ABSTRACT
Objective:To establish a novel clinical application process of the optical surface monitoring system (OSMS) in the cranial frameless stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT), and to assess the accuracy and effectiveness of the OSMS in the intra-fraction motion monitoring of both cranial phantoms and cranial SRT patients fixed using the Q-Fix encompass immobilization system.Methods:The deviations of OSMS in the real-time motion monitoring were assessed by determining the deviations between the displacement of the cranial SRS phantoms detected by the OSMS and the predefined displacement of the Varian Edge six degrees of freedom (6DoF) couch. The ability of the OSMS to conduct real-time monitoring of the head movement was also analyzed when one camera was blocked by the rotary gantry of the accelerator and when the couch was at non-zero angles. Moreover, ten patients who received 50 fractions of cranial frameless SRT were enrolled in this study. All the patients were fixed using the Q-Fix Encompass system, and their intra-fraction motion was monitored using the OSMS. The intra-fraction errors of OSMS real-time monitoring throughout the treatment were obtained from the OSMS logs. The patients received cone-beam computed tomography (CBCT) after the beam delivery, and the six-dimensional errors were obtained as intra-fraction motion errors of the CBCT.Results:For the cranial phantoms, there was a close correlation between the OSMS monitoring deviations and the predefined displacement in six dimensions. The OSMS-detected 3D vector deviations in the translational and rotational directions were (0.28±0.10) mm and (0.15±0.09)°, respectively when the angel both the gantry and couch was 0° and were (0.35±0.13) mm and(0.17±0.09)°, respectively, when one camera was blocked. The OSMS monitoring deviations with the couch at a non-zero degree were greater than those at zero degree. The maximum deviations occurred when the couch was at 270° and were (0.69±0.19) mm and (0.32±0.12)°, respectively, in the translational and rotational directions. For the cranial SRT patients fixed using the Q-Fix Encompass system, the OSMS and CBCT showed comparable intra-fractional motion deviations, which were (0.40±0.26) and (0.29±0.10) mm, respectively in the translational direction and were (0.33±0.20)°and (0.26±0.08)° in the rotational direction.Conclusions:The OSMS is an effective tool for optically guided radiotherapy, which allows for intra-fraction real-time motion monitoring with sub-millimeter accuracy. Therefore, to ensure the accurate preformation of cranial SRS/SRT, it is necessary to conduct the intra-fractional position monitoring using OSMS.
ABSTRACT
Objective:To compare the dosimetric differences between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) on planning target volume (PTV) and organ-at-risk (OAR) for breast cancer after modified radical mastectomy, aiming to provide evidence-based reference for clinical practice.Methods:According to strict inclusion and exclusion criteria, literature search was performed in PubMed, Cochrane Library, FMRS, CNKI, Wanfang Data and VIP full text databases from the inception of databases up to March 2020. The controlled clinical trials of dosimetric comparison between VMAT and IMRT for breast cancer following modified radical mastectomy were selected. The meta-analysis was performed using Stata14 software.Results:The meta-analysis included 281 patients from 13 observational studies. Compared with IMRT, VMAT significantly increased the PTV dose coverage D 95%( P<0.001) and significantly improved the PTV homogeneity index (HI, P<0.001) and conformity index (CI, P=0.004). Compared with IMRT, VMAT more effectively decreased the ipsilateral lung V 20Gy (WMD=1.332, P=0.027) and contralateral lung V 10Gy ( P=0.003). There were no significant differences in theD mean, V 5Gy, V 10Gy and V 30Gy of the ipsilateral lung, D mean and V 5Gy of the contralateral lung, D mean, V 10Gy and V 30Gy of the heart between VMAT and IMRT (all P>0.05). Compared with VMAT, IMRT reduced the cardiac V 5Gy ( P=0.001). However, sensitivity analysis of included literature on cardiac V 5Gy showed that the P value was reversed, indicating that the stability of the results was poor. VMAT significantly shortened the delivery time ( P<0.001) and the number of monitor units ( P<0.001) compared to IMRT. Conclusion:Compared with IMRT, VMAT can achieves superior target dose coverage, HI and CI, better protection for the ipsilateral and contralateral lung, fewer monitor units and shorter delivery time.
ABSTRACT
Objective To investigate the potential heart sparing effects of tangential volumetric modulated arc therapy (T-VMAT) by comparing its dosimetric properties with conventional wedged tangential fields (W-TF) technique and 6-field intensity-modulated radiotherapy (6F-IMRT) in the locoregional radiotherapy of left breast cancer after conserving surgery,including internal mammary nodal irradiation.Methods Fifteen patients with left breast cancer were enrolled in this study.Three plans were generated for each patient:W-TF,6F-IMRT and T-VMAT with two arc segments of 50°.The prescription dose to planning tumor volume (PTV) was 50 Gy in 25 fractions.Dose-volume parameters and indices of conformity were calculated and compared for the PTV and organs at risk (OAR).Results Compared with W-TF,T-VMAT not only significantly decreased D D and the high dose areas (above 10 Gy) of the heart and left anterior descending branch (LAD) (P ＜ 0.05),but also had the trend of sparing the V5Gy although there was statistically significant difference (P ＞ 0.05).T-VMAT also significantly decreased Dmean V5Gy,V10Gy and V20Gy of the heart,as well as the D V5Gy and V10 Gy of LAD (P ＜ 0.05),compared to 6F-IMRT.Furthermore,T-VMAT did not result in higher V20Gy of ipsilateral lung and higher V5Gy of contralateral breast compared with W-TF (P ＞ 0.05).T-VMAT achieved distinctly better target coverage and conformity,meanwhile obviously lowered hot volume of V110 compared to W-TF (P ＜ 0.05).Conclusions T-VMAT not only significantly decreased the high dose areas,but also had the trend of sparing the low dose area for the heat and LAD.Moreover,there was no significant difference for V20Gy of ipsilateral lung and V5Gy of contralateral breast between T-VMAT and W-TF.