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Objective:To reconstruct the dose of nasopharyngeal carcinoma and verify the results of the whole-process radiotherapy plan based on log files and cone beam CT (CBCT).Methods:A total of 15 patients with nasopharyngeal carcinoma who received volumetric modulated arc therapy (VMAT) with Halcyon accelerator in the Cancer Center of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology from February to September 2022 were retrospectively selected. Log files and CBCT for all fractionated radiotherapy were recorded. The errors of monitor unit (MU), gantry angle, and multi-leaf collimator (MLC) leaf position per control point were analyzed. The adaptive CT (aCT) were generated according to CBCT and planned CT (pCT) using a commercial software Velocity TM, and the similarities among aCT, pCT and CBCT were analyzed. The original plan was modified from the log files and imported into the treatment planning system to calculate the delivered dose on the corresponding fractionated aCT to reconstruct the fractionated dose. And all the reconstructed doses were mapped back to pCT to obtain the cumulative dose. Theγpass ratios with criteria of 2 mm/2% and 2 mm/3% and the dose differences between the planned dose and the cumulative dose in the planning target volume (PTV) and organs at risk (OAR) were compared. Results:The root mean square (RMS) and the 95th percentile of the errors of MU, gantry angle and MLC leaf position errors were within an acceptable range. The aCT generated by Velocity TM had the anatomical structure of CBCT and the resolution, contrast, noise characteristics of pCT, which could be directly used for dose calculation. Compared with the planned dose, the changes of V 70 Gy of nasopharyngeal primary tumor (PTV nx), V 68 Gy of cervical glands (PTV nd) and V 60 Gy of planning target volume (PTV1) were -0.88%±1.91%, -2.99%±2.99% and -0.63%±0.93%, respectively, and V 40 Gy of parotid gland was increased to 2.65%±2.63%. Cumulative dose showed different degrees of PTV dose decrease ( P<0.05) and parotid dose was increased ( P<0.05). The γ pass ratio (2 mm/3%) between the cumulative dose and planned dose was 97.3%±2.7% and >95.0% in 86.7% of patients. Conclusions:Based on the log files and CBCT, the whole-process dose reconstruction of nasopharyngeal carcinoma patients can be carried out. According to the results of dose reconstruction, the radiotherapy effect of the target area and OAR can be quantitatively evaluated. In the case of high dose coverage and conformity of the original plan, the reconstruction results show that the cumulative dose coverage of the target area is decreased, whereas that of the parotid gland is increased.
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Objective:By comparing the comprehensive differences between volume-modulated arc therapy (VMAT)-and CyberKnife-6D Skull (CK-6D Skull) tracking technology-based stereotactic radiotherapy (SRT) plans in the treatment of multiple brain metastatic tumors, and explore the advantages of multi-target intracranial technology.Methods:Clinical data of 42 patients with more than 2 brain metastases who received STR between January 2017 and August 2018 were retrospectively analyzed. For each patient, two radiotherapy plans were designed by selecting CK-6D Skull and VMAT technologies. The quality of VMAT and CK-6D Skull was compared by calculating the gradient index (GI), dose sag volume and organ at risk (OAR) of target area. The total number of monitor unit and single treatment time were recorded to compare the execution efficiency of these two technologies.Results:The GI of intracranial 2-target and 3-target plans of CK-6D Skull technology was significantly superior to that of VMAT technology ( P<0.05). The GI did not significantly differ between the 4-target and the 5-target groups ( P>0.05). The contribution of these two technologies to the maximum dose of OAR was not significantly different ( P>0.05), whereas the treatment time of VMAT technology was shorter ( P<0.05). Conclusions:Both technologies can meet the requirements of clinical SRT for multiple brain metastatic tumors. From the perspective of treatment plan and implementation, SRT based on CK-6D skull technology is recommended for patients with less than 4 intracranial metastatic tumors, and VMAT-based SRT is considered for those with > 4 metastatic tumors. Patients with poor physical condition and difficulty in maintaining a fixed position for a long time shall give priority to VMAT technology. More differences between these two technologies in the implementation of SRT for intracranial multiple brain metastases remain to be elucidated by more case data for statistical analysis.
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Objective To explore the clinical value of an auxiliary set-up method with fiducial markers and Synchrony tracking implanted in spine during Cyber-knife stereotactic radiotherapy by comparing the rotational setup errors between auxiliary setup with less than and more than three fiducial markers.Methods A total of 145 cases of tumor patients with fiducial tracking and Synchrony tracking were selected for radiotherapy,including 94 cases in the observation group (＜3 fiducial markers) and 51 cases in the control group (≥ 3 fiducial markers).Before treatment,one spinal alignment plan was added to all the cases in the observation group,and the rotation deviation of the selected spinal distance and the assisted spinal alignment correction of the fiducial marker tracking and the fiducial marker respiratory tracking were counted respectively,and the result of the rotation deviation calculated in the observation group and the control group were analyzed.Results Fiducial tracking spine auxiliary setup result:fiducial marks and selected the spine center distance ＜ 20,20-40,40-60,60-80 and ＞ 80 mm rotating statistical average deviation (0.494±0.350) °,(1.291±0.590) °,(1.705±0.739) °,(2.512±0.761) ° and (2.796± 1.081) °,respectively,rotate observation group and control group total deviation (1.742±0.784) °,(1.805±0.562) °,respectively.Synchrony tracking result in the above case rotation statistical average deviation was (1.190± 0.547) °,(1.956± 0.735) °,(2.141 ± 0.670) °,(2.957±0.648) ° and (4.027±0.695) °,respectively,while rotation total deviation in observation group and control group (2.619±0.906) °,(2.233 ±0.763) °,respectively.There was no significant difference in the rotation deviation between the assisted spinal set-fup and the calculation of rotation deviation between the fiducial tracking and the synchrony tracking (P ＞ 0.05).Conclusions In the fiducial tracking treatment,the range of rotation deviation for the spinal auxiliary set-up correction increases with the increase of the distance between the fiducial markers and the selected spinal center.When the distance between the fiducial marker and the selected spinal is less than 60 mm,the rotation deviation calculated by the spinal auxiliary setup has the same tumor rotation correction effect as that calculated by the fiducial markers.When less than 3 fiducial markers are available and the minimum distance between the fiducial marks and the center of the adjacent spine is relatively close (＜ 60 mm),the deviation of the rotation direction of the tumor can be calculated by adding the spinal auxiliary setup plan.
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Objective@#To improve synchrony tracking components of CyberKnife (tracking vest and tracking markers) and to analyze the clinical application value of the improved tracking components in CyberKnife treatment of thoracic and abdominal tumors.@*Methods@#The tracking apron was made of knitted four-side elastic spandex cloth and suture design of Velcro, which was used to stick the tracking markers on the chest and abdomen of patients. The tracking markers added a 2 cm thick light foam block to the bottom of the original markers, and then the hook face of the Velcro was fixed to the bottom of the light foam. The improved trace component (the improved component) and the original component (the vendor component) were applied to the lung tracking treatment model, and the manufacturer components were included in the reference group. Adoption of improved components into the observation group; 20 different types of respiratory waveforms were simulated and applied to the same mold plan. After treatment, the coverage rate, mean standard deviation, maximum standard deviation and the slope of XYZ-axis vs. R correlation graph were recorded. The relevant parameters of Synchrony model and wearable time of two components were compared, and the application significances of the improved tracking component in the breathing tracking process of the CyberKnife were evaluated.@*Results@#The maximum slope [median(interquartile range)] of XYZ-axis vs. R related graph in the reference group was 0.73 (3.89), 0.27 (0.49) and 0.34 (1.02), respectively. The maximum slope of XYZ-axis vs. R related graph in the observation group was 0.70 (2.78), 0.31 (0.30) and 0.36 (0.75), respectively. There was no statistically significant difference in the slope of XYZ-axis vs. R between the reference group and the observation group (all P > 0.05). There was no significant difference in the average standard error and maximum standard error between the reference group and the observation group [(1.7±0.4) mm vs. (1.7±0.5) mm, t=-0.382, P= 0.710; (2.0±0.6) mm vs. (1.7±0.5) mm, t=-0.877, P= 0.401], and the difference of the model coverage rate between the two groups was statistically significant [(48±18)% vs. (60±22)%, t= 2.762, P= 0.042]. The setup time of tracking components in the observation group was less than that in the reference group, and the difference was statistically significant [(44±24) s vs. (81±15) s, t=-4.310, P= 0.001].@*Conclusions@#The improved tracking components are comparable to the manufacturer tracking components in the standard error of the Synchrony model. The improved components shorten the wear time and appropriately improve the coverage of the Synchrony model.
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Objective To investigate the impact of four different collimator angle optimization techniques on the planning target volume (PTV) and organ at risk (OAR) during intensity-modulated radiotherapy (IMRT) for gastric cancer.Methods Ten patients with gastric cancer undergoing IMRT in Zhongnan Hospital of Wuhan University from 2015 to 2016 years were recruited in this study.All IMRT plans were designed by conventional five fields (330°,10°,45°,90°and 180°).In the Eclipse treatment planning system,four different collimator angle optimization techniques with consistent planning optimization parameters were employed to design the IMRT plan.Collimator angle optimization techniques included the following aspects.The collimator angle was set at 0 degree (CL0),collimator angle was set at 90 degree (CL90),Eclipse automatic collimator angle optimization (CLA) was adopted and collimator angle was set as the angle when the distance between X-Jaws and PTV (CLx) was the shortest.The dosimetric parameters mainly included the conformal index (CI) of PTV,the homogeneity index (HI),the mean dose (Mean),and the dosage of OAR.The treatment time (Time),monitor unit (MU),control point (CP),split field (SF) and conformal distance (Fx) were also considered.Results Regarding CL0 as the control,the CI,HI and Mean did not significantly differ among four collimator angle optimization techniques (all P＞0.05),whereas CLx could significantly increase the average dose of PTV in the target area (P＜0.05);CLx optimization reduced the liver (V30 reduction by 1.54％),left kidney (V12 decrease by 1.46％),right kidney and other OARs,whereas it slightly increased the maximum dose of the small intestine and spinal cord (＜1％).CLgo and CLA optimization elevated the dose of OAR in gastric cancer.Among four different collimator angle optimization techniques,CLx optimization reduced the MU (25.02％),CP (26.03％),Fx (20.27％) and SF (by 1.3separate fields on average) and treatment time (10.03％).CLgo and CLA optimization could decrease the MU,CP,Fx and SF.CL90 optimization had certain advantages in shortening the treatment time,whereas CLA optimization could prolong the treatment time by 5.04％.Conclusions During IMRT for gastric cancer,CL90,CLA and CLx collimator angle optimization techniques can obtain comparable dosimetry distribution to CL0 optimization technique,which can reduce the MU,decrease the radiation leakage,shorten the treatment time and improve treatment efficiency.
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Objective To evaluate the effect of the discrepancy of the dose calculation results of different algorithms upon the CyberKnife lung tumor treatment plan,and assess the impact of tumor volume and location on the dose calculation results. Methods Thirty-two cases of lung tumors were treated with MultiPlan 5.2.1 planning system of CyberKnife VSI.Ray Tracing and Monte Carlo algorithms were adopted to calculate the dose distribution, and then the calculation results were statistically compared between two algorithms. Results For the enrolled cases,the calculation results of these two algorithms demonstrated that the deviation range of prescription dose coverage of planning target volume (PTV),conformal index,new conformal index and uniformity index were 0.93%~68. 80%, 0.87%~17. 21%,-212.38%~8. 27% and 0%~15. 17%, respectively. Conclusions In the CyberKnife treatment of lung tumors, the volume and location of tumors exert significant impact on the discrepancies of the dose calculation results of different algorithms. The smaller tumor volume and longer beam heterogeneity path are likely to generate a greater discrepancy. It is recommended to adopt or refer to the calculation results of Monte Carlo algorithm to deliver corresponding treatment.
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Objective To evaluate the effect of ion chamber sensitive volume on absolute dose verification in CyberKnife plan.Methods Solid water phantoms were scanned by a CT scanner, single-field plan, multi-field isocentric plan and sequential optimized plan were designed by the treatment planning system.Absolute doses were measured at the specified point in each plan using the ion chambers with sensitive volumes of 0.007 cm3(A16), 0.24 cm3(A12 s), and 0.6 cm3(PTW30013) and compared with calculated values.Results For the single-field plan, the relative error increased as the aperture size of collimator decreased;with relative errors within ±2%, the smallest aperture sizes of collimator were 12.5 mm (A16), 25 mm (A12 s), and 30 mm (PTW30013).For the multi-filed isocentric plan, the relative errors were 0.26%±3.90%(A16),-6.28%±14.33%(A12 s), and-9.41%±14.10%(PTW30013).For the sequential plan optimized with 15 mm cone, the relative error was 0.79%±1.43%;for the sequential plan optimized with 7.5 mm cone, the relative error was 2.01%±8.39%.In absolute dose verification for clinical plans, there was no significant difference between the results measured by these ion chambers (P=0.985).Conclusions There is no significant effect of ion chamber sensitive volume on absolute dose verification in CyberKnife plan under the following two situations:(1) the collimator with a relatively large aperture is used;(2) the sensitive volume of ion chamber is totally covered by the prescription isodose line.
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Objective To conduct a computer simulation to evaluate the discrepancy between the cumulative doses calculated by four-dimensional computed tomography (4DCT) images and 4DCT scans (for real-time respiratory motions) due to the patient's irregular breathing.Methods A series of digital phantoms were generated from a patient's 4DCT images to simulate 4DCT images and 4DCT scans (for real-time respiratory motions) resulting from various irregular breathing curves.A six-field intensity-modulated radiotherapy plan was generated.Two cumulative doses in the target were calculated.The first one, named Dall, was calculated by tracking the point displacements in the target manifested on the 4DCT images;the second one, named D4D, was calculated based on the point displacements along the whole breathing motion during 4DCT scanning.Dose discrepancy between D4D and Dall was calculated to evaluate the correlation between breathing pattern and dose discrepancy in the target.Results The dose discrepancy in the target was correlated with mean motion excursion and the standard deviation of motion excursion.ΔDmin(ΔD99) in the target increased from 2.39%(2.04%) to 11.91%(5.24%) as the mean motion excursion increased from 5 mm to 15 mm, and increased from 5.93%(2.15%) to 14.65%(5.01%) as the standard deviation of motion excursion increased from 15% to 45% of the mean motion excursion.When the mean period increased from 3 s to 5 s or the standard deviation of period increased from 10% to 40% of the mean period,ΔDmin(ΔD99) in the target was greater than 6.0%(2.0%), but less than 9.0%(3.0%).When the target diameter was 2 cm, 3 cm, and 4 cm,ΔDminΔD99) in the target was 11.88%(5.50%), 6.91%(2.42%), and 7.53%(3.62%), respectively.Conclusions There is a large discrepancy between the cumulative doses calculated using 4DCT images and 4DCT scans (for real-time respiratory motions) when the patient has irregular breathing.This dose discrepancy depends on mean motion excursion and the standard deviation of motion excursion, but has little relationship with mean period, the standard deviation of period, and tumor volume.
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Objective To measure the actual absorbed dose of the target in the QUASAR Respiratory Motion Phantom using the CyberKnife Synchrony Respiratory Tracking System, and to evaluate the effect of density heterogeneity on the absorbed dose of tumor gross target volume ( GTV ) . Methods Nine groups were obtained by making different patterns of QUASAR phantom:rib thickness of 0, 20, and 50 mm, and motion amplitudes of 0, 10, and 15 mm. The nine groups were treated with static computed tomography (CT) in different time phases of four-dimensional CT (4DCT) plan, with the same beam and number of monitor units, and the 4D accumulated dose was calculated. The doses of static and 4D plans were calculated using Ray-tracing and Monte Carlo algorithms, and the absorbed doses of GTV in the nine groups were measured at the same time. Results There were a decrease in calculated absorbed dose of GTV and an increase in deviation between the planned and actual dose, with the increases in simulated rib thickness and motion amplitude. Conclusions The density heterogeneity has an impact on the absorbed dose of GTV. Both static CT and 4DCT plan can evaluate the absorbed dose of GTV in case of small rib thickness and motion amplitude, and 4DCT plan with Monte Carlo algorithm may be the optimal method for evaluation of the absorbed dose of GTV in case of large rib thickness and motion amplitude ( deviation<3%)
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Objective To measure the actual absorbed dose of the target in the QUASAR Respiratory Motion Phantom using the CyberKnife Synchrony Respiratory Tracking System, and to evaluate the effect of density heterogeneity on the absorbed dose of tumor gross target volume ( GTV ) . Methods Nine groups were obtained by making different patterns of QUASAR phantom:rib thickness of 0, 20, and 50 mm, and motion amplitudes of 0, 10, and 15 mm. The nine groups were treated with static computed tomography (CT) in different time phases of four-dimensional CT (4DCT) plan, with the same beam and number of monitor units, and the 4D accumulated dose was calculated. The doses of static and 4D plans were calculated using Ray-tracing and Monte Carlo algorithms, and the absorbed doses of GTV in the nine groups were measured at the same time. Results There were a decrease in calculated absorbed dose of GTV and an increase in deviation between the planned and actual dose, with the increases in simulated rib thickness and motion amplitude. Conclusions The density heterogeneity has an impact on the absorbed dose of GTV. Both static CT and 4DCT plan can evaluate the absorbed dose of GTV in case of small rib thickness and motion amplitude, and 4DCT plan with Monte Carlo algorithm may be the optimal method for evaluation of the absorbed dose of GTV in case of large rib thickness and motion amplitude ( deviation<3%)
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Objective To evaluate the repeatability of the aperture sizes based on the Iris variable aperture collimator (Iris collimator) of CvberKnife VSITM.Methods Radiochromic films were placed at 800 mm of source-to-axis distance (SAD),and Iris quality assurance (QA) software was used to extract the information from the digital images,which were exposured by X-ray beams.Results The average aperture accuracy of Iris collimator was better than 0.11 mm over the beam range 5-40 mm,and the accuracy for 50 mm and 60 mm beams was within 0.19 mm.Conclusions The results suggest a good repeatability of aperture sizes for the CyberKnife VSITM Iris collimator.
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Objective To explore the relationship between DLG value and planning dose distribution and actual treatment dose distribution.Methods IMRT and VMAT plans were generated in Eclipse TPS for a typical whole pelvis case,separately.For IMRT plan,MLC position and actual fluence were calculated for each DLG value with the same optimal fluence.Plans with different DLGs of 0 cm and 0.3 cm were compared by several dosimetric indexes.For exploring the PTV mean dose difference between planning dose and actual IMRT or VMAT treatment,planning dose was recalculated with fixed MLC position and different DLGs.Results Dosimetric differences of PTV V50,rectum V40,bladder V40,small bowel V35,left and right femoral head Dmax were 1.49％,0.72％,0.82％,0.68％,0.02 and 0.14 Gy respectively,the average leaf pair width of MLC segments was correlated with DLG (R2 =0.996,P ＜0.05) and reduced with the increase of DLG.In actual treatment,3.95％ and 1.5％ mean dose reduction in PTV were observed while DLG increased per 0.1 cm in the typical pelvis case,in IMRT and VMAT treatment respectively.Conclusions DLG can result in the change of MLC position and the dose difference between planning and actual treatment.
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Objective To investigate the set-up error of CR in total body irradiation localization and lung shielding.Methods TOR 18FG software was employed to measure the image quality of images at kV and MV levels.The clinical processes were established and the positioning error was analyzed.Results The low contrast resolution and spatial resolution of MV level images were much worse than those at kV level in the condition of total body irradiation,but the image at MV level could be used to identify the high contrast tissues and employed in total body irradiation.The longitudinal errors were (0.50 ± 1.65) cm for left lung and (1.16 ± 1.56)cm for right lung in A P direction,while (1.12 ± 2.22)cm and (0.41 ± 2.16)cm respectively in PA direction.The errors of lateral were (0.81 ± 1.19)cm for left lung and (0.43 ±1.20)cm for right lung in AP direction,while (0.31 ± 1.64)cm and (0.55 ± 1.49)cm respectively in PA direction.Conclusions Application of CR in total body irradiation could make positioning in treatment much easily and reduce the localization errors.
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Objective To explore the dose rate response characterization of four kinds of dosimeters for clinical application.Methods Within the range of 100-600 cGy/min,the dose rate responses of the PTW 0.6 cm3 ion chamber,0.015 cm3 ion chamber,Matrixx Evolution 2D diode array and MapCHECK 2D diode array under the same measuring conditions were measured.The dose rate response of the PTW 0.6 cm3 ion chamber under different energy and working voltage were analyzed.Results All ionization chambe.r types of measured equipment showed certain dose rate dependence for 6 MV X-rays.All the differences were below 1％.The dose rate dependence disappeared for 15 MV X-rays.The 2D diode array had strong dose rate dependence and the response difference was about 2％.Conclusions It is necessary to test and analyze the dose rate response of the measured equipment in treatment technology with dose rate varying,in order to ensure the precision of daily calibration and dose verification.
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ObjectiveTo explore the effects of different flushing and scanning processing on optical density (A) responding and set up the clinic quality assurance protocol based on silver halide emulsions radiographic films.MethodsSetting different flushing temperature and choosing different batch's film and developer and fixer or fixer in the same batch with different analyzing dose were performed to analyze the effect on A value; The effect of light uniform,the stabilize work time and the noise of different scanning resolution were discussed.ResultsThe A value at the same dose level would enhance as the temperature increased;the responding curve of dose and A value with different batches of films varied a lot;the responding curve of dose and A value with different batches of films and developer and fixer solution had marked variations;the responding of dose and A with the same batches would show some low.The heterogeneity of the scanner would achieve 0.03 ; the A value of the same dose would gradually steady while the time ofscanning was more than 10 minutes:the affect of noise would increase as the dose and resolution ratio increased.ConclusionsThe best processing temperature is 29-31 ℃.Different batches of film couldn't be confounded.A new calibration must be obtained when the film dosimetry to evaluate dose distribution is used.A 5 - 10 min warm up for stabilize work and the best setting resolution/depth lever are 72 dpi/16 bit for scanning films are determined.
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In order to explore a dose distribution verification procedure of intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) and establish its evaluation criteria, we performed 35 two-dimensional (2D) patient-specific IMRT verifications over the year 2006. The percent of pixels passing gamma and the normalized agreement test (NAT) index were mainly used to represent the agreement between the measured and computed dose distributions with three criteria (2%/2 mm, 3%/3 mm and 5%/3 mm) as recommended in the literature. The results were that all cases passed through verifications with three criteria except that the NAT index of one case was beyond the limitation, and the three tolerance levels of 2%/2 mm, 3%/3 mm and 5%/3 mm produced similar clinical verification results but led to different percent of pixels passing gamma and NAT index. Our data showed that the percent of pixels passing gamma and the NAT index were complementary to evaluate future IMRT verifications as two significant metrics. Due to the influence of the noise and the trait of the software, we considered an IMRT plan as acceptable in case of the percent of pixels passing gamma >95% and the NAT index <5 with the 5%/3 mm criteria for IMRT patient-specific quality assurance (QA).