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Objective:To establish a prediction model using the random forest (RF) and support vector machine (SVM) algorithms to achieve the numerical and classification predictions of the gamma passing rate (GPR) for volumetric arc intensity modulation (VMAT) validation.Methods:A total of 258 patients who received VMAT radiotherapy in the 1 st Affiliated Hospital of Wenzhou Medical University from April 2019 to August 2020 were retrospectively selected for patient-specific QA measurements, including 38 patients who received VMAT radiotherapy for head and neck, and 220 patients who received VMAT radiotherapy for chest and abdomen. Thirteen complexity parameters were extracted from the patient′s VMAT plans and the GPRs for VMAT validation under the analysis criteria of 3%/3 mm and 2%/2 mm were collected. The patients were randomly divided into a training cohort (70%) and a validation cohort (30%) , and the complexity parameters for the numerical and classification predictions were screened using the RF and minimum redundancy maximum correlation (mRMR) method, respectively. Complexity models and mixed models were established using PTV volume, subfield width, and smoothness factors based on the RF and SVM algorithms individually. The prediction performance of the established models was analyzed and compared. Results:For the validation cohort, the GPR numerical prediction errors of the complexity models based on RF and SVM under the two analysis criteria are as follows. The root-mean-square errors (RMSEs) under the analysis criterion of 3%/3 mm were 1.788% and 1.753%, respectively; the RMSEs under the analysis criterion of 2%/2 mm were 5.895% and 5.444%, respectively; the mean absolute errors (MAEs) under the analysis criterion of 3%/3 mm were 1.415% and 1.334%, respectively, and the MAEs under the analysis criteria of 2%/2 mm were 4.644% and 4.255%, respectively. For the validation cohort, the GPR numerical prediction errors of the mixed models based on RF and SVM under the two analysis criteria were as follows. The RMSEs under the analysis criterion of 3%/3 mm were 1.760% and 1.815%, respectively; the RMSEs under the analysis criterion of 2%/2 mm were 5.693% and 5.590%, respectively; the MAEs under the analysis criterion of 3%/3 mm were 1.386% and 1.319%, respectively, and the MAEs under the analysis criteria of 2%/2 mm were 4.523% and 4.310, respectively. For the validation cohort, the AUC result of the GPR classification prediction of the complexity models based on RF and SVM were 0.790 and 0.793, respectively under the analysis criterion of 3%/3 mm and were 0.763 and 0.754, respectively under the analysis criterion of 2%/2 mm. For the validation cohort, the AUC result of the GPR classification prediction of the mixed models based on RF and SVM were 0.806 and 0.859, respectively under the analysis criterion of 3%/3 mm and were 0.796 and 0.796, respectively under the analysis criterion of 2%/2 mm cohort.Conclusions:Complexity models and mixed models were developed based on the RF and SVM method. Both types of models allow for the numerical and classification predictions of the GPRs of VMAT radiotherapy plans under analysis criteria of 3%/3 mm and 2%/2 mm. The mixed models have higher prediction accuracy than the complexity models.
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Abstract Background: Whole-brain radiation therapy (WBRT) and stereotactic radiosurgery (SRS) are two treatment modalities commonly utilized to treat brain metastases (BMs). Aim: The purpose of this study is to analyse retrospectively the local control and survival of patients with BMs of breast cancer (BC) treated via radiosurgery using Volumetric Modulated Arc Therapy (VMAT-RS). Methods: 18 patients with 41 BMs of BC and treated by VMAT-RS were studied. They were classified according to the molecular subtype of BC and the modified breast graded prognostic assessment -GPA- index. Patients presented 1-4 BMs, which were treated with 5 non-coplanar VMAT arcs. The spatial distribution of BMs, the influence of receptor status on the location of the lesions and survival assessed via the Kaplan-Meier model were analyzed. Results: The median survival time (MST) was 19.7 months. Statistically significant differences were determined in the MST according to the Karnofsky performance status (p= 0.02) and the HER2 status (p= 0.004), being more prolonged in the HER2+ patients. Finally, our results showed that the cerebellum is the predominant site of breast cancer BMs, and also suggested that HER2+BMs had a predilection for some structures of the posterior circulation, such as the cerebellum, brainstem and occipital lobes (p= 0.048). Conclusions: The VMAT-RS is a technique with an overall survival comparable to other radiosurgery techniques. The baseline situation at the time of treatment, the modified breast-GPA and the molecular subtypes, are factors that significantly influence patient survival.
Resumen Antecedentes: La radioterapia holocraneal (WBRT) y la radiocirugía estereotáctica (SRS) son dos modalidades de tratamiento comúnmente empleados para el tratamiento de las metástasis cerebrales (BMs). Objetivo: El propósito de este estudio es analizar de forma retrospectiva el control local y la supervivencia de los pacientes con BMs de cáncer de mama (BC) tratados mediante radiocirugía empleando arcoterapia volumétrica modulada (VMAT-RS). Métodos: Se analizaron 18 pacientes con 41 BMs de BC tratados mediante VMAT-RS. Se clasificaron según el subtipo molecular de BC y el GPA (Graded Prognostic Assessment) modificado de cáncer de mama. Los pacientes presentaron de 1-4 BMs, las cuales fueron tratadas con 5 arcos VMAT no coplanares. Se analizó la distribución espacial de las BMs, la influencia del status del receptor en la localización de las lesiones y la supervivencia evaluada mediante el modelo de Kaplan-Meier. Resultados: La mediana del tiempo de supervivencia (MST) fue de 19.7 meses. Se hallaron diferencias estadísticamente significativas en el MST según el índice de Karnofsky (p= 0.02) y el status de HER2 (p= 0.004), siendo más prolongado en las pacientes HER2+. Por último, nuestros resultados mostraron que el cerebelo es el lugar predominante de las BMs de cáncer de mama, y también sugirieron que las BMs HER2+ presentaban una predilección por algunas estructuras de la circulación posterior, como el cerebelo, el tronco cerebral y los lóbulos occipitales (p= 0.048). Conclusiones: VMAT-RS es una técnica con una supervivencia global comparable a otras técnicas de radiocirugía. La situación basal en el momento del tratamiento, el GPA modificado de cáncer de mama así como los subtipos moleculares de cáncer de mama, son factores que influyen de forma significativa en la supervivencia de los pacientes.
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Objective To compare the dosimetric differences in volumetric modulated arc therapy (VMAT) of Monaco planning system for nasopharyngeal carcinoma between Pareto and Constrained optimization in order to provide a reference for future mode selection. Methods Select 20 patients with nasopharyngeal carcinoma whom were calculated by Pareto and Constrained modes in the same CT image. Prescription dose of target PGTV, PTV1 and PTV2 was 70.29、60.39 and 54.45 Gy with 33 fractions, 5 times a week. The differences in target dose, organs at-risk dose, monitor units and segments were compared in the condition of 95% of the target volume reached the prescribed dose. Results Compared with Pareto group, Constrained group achieved a better HI and CI. CI of PGTV and PTV1 signed statistical differences (P < 0.05). Dose of OARs in Constrained group were all lower than those in Pareto group except Optical-l and lens-l. The differences of spinal cord prv dose and V30 of Parotid-r between two groups was significant (P < 0.05) while the differences of monitor units and segments between two groups was not significant (P > 0.05). Conclusion The length of middle turbinate is negatively correlated with the occurrence and severity of CMS. There is no significant correlation between the degree of curling and the occurrence of CMS, but patients with lower degree of curling of middle turbinate may have more serious CMS.
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Objective To study the dosimetry effect of Dw and Dm middle and lower esophageal cancer in Monaco treatment planning system (TPS). Methods 30 patients with T3N0M0StageⅡa middle and lower esophageal cancer were selected for experiment. For each patient, optimize the plan using dose to water (Dw) and dose to medium (Dm) dose calculation mode, then rescale prescription dose to 95% volume of PTV. Compare the difference in the two mode, conformity index (CI), Homogeneity index (HI), Mean dose (Dmean), Minimum dose (Dmin), Maximum dose (D2), Dose to Organ at risk (OAR), MU, Optimization time, photon usage, and QA results of MatriXX and Arc Check. Use SPSS for multivariate analysis. Results In the dose evaluation of the middle and lower esophageal cancer cases under different dose calculation methods, the spinal cord, trachea, V20 of the whole lung, and D2 of the liver have significant dosimetric differences, the dose value, the sequential dose results were compared as (37.92 ± 1.11)/(35.85 ± 1.08), (59.91 ± 1.43)/(60.25 ± 0.98), (22.52 ± 1.75)/(21.38 ± 2.01), (42.89 ± 0.52)/(41.73 ± 0.58). In the comparison of dose cloud distribution, the difference is mainly located in the cavity and the inner wall of the lung in the target area, the dose in the target cavity in the Dw group is higher than that in the Dm group. The dose in the inner and outer walls of the lung cavity in the Dw group are slightly adducted than that in the Dm group, especially in the central area.Dose QA of MartiXX (3%-3 mm) and Arc Check (2%-2 mm) with different dose calculation methods of 60 plans of 30 cases have all passed clinical requirements. Dm Group is better than Dw group. Conclusion It is recommended to use Dm dose calculation method for Monaco 5.11 TPS in the condition of treatment planning for middle and lower esophageal cancer.
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Objective To explore the dosimetric differences of radiotherapy plan for cervical cancer with 4 different fluence smoothing (FS) parameters using Monaco treatment planning system (Monaco TPS). Methods Fifteen patients with ⅠB2 stage cervical cancer in our hospital were enrolled in this study. And a 2 Volumetric Modulated Arc Therapy (VMAT) plan for each patient were completed by Monaco 5.11 TPS according to the X-Ray Voxel Monte Carlo (XVMC) method. For each plan was optimized by FS function, with the level of Off, Low, Medium and High. To compare the difference of plan optimization time, conformity index (CI), Homogeneity index (HI), Dmean, Dmin, D2% of PTV，dose to the organ at risk (OAR)，the number of Segments# and MU#，estimated total delivery time (ETDT), quantum Efficiency (QE) of the plans, the formation of Segments# with the same angle and verification of inserting 729 two-dimensional matrix into PTW octavius 4D module of different FS function levels, with the precondition of the Prescription isodose curve covering 95% of the target area. The data was analysed by multivariate factor analysis with the application of SPSS, and P < 0.05 was considered as statistically significant. And the Planned revenue score of different FS levels was also calculated. Results Except for the Dmin of PTV (the lowest value is (32.09 ± 0.26) Gy for the Off group, and the highest value is (35.98 ± 0.42) Gy for the High group), V40 of the rectum (the lowest value in the Medium group is 55.88% ± 2.02%, and the highest value in the High group was 61.90% ± 2.98%) and bladder (the lowest value was 45.01% ± 2.08% in the Medium group, and the highest value is 50.45% ± 1.98% in the High group), the V20 (the lowest value High group was 49.05% ± 1.98%, the highest value Off group was 56.52% ± 1.75%) of femoral head (P < 0.05), there was no significant difference of the dose assessment results for PTV and OARs in 4 different FS function levels. In the High level, the ETDT, QE and MU# were showed better than other groups evidently, however, the number of Segments# showed no significant difference. The plan validation results was increased with the improvement of FS function level, and the level of High was considered to be the optimal. To compare the score of overall benefits of the plan, the level of Medium (−17.18 ± 0.05) got the highest score, and the Low group (−17.58 ± 0.05) and the High group (−17.42 ± 0.06) have similar scores, and Off group (−18.81 ± 0.08) has the lowest score. Conclusion Different FS levels of the Monaco 5.11 TPS can optimize the radiotherapy plan for cervical cancer, but the level of Medium is considered to be the most applicable.
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Objective This study aims to compare the advantages and disadvantages of the three techniques in improving the target volume dose and protecting the auris media cavity and eustachian tube isthmus region by investigating the dosimetric differences of three whole-brain radiotherapy techniques. Methods Thirty patients with whole brain metastases were randomly selected to design fixed field intensity modulated radiotherapy (ff-IMRT) plan, volumetric arc modulated therapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) plan, and to meet a 95% PTV prescription dose (40 Gy). The dosimetric parameters and monitor units of the target volume and organ at risk (OAR) in the three groups of treatment plans were compared and analyzed. Results The Conformity Index (CI) of the ff-IMRT plan (0.93 ± 0.02) was better than the VMAT plan (0.89 ± 0.01) and the 3DCRT plan (0.73 ± 0.03), respectively, and the difference was statistically significant (P < 0.05). The Homogeneity Index (HI) of the three plans were ff-IMRT (0.05 ± 0.01)、VMAT(0.08 ± 0.1) and 3DCRT (0.08 ± 0.01), respectively, and the difference was not statistically significant (P > 0.05). The Gradient Index (GI) were ff-IMRT (1.77 ± 0.1), VMAT (1.61 ± 0.07), 3DCRT (1.39 ± 0.08), respectively. The difference was statistically significant (P < 0.05). The monitor units (MU) were ff-IMRT (1551.97 ± 85.02), VMAT (303.7 ± 24.28) and 3DCRT (226.2 ± 2.5), respectively, the difference was statistically significant (P < 0.05). The Dmax of the middle ear of the three plans were ff-IMRT (2557.54 ± 477.39) cGy, VMAT (3107.9 ± 362.28) cGy, 3DCRT (4055.37 ± 71.45) cGy, respectively. The Dmax of the eustachian tube isthmus were ff-IMRT (2425 ± 380.4) cGy, VMAT (2902.4 ± 526.3) cGy and 3DCRT (3862.7 ± 135.9) cGy, the difference were statistically significant (P < 0.05). Conclusion In whole-brain radiotherapy, ff-IMRT and VMAT significantly reduced the dose of the bilateral middle ear cavities and eustachian tube isthmus compared with 3DCRT. VMAT is recommended for WBRT for reducing the number of monitor units significantly.
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0bjective To study the angular dependence of optically stimulated luminescent dosimeter (OSLD) with solid phantoms under SSDL radiation level 60Co radiation field, and to discuss the possibility of OSLD in volumetric modulated arc therapy (VMAT) and other rotating irradiation dose audit. Methods OSLDs were embedded in the two phantoms with the same size and material, respectively. The phantom 1 was set to make the first OSLD perpendicular to the beam, and the phantom 2 was set to make the second OSLD parallel to the beam. The OSLDs were irradiated at 8 angles: 0°, 45°, 90°, 135°, 180°, −45°, −90, −135°. The counts of the OSLSs were read and the response of each angle which normalized to 0° were calculated. Results When the OSLDs are perpendicular to the beam, the angular response is between −6.76% ～ +1.5%, with the maximum angular dependence at 90° and −90°. When the OSLDs are parallel to the beam, the angular response is between −1.74%～+1.67%, below 2%. Conclusion It is better to correct the sensitivity of dosimeters by Element Correction Factors (ECF) for dose audit. Under the condition of rotating irradiation, OSLD shoud be set parallel to the beam, which can better reduce the influence of angular dependence and facilitate further application research of VMAT dose audit.
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Objective To compare the irradiated dose to unprotected lymph node stations (LNS) between volume-modulated arc therapy (VMAT) and 5-field intensity-modulated radiotherapy (5F-IMRT) in the treatment of patients with upper thoracic esophageal cancer.Methods A total of 20 patients were selected for re-planning.LNS were not included in the GTV and CTV,instead,LNS were contoured as normal tissues.However,LNS were not constrained in the VMAT and 5F-IMRT inverse optimization for protection.Dosimetric parameters of conformal index (CI),homogeneity index (HI) of targets,V95,V110 of planning target volume (PTV),D V5,V20,V30 of lung,D V25 of heart,Dmax of spinal cord,MU,as well as the equivalent uniform dose (EUD) and V40 of LNS were compared between the two plans.Results 5F-IMRT was superior in PTV_ V95％ (t=-9.4,P＜0.05),but worse in terms of CI (t=-5.3,P＜0.05) compared with VMAT.5F-IMRT reduced the V5 of lung by 10.9％ (t=-7.8,P＜0.05) and the Dmax of spinal cord by 9％ (t=-10.2,P＜0.05),but increased the MU (t=-6.2,P＜0.05) compared with VMAT.The average EUD and V40 of LNS in upper thoracic were significantly increased by 4.7％ and 2.4％ in 5F-IMRT compared with VMAT,respectively.The irradiated doses to LNS were significantly associated with the volume of PTV (R =0.716-0.933,P＜0.05) expect for 106tbL.Conclusions The irradiated doses to unprotected LNS were less for IMRT plans and were highly associated with PTV volume in patients with upper thoracic esophageal cancer.
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Objective To compare the dosimetric differences of volumetric modulated arc therapy (VMAT) plans optimized with 3 different fluence smoothing parameters using Monaco treatment planning system.Methods A total of 15 patients with middle and upper esophageal carcinoma were planned with Low fluence smoothing (Low),Medium fluence smoothing (Medium) and High fluence smoothing (High) during VMAT optimization.The dosimetric differences in D95,D conformity index (CI),homogeneity index (HI) of targets,dose volume histogram (DVH) of organs at risk (OARs),and monitor unit (MU) were compared.Results There were no significant differences in D95,D CI and HI of targets,as well as in V40 and D of the heart,V10,V20 and D of the lung,and segment number among plans optimized with different fluence smoothing techniques (P＞0.05).Plans with high fluence smoothing achieved less V30 of heart,Dmax of cord PRV (t=-2.167,-0.999,P＜0.05),lower MU (t=-3.148,-6.692,P＜O.05),but increased V5 of both lungs (t=1.306,-2.027,P＜O.05)compared with plans with Medium and Low fluence smoothing.Plans with low fluence smoothing irradiated higher dose to the V30 and D to heart (t=O.411,0.589,0.013,P＜0.05),but less V5 of the lungs (t=O.423,P＜0.05) compared with plans with medium fluence smoothing.Conclusions All VMAT plans with 3 different fluence smoothing can meet the clinical requirements.VMAT plans optimized with high fluence smoothing are recommended in the treatment of patients middle and upper thoracic esophageal carcinoma.
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Objective To study the dosimetric characteristics and plan quality of PTV-based intensity modulated proton radiotherapy (IMPT) and volumetric-modulated arc therapy (VMAT) plans for prostate cancer,so as to provide a reference for clinical application.Methods A total of 10 prostate cancer cases were included in this retrospective study.IMPT and RapidArc plans were designed by RayStation and Eclipse TPS based on PTV,respectively.For each case,IMPT plans were generated using multiple field optimization (MFO) technique with two parallel-opposed lateral fields,whereas RapidArc plans were generated using double-arc technique (two full arcs).Final dose calculation of IMPT was conducted by pencil beam (PB) and Monte Carlo (MC) algorithm,respectively,with adopted data model from the pencil beam scanning (PBS) proton therapy system of IBA Protues Plus (IBA Group,Belgium);The data model originated from the linear accelerator of Varian Clinac iX (Varian Medical Systems,America) was used for RapidArc plans.Dosimetric parameters of DVH and dose distribution were used to compare the dose differences in targets and organs at risk (OARs) between these two treatment techniques.Results For targets,HIs of PB-IMPT and MC-IMPT were slightly better than that of RapidArc,but CI of IMPT was slightly lower than that of RapidArc;D1 of PB-IMPT was significantly better than those of MC-IMPT and RapidArc (Z =-2.805,-2.803,P ＜ 0.05).PB-IMPT and MC-IMPT achieved better protection than RapidArc on rectum V30 (Z =-2.191,-1.988,P＜ 0.05) and D (Z =-2.599,-2.497,P＜0.05),bladder V30 (Z=-2.701,-2.701,P＜0.05),V40 (Z=-2.395,-2.395,P＜0.05) and D (Z =-2.701,-2.701,P ＜ 0.05).There was no significant difference between PB-IMPT and MC-IMPT plans for prostate cancer,except for the D1％ [(73.86t67.34) Gy vs.(75.45±2.01) Gy] (RBE) and HI [(0.040±0.010) vs.(0.058±0.020)] of the target.Conclusions Both techniques can meet the clinical requirements,but IMPT showed significant dosimetric advantages compared with RapidArch by reducing the dose to OARs and improving the plan quality.
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Objective@#To compare the irradiated dose to unprotected lymph node stations (LNS) between volume-modulated arc therapy (VMAT) and 5-field intensity-modulated radiotherapy (5F-IMRT) in the treatment of patients with upper thoracic esophageal cancer.@*Methods@#A total of 20 patients were selected for re-planning. LNS were not included in the GTV and CTV, instead, LNS were contoured as normal tissues. However, LNS were not constrained in the VMAT and 5F-IMRT inverse optimization for protection. Dosimetric parameters of conformal index (CI), homogeneity index (HI) of targets, V95, V110 of planning target volume (PTV), Dmean, V5, V20, V30 of lung, Dmean, V25 of heart, Dmax of spinal cord, MU, as well as the equivalent uniform dose (EUD) and V40 of LNS were compared between the two plans.@*Results@#5F-IMRT was superior in PTV_V95% (t=-9.4, P<0.05), but worse in terms of CI (t=-5.3, P<0.05) compared with VMAT. 5F-IMRT reduced the V5 of lung by 10.9% (t=-7.8, P<0.05) and the Dmax of spinal cord by 9% (t=-10.2, P<0.05), but increased the MU (t=-6.2, P<0.05) compared with VMAT. The average EUD and V40 of LNS in upper thoracic were significantly increased by 4.7% and 2.4% in 5F-IMRT compared with VMAT, respectively. The irradiated doses to LNS were significantly associated with the volume of PTV (R=0.716-0.933, P<0.05) expect for 106tbL.@*Conclusions@#The irradiated doses to unprotected LNS were less for IMRT plans and were highly associated with PTV volume in patients with upper thoracic esophageal cancer.
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Objective@#To compare the dosimetric differences of volumetric modulated arc therapy (VMAT) plans optimized with 3 different fluence smoothing parameters using Monaco treatment planning system.@*Methods@#A total of 15 patients with middle and upper esophageal carcinoma were planned with Low fluence smoothing (Low), Medium fluence smoothing (Medium) and High fluence smoothing(High) during VMAT optimization. The dosimetric differences in D95, Dmean, conformity index (CI), homogeneity index (HI) of targets, dose volume histogram (DVH) of organs at risk (OARs), and monitor unit (MU) were compared.@*Results@#There were no significant differences in D95, Dmean, CI and HI of targets, as well as in V40 and Dmean of the heart, V10, V20 and Dmean of the lung , and segment number among plans optimized with different fluence smoothing techniques (P>0.05). Plans with high fluence smoothing achieved less V30 of heart, Dmax of cord PRV(t=-2.167, -0.999, P<0.05), lower MU (t=-3.148, -6.692, P<0.05), but increased V5 of both lungs (t=1.306, -2.027, P<0.05) compared with plans with Medium and Low fluence smoothing. Plans with low fluence smoothing irradiated higher dose to the V30 and Dmean to heart (t=0.411, 0.589, 0.013, P<0.05), but less V5 of the lungs (t=0.423, P<0.05) compared with plans with medium fluence smoothing.@*Conclusions@#All VMAT plans with 3 different fluence smoothing can meet the clinical requirements. VMAT plans optimized with high fluence smoothing are recommended in the treatment of patients middle and upper thoracic esophageal carcinoma.
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Objective@#To study the dosimetric characteristics and plan quality of PTV-based intensity modulated proton radiotherapy (IMPT) and volumetric-modulated arc therapy (VMAT) plans for prostate cancer, so as to provide a reference for clinical application.@*Methods@#A total of 10 prostate cancer cases were included in this retrospective study. IMPT and RapidArc plans were designed by RayStation and Eclipse TPS based on PTV, respectively. For each case, IMPT plans were generated using multiple field optimization (MFO) technique with two parallel-opposed lateral fields, whereas RapidArc plans were generated using double-arc technique (two full arcs). Final dose calculation of IMPT was conducted by pencil beam(PB) and Monte Carlo (MC) algorithm, respectively, with adopted data model from the pencil beam scanning (PBS) proton therapy system of IBA Protues Plus(IBA Group, Belgium); The data model originated from the linear accelerator of Varian Clinac iX (Varian Medical Systems, America) was used for RapidArc plans. Dosimetric parameters of DVH and dose distribution were used to compare the dose differences in targets and organs at risk (OARs) between these two treatment techniques.@*Results@#For targets, HIs of PB-IMPT and MC-IMPT were slightly better than that of RapidArc , but CI of IMPT was slightly lower than that of RapidArc; D1% of PB-IMPT was significantly better than those of MC-IMPT and RapidArc (Z=-2.805, -2.803, P<0.05). PB-IMPT and MC-IMPT achieved better protection than RapidArc on rectum V30(Z=-2.191, -1.988, P<0.05)and Dmean(Z=-2.599, -2.497, P<0.05), bladder V30(Z=-2.701, -2.701, P<0.05), V40(Z=-2.395, -2.395, P<0.05)and Dmean(Z=-2.701, -2.701, P<0.05). There was no significant difference between PB-IMPT and MC-IMPT plans for prostate cancer, except for the D1% [(73.86±67.34) Gy vs.(75.45±2.01) Gy] (RBE) and HI [(0.040±0.010) vs. (0.058±0.020)] of the target.@*Conclusions@#Both techniques can meet the clinical requirements, but IMPT showed significant dosimetric advantages compared with RapidArch by reducing the dose to OARs and improving the plan quality.
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Objective The aim of this study was to evaluate theβ-cell mass ( BCM) in patients with type 2 diabetes mellitus( T2D) by PET/CT using [ 18 F]-FP-(+)-DTBZ, which is a vesicular monoamine transporter type 2 molecular probe. The feasibility of pancreatic head, body and tail as the target area was investigated for evaluation of the BCM in T2D. Methods 15 subjects ( 8 with T2D, and 7 as control) were involved in this study with 20 min static PET imaging at 40 min post injection of [ 18 F]-FP-(+)-DTBZ. The volume of interest ( VOIs) of pancreatic head, body and tail were drawn and quantitatively assessed. Spleens were collected as reference tissue for SUVR calculation. Results SUVR in the pancreatic head ( SUVR=1.72 ± 0.47) and pancreatic body, tail ( SUVR=1.85 ± 0.41) in T2D group was no significant difference, and no significant difference was observed in the pancreatic head (SUVR=2.54±0.57) and pancreatic body, tail(SUVR=2.73±0.41) in control group as well. In T2D group, a significant decreased SUVR was found in pancreatic head (P=0.0088) and pancreatic body and tail (P=0.0012) compared with controls. Conclusion The VMAT2 molecular probe [ 18 F]-FP-(+)-DTBZ can be used to evaluate BCM in patients with T2D.
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Objective To investigate the impact of adopting different dose grid resolution during volumetric modulated arc therapy (VMAT) planning on COMPASS pass rate.Methods A total of 10 patients with cervical cancer were enrolled.Four types of VMAT plans (plan1,plan2,plan3,plan4) were designed for each patient,with dose grid resolution of 0.2 cm × 0.2 cm × 0.2 cm,0.3 cm × 0.3 cm ×0.3 cm,0.4 cm ×0.4 cm ×0.4 cm and 0.5 cm ×0.5 cm ×0.5 cm,respectively.The plans were exported to Linac and conducted,then measured by COMPASS.The discrepancies were analyzed,which were obtained by comparing reconstructed dose from COMPASS and dose from TPS optimization.Results For tumor volume,the mean value of Dmean and D95 were ＜ 0.5％ and ＜ 1.3％ respectively,and the standard deviation were both ＜ 1.0％.For organs at risk (OAR),the max discrepancies were Dmean of femur with-6.7％,-7.0％,-8.0％,-5.8％,and V35 of rectum with 4.9％,-6.3％,-6.1％,-5.7％ in four types of VMAT plans.The γ (3％,3 am) rate of tumor volume was ＞95％ with standard deviation ＜ 2.5％,with no statistically significant difference among the four types of plans (P ＞0.05).The γ (3％,3 mm) rate of OARs were ＞ 98％ except femur (＞ 95％),and the standard deviations were within 1.9％-6.1％,with no statistical significance (P ＞0.05).The average γ rate of tumor volume and OARs were ＜ 0.4 except femur (＞ 0.4),with no statistically significant difference among four types of VMAT plans (P ＞ 0.05).Conclusions COMPASS pass rate was not influenced by the dose grid resolution between 0.2 ～ 0.5 cm for VMAT plan.
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Objective To compare dosimetric parameters between automated and manualvolumetric modulated arc therapy(VMAT) plans in the treatment of postoperative cervical cancer patients,and to investigatethe feasibility and dosimetric advantage of the automated VMAT planning.Methods Automated and manual VMAT plans were generated with Pinnacle3 treatment planning system (TPS) for twenty-three postoperative cervical cancer patients,including eight patients in stage Ⅱ A and fifteen in stage Ⅱ B,respectively.The differences in D D95,conformity index (CI) and homogeneity index (HI) of target,as well as dose volume histogram (DVH) of organs at risk (OAR),planning time,average optimization time and monitor unit (MU) were compared between automated and manual VMAT plans.Results The average D CI and HI of automated VMAT plans were better than those of manual VMAT plans (t=4.65-14.92,P ＜0.05).There was no significant difference in D95 (P ＞0.05).The automated VMAT plans achieved better average dosimetric parameters on OARs compared with the manual VMAT plans (t =3.30-14.42,P ＜ 0.05).Automated VMAT plans had a significantly shorter planning time (72 min,t =3.85,P ＜ 0.05) and interruption frequency (twice,t =5.41,P ＜ 0.05) than manual VMAT plans.However,automated VMAT plans had a higher average MU than manual VMAT plans with an average MU of 819 ± 53 and 638 ± 41 for automated and manual VMAT plans,respectively.Conclusions It is feasible to generate automated VMAT plans with Pinnacle3 TPS for postoperative cervical cancer patients.The automated VMAT plans increase the plan quality and reduce the optimization time compare with manual VMAT plans.Automated technique also eliminates the influence of human factors on the plan quality.
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Objective To acquire setup error with X-ray volumetric images (XVI) technique during volumetric modulated arc therapy (VMAT) of pelvic tumors in order to provide guidance for the doctor to determine the interval between clinical target volume (CTV) and planning target volume (PTV).~ Totally 20 pelvic tumor patients accepting radiation oncology underwent CBCT scan before the first treatment,and auto registration was executed between CBCT images and planning CT images to determine the setup errors at X,Y and Z directions.Then the patients experienced another CBCT scan to obtain residual setup errors,VMAT was carried out after auto on-line correction by the treatment couch,and the third CBCT scan was performed after the treatment.Totally three times of CBCT scans were implemented every week hereafter.The setup errors were analyzed before and after the treatment,and the target volume margin (MPTV) was calculated accordingly.Results The setup errors at X,Y and Z directions were significantly decreased after correction.The values of MPTV at X,Y and Z directions before correction were 3.89,6.20 and 5.24 mm respectively,and the ones after correction were 1.42,2.42 and 2.40 mm respectively.The decreased values of MPTV were between 2.47 and 3.78 mm,which showed the most significant trend at Y direction.Conclusion VMAT of pelvic tumors based on XVI contributes to decreasing the setup errors and enhancing treatment quality.
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Objective The objective of this study was to compare the differences between Volumetric Modulated Arc Radiotherapy(VMAT)and Fixed Field dynamic Intensity Modulated Radiotherapy(dIMRT)in dose distribution of target and organ at risk and treatment time,and to provide basis for clinical treatment.Methods Ten patients with postoperative of cervical carcinoma were selected,VMAT and seven fields dIMRT plans were designed for each patient in Monaco 5.11 planning system.We compared the differences of dose distribution of target and organ at risk,monitor units and treatment time between VMAT and 7dIMRT.Results The average dose of target for VMAT plan(46.86 Gy)was higher than that of 7dIMRT plan(46.68 Gy)(P<0.05).The percentage of the V10 and V20 of rectum and the V30 of small intestine in VMAT plan was 0.63%,3.34% and 4.14% higher than that in 7dIMRT plan,respectively(P<0.05).The conformal index(CI),homogeneity index(HI)of PTV and the other exposure dose of organ at risk for both plans were no significant differences.The average monitor units and treatment time of VMAT plan were 13.4% and 50.6% than that of 7dIMRT plan,respectively(P<0.05).Conclusion The dose distribution of VMAT plan is better or equal to that of 7dIMRT plan,but the monitor units and treatment time of VMAT plan is decreased significantly,we suggest that VMAT plan should be used for postoperative of cervical carcinoma in clinical.
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Objective To investigate the feasibility and plan quality of the image-guided volumetric modulated arc therapy (VMAT) based voluntary deep exhale breath-holding technique in the stereotactic ablative body radiotherapy (SABR) for liver tumors.Methods Fifteen patients with liver tumors were involved in this study.All patients were immobilized with voluntary deep exhale breath hold (vDEBH) combined with real-time position management (RPM) respiratory gating system.Treatment was planned using VMAT with 2 modified partial arc and re-planned using intensity modulated radiation therapy (IMRT) technique for comparison.Dosimetric parameters were calculated for plan quality assessment.Quality assurance studies included absolute dose and multiple planar dose verifications,total monitor units and delivery time analysis.Daily cone beam computed tomography imaging was used to verify the motions.Results There were no significant dosimetric differences between VMAT and conventional IMRT plans (P ＞0.05).Both techniques were able to minimize doses to organs at risk including normal liver,kidneys,spinal cord,and stomach.However,the average monitor units with VMAT were significantly lower 28.1％ than those with IMRT(t =3.064,P ＜0.05).The average beam-on time in VMAT plans was 31.6％ shorter than that in IMRT plans(t =2.278,P ＜ 0.05).Conclusions The utilization of VMAT in the treatment planning of SABR for liver tumors under breath control mode has better dosimetrics.In comparison to conventional IMRT plans,VMAT plans have higher efficiency and feasibility.
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Objective To investigate the effects of hippocampal?sparing intensity?modulated radiotherapy ( IMRT) on dose distribution of target volume and organs at risk ( OARs) in locally advanced nasopharyngeal carcinoma. Methods A retrospective dosimetric analysis was performed among 11 patients with locally advanced nasopharyngeal carcinoma. The MONACO ? v5. 10 Treatment Planning System was used to design three treatment plans:routine volumetric modulated arc therapy ( VMAT ) , hippocampal?sparing VMAT, and nine fixed?fields IMRT. The D98%, D50%, D2%, Dmean , conformity index ( CI ) , and homogeneity index (HI) of planning target volume (PTV) and PTVnx as well as dose distribution of the hippocampus and OARs were evaluated. Using single factor analysis of variance,two group comparative was LSD or paired t?test. Results For the above three plans,the D2% values of PTVnx were ,7 513,and 7 462 cGy,respectively (P=0. 016);the D98% values of PTV were 5837,5812,and 5914 cGy,respectively (P=0. 029);the average D2% values of PTV were 7 399,7 380,and 7 333 cGy,respectively ( P=0. 047);the HI values of PTV were 0. 239,0. 241,and 0. 220,respectively (P=0. 016);the V10 values of the brain stem were 97. 2%,88. 1%,and 90. 3%,respectively ( P=0. 001);the V20 values of the brain stem were 74. 2%, 62. 3%,and 67. 1%,respectively ( P=0. 032);the V30 values of the brain stem were 50. 9%,35. 8%,and 45. 5%, respectively ( P= 0. 020 );the V40 values of brain stem were 24. 4%, 14. 4%, and 23. 3%, respectively ( P=0. 018);the Dmean values of hippocampus were 1 518,899,and 896 cGy,respectively ( P=0. 000);the D40% values of hippocampus were 1 379,642,and 639 cGy,respectively ( P=0. 000);the V10 values of the hippocampus were 54. 1%,25. 1%,and 3. 8%,respectively ( P=0. 000);the V20 values of the hippocampus were 26. 2%, 12. 6%, and 12. 0%, respectively ( P=0. 001 ) . Conclusions Hippocampal?sparing VMAT and nine fixed?fields IMRT can significantly reduce the dose to the hippocampus without affecting dose distribution of target volume and OARs. VMAT may be superior to IMRT because VMAT can simultaneously reduce the dose to the brain stem.