ObjectiveTo investigate the clinical feasibility of optical surface imaging (OSI) system in guiding thermoplastic body film to fix radiotherapy of pelvic tumors.MethodsFrom January to May in 2019, 20 pelvic tumor patients fixed with thermoplastic films were selected. After the first treatment, cone beam CT (CBCT) was performed to verify and correct the setup errors. OSI was used to collect the patient’s image information as the reference image for the later treatment setup. The later treatment was performed by traditional three-point setup, and OSI was used to record the setup data and monitor the treatment. CBCT scan results were taken as the standard, to calculate the system error (Σ), random error (σ) and margin of three-point and OSI setup. The result of CBCT scan was defined as three-point setup error.ResultsIn lateral-medial, superior-inferior, and anterior-posterior directions, the OSI system errors were 0.14, 0.37, and 0.14 cm, respectively, the random errors were 0.20, 0.57, and 0.23 cm, respectively, and the corresponding margins were 0.49, 1.32, and 0.51 cm, respectively; the three-point setup system errors were 0.13, 0.39, and 0.12 cm, respectively, the random errors were 0.15, 0.43, and 0.13 cm, respectively, and the corresponding margins were 0.43, 1.28, and 0.39 cm, respectively. If the target coverage rate was counted at the 0.8 cm outward margin, the proportions of the three-point setup in lateral-medial, superior-inferior and anterior-posterior were 100.00%, 80.65%, and 100.00%, respectively, and those of the OSI setup were 100.00%, 95.48%, and 99.35%, respectively. Pearson analysis showed that the weakly correlation of lateral-medial, superior-inferior directions had statistical significance (P<0.05), and there was no statistical significance in the other directions (P>0.05).ConclusionsCompared with the traditional three-point setup, OSI cannot improve the setup precision of thermoplastic body film fixation in pelvic tumor radiotherapy. OSI acquired the image of thermoplastic phantom, which is quite different from the actual target location of the patient. OSI application method should be improved in clinical application.
This paper aims to propose a noninvasive radiotherapy patient positioning system based on structured light surface imaging, and evaluate its clinical feasibility. First, structured light sensors were used to obtain the panoramic point clouds during radiotherapy positioning in real time. The fusion of different point clouds and coordinate transformation were realized based on optical calibration and pose estimation, and the body surface was segmented referring to the preset region of interest (ROI). Then, the global-local registration of cross-source point cloud was achieved based on algorithms such as random sample consensus (RANSAC) and iterative closest point (ICP), to calculate 6 degrees of freedom (DoF) positioning deviation and provide guidance for the correction of couch shifts. The evaluation of the system was carried out based on a rigid adult phantom and volunteers’ body, which included positioning error, correlation analysis, and receiver operating characteristic (ROC) analysis. Using Cone Beam CT (CBCT) as the gold standard, the maximum translation and rotation errors of this system were (1.5 ± 0.9) mm along Vrt direction (chest) and (0.7 ± 0.3) ° along Pitch direction (head and neck). The Pearson correlation coefficient between results of system outputs and CBCT verification distributed in an interval of [0.80, 0.84]. Results of ROC analysis showed that the translational and rotational AUC values were 0.82 and 0.85, respectively. In the 4D freedom accuracy test on the human body of volunteers, the maximum translation and rotation errors were (2.6 ± 1.1) mm (Vrt direction, chest and abdomen) and (0.8 ± 0.4)° (Rtn direction, chest and abdomen) respectively. In summary, the positioning system based on structured light body surface imaging proposed in this article can ensure positioning accuracy without surface markers and additional doses, and is feasible for clinical application.