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Objective:To investigate the impact of carbon based non-conductive sliding rails on intensity-modulated radiation therapy (IMRT) planning for vertebral tumors.Methods:A reconstruction imaging of the couch plate and its rails removed from the EDGE linear accelerator was acquired by helical computed tomography (CT), and pushed into the treatment planning system (TPS). Based on CT images of homogeneous phantom and patients in our database, 6 and 10 MV photon IMRT plans were designed with five fields (180°, 200°, 220°, 160°, 140°), setting a prescribed dose of 3 Gy/F ×10 F to the planning target volume (PTV), and the dose was calculated by AcruosXB. In addition, optimization plans (OP) without rails and with rails symmetrically moving (4-19 cm, step size 1 cm) were created and verification plans(VP) were created by inserting and removing slide rail′s structure from the corresponding OP in VP. The differences in mean dose ( Dmean), homogeneity index (HI), and conformability index (CI) of the PTV, and maximum dose ( Dmax) of the spinal cord were compared and analyzed between the VP and OP. Results:HI of PTV with and without the rails were worse in the 6/10 MV verification plans, with a maximum difference of 2%. In 6 MV plans, with rails Dmean of PTV decreased by (2.07±0.99)%, CI increased by (4.91±3.12)%, and Dmax of spinal cord decreased by (1.83±1.37)%. Without rails, the Dmean of PTV increased by (2.02±0.96)%, but CI decreased by (3.07±1.31)% and Dmax of the spinal cord increased by (2.03±1.44)% in the patient respectively. There were significant statistical differences between groupswith and without rails( F=27.55, 361.32, 13.05, P<0.05). The target volume Dmean and spinal cord Dmax decreased with a sloping " W" with the change of the rail position. The difference appeared to be noticeable in the range of less than 10 cm, but it gradually decreased as the rails slid to the outside until it reached zero, and the Dmean of PTV and Dmax of the spinal cordchanges were less in 10 MV plans, comparing to 6 MV plans. Conclusions:The dose attenuation by the sliding rails of the Qfix kVue should not ignored in the IMRT of spinal metastases and the slide position should be consistent with the planned position.
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Objective:To evaluate the difference of dosimetry between three-dimensional and two-dimensional plans based on CT images of occult perforation in brachytherapy of cervical cancer, aiming to provide clinical reference.Methods:A total of 817 patients with cervical cancer received simple intrauterine (intrauterine tandem plus vaginal colpostats) three-dimensional brachytherapy in Chongqing University Cancer Hospital from January 2019 to December 2020 were retrospectively reviewed. Among them, 16 patients had occul uterine perforation. Based on Oncentra Brachy Therapy plan system, the single prescription dose was 6Gy. Three-dimensional (3D group) and two-dimensional (2D group) plans were designed on the perforated CT images The target volume, conformal index (CI), conformal index coformity index (COIN) and organs-at-risk (OAR) D 2cm 3 parameters were used to assess the plans between two groups. Results:The incidence of pccult uterine perforation was 1.96%(16/817) during brachytherapy for cervical cancer. The volume of prescription dose curve in the 3D group was (40.74±14.98) cm 3, significantly smaller compared with (91.46±19.71) cm 3 in the 2D group ( P<0.05), whereas the volume of the high-risk clinical target area wrapped by prescription dose curve did not significantly differ between two groups ( P>0.05). The CI and COIN in the 3D group were 0.79±0.10 and 0.72±0.96, significantly higher compared with 0.38±0.09 and 0.37±0.18 in the 2D group (both P<0.05). The D 2cm 3 of bladder, rectum, sigmoid colon, small intestine in the 3D group were (306.06±77.57) cGy, (252.27±72.60) cGy, (127.25±62.84) cGy and (228.79±94.90) cGy, significantly lower than (548.03±164.21) cGy, (411.16±118.74) cGy, (227.45±94.48) cGy and (450.95±157.96) cGy in the 2D group (all P<0.05). Conclusions:Application of image guidance in brachytherapy of cervical cancer is helpful to detect occult uterine perforation. When occult uterine perforation occurs, the use of three-dimensional plan can basically meet the clinical needs, which is significantly better than the two-dimensional plan.
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Objective:To monitor and evaluate in vivo dose changes of intensity-modulated radiotherapy (IMRT) in patients with cervical cancer in a real-time manner. Methods:Twelve patients with cervical cancer admitted to our hospital were enrolled in this study. The in vivo doses were monitored by PerFRACTION?. Electronic portal imaging device (EPID) were collected in each treatment fraction for two-dimensional in vivo dose verification[γ index and dose difference (DD) index]. Log files were recorded for three-dimensional in vivo dose verification (γ index). The correlation between in vivo dose and treatment duration was analyzed by Pearson correlation analysis. Results:A total of 206 sets of EPID images and corresponding Log files were collected. The three-dimensional in vivo dose verification γ 1%/1mm of all patients was not correlated with treatment fraction ( P>0.05). Among them, the absolute difference of γ 1%/1mm of 94.66% fractions was< 1%. The mean DD 3% of two-dimensional in vivo dose verification of all patients was negatively correlated with treatment fraction ( P<0.05). Among which, the average γ 3%/3mm of 9 patients was>89% in the treatment fractions, and the average γ 3%/3mm of 98.57% fractions of these 9 patients was>93%. The other 3 patients had an average γ 3%/3mm ranged from 38% to 100%. CBCT images showed that the bladder volume of these 3 patients was significantly decreased with the relative changes by 82.08%, 84.41% and 73.59%, respectively, and the target area was retracted significantly with the relative changes by 38.12%, 59.79% and 24.46%, respectively. Conclusion:Combined with γ index and DD index, PerFRACTION? can monitor the mechanical stability of accelerator and MU delivery accuracy during treatment fractions, and monitor the changes of in vivo dose in patients with cervical cancer, which can improve the safety and quality assurance of IMRT for cervical cancer patients and provide guidance for patients with adaptive radiotherapy.
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Objective To study the effect of the uncertain deflection of the Delta4 phantom (ScandiDos AB,Sweden) in setting up on the Gamma index passing rate during the VMAT plan verification.Methods Two patients with head and neck cancer,two with lung cancers and one with pelvic cancer receiving VMAT radiotherapy were randomly chosen.By means of Eclipse8.6 TPS the treatment plans elaborated for the five patients were picked up to make the verification plans and Delta4 was used to perform dose verification On VARIAN Clinac Ⅸ.The Delta4 phantom was precisely set up first,and then it was deflected in a given angle towards the horizontal direction in relation to the center of the linear accelerator isocenter to perform the dose verification for 11 times successively.To figure out the relationship between the deflection angle of the Delta4 phantom and the Gamma index passing rate.Results As the Delta4 phantom was deflected by 0.0°,0.2°,0.4°,0.6°,0.8°,1.0°,1.2°,1.4°,1.6°,1.8° and 2.0° in sequence,the measured Gamma index passing rates presented a slight decline,but all greater than 90％ (DD 3％,DTA 3 mm).Conclusions In the VMAT plan verification,the Gamma index passing rate of Delta4 has no dependence on the uncertain deflection of the Delta4 phantom provided that the uncertain deflection of the Delta4 phantom is no greater than 2°,but the passing rates of DD and DTA vary significantly with the uncertain deflection of the Delta4 phantom.
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High intensity focused ultrasound (HIFU) is a very complex transient process and can cause tissue coagulation necrosis. The cavitation and boiling behaviour of bubbles in the focal region play very important roles throughout an injury process. This paper reviews the research done by domestic and foreign scholars on behaviours of bubbles in HIFU irradiation process and summarizes in the focal region bubble cavitation and boiling generation, related detective means and relationships with hyperecho, temperature rise of the focus and injury shape.