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Objective:To explore the application value of skin lead marker combined with iSCOUT image-guided positioning system in monitoring and correcting the setup error of intensity-modulated radiotherapy (IMRT) for breast cancer and calculate the PTV margin, aiming to provide reference for clinical practice.Methods:25 breast cancer patients treated with IMRT after modified radical mastectomy in Fujian Medical University Union Hospital from April to August 2019 were enrolled in this study. The skin lead marker combined with iSCOUT image-guided positioning system was employed for image-guided positioning based on the gold standard registration algorithm. Initial setup errors on the x (lateral), y (craniocaudal) and z (anteroposterior) axis and residual errors after the position correction were recorded and analyzed. The effect of the errors before and after image-guided correction upon the plan dose was compared and the reasonable PTV margin was calculated.Results:25 patients received 150 times of positioning verification using skin lead marker combined with iSCOUT image-guided positioning system. The absolute residual errors on the x-, y-and z-axis were (1.53±0.96), (1.30±0.99) and (1.34±0.92) mm, significantly smaller than the initial setup errors of (2.63±2.12), (2.41±2.45) and (3.07±2.77) mm (all P<0.001). The percentage of dose deviation due to residual errors was also smaller than that of the initial errors. Significant differences were observed in D 98%, D 2%, D max of PTV, D max of the heart, D max of the healthy breast, and D mean of the affected lung and both lungs. The percentage deviation from the original plan was decreased from 2.18%, 3.19%, 10.66%, 8.75%, 48.21%, 10.50%, and 3.66% to 0.38%, 0.23%, 2.31%, 0.04%, 13.78%, 6.35% and 0.41%, respectively (all P<0.05). PTV margins on the x-, y-and z-axis after correction were calculated as 1.87, 1.75 and 1.69 mm, respectively. Conclusion:It is feasible and valuable to apply the skin lead marker combined with iSCOUT image-guided positioning system in the positioning verification and correction of breast cancer radiotherapy position, providing novel reference for clinical PTV margin.
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Objective:To develop a remote training system for CT simulation positioning of radiotherapy using virtual reality technology, and to explore a new method of medical training.Methods:The 3DMax and Maya were employed to establish the 3D model. The unity3D engine was adopted to develop 3D virtual operation and interaction system. Java spring MVC architecture was utilized as the system background service. MySQL was used as the background database system. The users were assigned into two roles: teacher and student, and the modes were divided into teaching and assessment modes.Results:The function of the system covered the whole process of CT simulation positioning, mainly including modules of patient information management, CT simulation positioning machine cognition, body position fixation technology, CT positioning scanning, and emergency handling, etc. Since it was put into use in 2018, the system has been running stably, with 14 920 pages views and an 86.66% pass rate. Compared with the traditional training, the training efficiency has been significantly improved and has received unanimous recognition.Conclusions:The remote training system can effectively improve the clinical practice ability and humanistic care ability of the trainees, which has good autonomy, sharing, and innovation. At present, the system has been put online and has strong popularization with prospects for broad application.
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Objective To analyze the effect of the new conformal index(nCI)and the conventional conformal index(CI)on the treament planning quality of lung stereotopic radiotherapy(SBRT).Methods A total of 19 peripheral lung cancer patients,treated with SBRT in Fujian Medical University Union Hospital from 2014 to 2017,were analyzed retrospectively.Each patient was planned twice yielding identical CI and nCI.The prescription to 95％of planning target volume(PTV)was 48 Gy in four fractions,and renormalization was performed when needed for nineteen nCI plans.The Wilcoxon signed-rank test was used to examine the dosimetric index.Results The dose conformity plots indicate that nCI does not only reflect the dose to the organ at risk outside tumor,but also represents the dose distribution in the PTV.In addition,nCI was stricter with treatment planning qualities when the dose around PTV was closer to the prescribed dose.The value of target coverage(TC),the ratio of out-of-target volumes receiving 105％prescribed dose to the target volume(R105％),the ratio of volume covered by 50％isodose line to the target volume(R50％),and the ipsilateral lung V20were 98.70％,0.56,5.53,15.59％in the CI plans,vs.90％,0,4.99,14.42％in the corresponding nCI plans,respectively.All index were significantly lower in the nCI group(Z ＝-3.823,-3.180,-3.823,-3.783,respectively,P＜0.05).The ratio of the maximum dose to the 2 cm external margin from the PTV(D2 cm)to the maximum dose to the PTV were 63.70％and 64.07％respectively in the two groups,and the differences were not statistially significant(P＞0.05).The conformity values denoted a clinically favorable value as 1 between D95％and D99％of nCI plans,yet were not applicable to CI plans.Conclusions It is more clinically relavant to evaluate lung SBRT plans using nCI,TC and other indicators collectively than using CI alone.
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Objective To investigate the dosimetric performance of two algorithms for correcting the presence of tissue inhomogeneities,the finite site pencil beam (FSPB) and X-ray voxel Monte Carlo (XVMC) plans were implemented in the MONACO system,with the accuracy of application to clinic treatment of two algorithms were evaluated.Methods In a non-uniform artificial anthropomorphic phantom,regular open fields and intensity modulation radiated therapy (IMRT) plans of the MONACO were measured by using calibrated EBT2 films,and the dose accuracy of the two kinds of plans was analyzed by comparing the planned and measured plane dose.Results In an anthropomorphic phantom,the deviations between the calculated values by XVMC and the measured values by films were less than ± 2％.While the deviations of FSPB values between calculation and measurements was within ± 3％,except at the condition of 15 MV,10 cm ×2 cm field,the dose error in lung was up to 6.51％.The verification of individual IMRT beams based on films showed that the pass rates of calculation by XVMC and FSPB were larger than 90％ with γ criterion of 3％/3 mm and 4％/4 mm,respectively.At 3％/3 mm,the pass rates of FSPB were in the range of 80％-90％.At the same time,the pass rates of all individual fields were higher than 90％.Conclusions The accuracy of dose calculation of XVMC is better than that of FSPB when being in multi-segments and non-uniform media.The error of algorithm can be controlled within ±3％,for the calculation by XVMC.And the dose deficiency of PTV arising from algorithm can be avoided.