43）mm and（1.42 ± 0.99），（1.31 ± 0.86），（1.38 ± 1.06）mm respectively（LR：t = -3.473，SI：t = -4.95，AP： t = -3.438，all P < 0.05）. The three⁃dimensional linear errors of single⁃affected ROI and bilateral ROI in the left⁃ right，head⁃foot，and abdominal⁃back directions were（1.59 ± 1.23），（1.41 ± 1.02），（1.50 ± 0.93）mm and（1.71± 1.22），（1.89 ± 1.29），（1.31 ± 1.71）mm respectively；three ⁃dimensional rotation errors were［Rtn：（0.53 ± 0.49）°，Roll：（0.77 ± 0.75）°，Pitch：（0.71 ± 0.68）°］and［Rtn：（0.45 ± 0.49）°，Roll：（0.95 ± 0.75）°，Pitch： （0.71 ± 0.69）°］respectively（AP：t = 0.005，Roll：t = 0.003，P < 0.05）. Conclusion Catalyst HD can improve the positioning accuracy of intensity ⁃modulated radiotherapy after breast ⁃conserving breast cancer with assisted styrofoam fixation. It is recommended to choose bilateral ROI when selecting the region of interest monitored by the Catalyst HD.

Key words:

breast cancer, intensity?modulated radiotherapy, optical body surface monitoring system, set?up error