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Objective:To evaluate the effect of rotational errors (antero-posterior) on dosimetric parameters of positive lymph nodes in the long target volumetric modulated arc therapy (VMAT) plan for advanced cervical cancer and investigate its coping strategies.Methods:Clinical data of patients with cervical cancer complicated with para-aortic or inguinal lymph node metastasis admitted to Affiliated Hospital of North Sichuan Medical College were randomly selected and retrospectively analyzed. The target areas of the lymph nodes at different distances from the center of the plan were outlined according to the requirements. After designing the VMAT plan on the CT images of each case, the rotational errors (antero-posterior) were introduced by changing the parameters of the treatment couch, and the dose distribution was reconstructed by dose calculation with other parameters unchanged. Then, the external boundary of the original lymph node target was added according to d=2πr(α/360) ( r is the distance from the center of the lymph node to the plan center), re-planned, and the changes of dosimetric parameters in the target area of the original lymph node were analyzed after the corresponding rotational errors were introduced. Results:When the distance between the lymph node target area and the plan center was 6 cm with an error of 3°, the distance was 9 cm and 12 cm with an error of 2.5°, the distance was 15 cm with an error of 2°, and the distance was 18 cm with an error of 1.5°, the mean change of D 95% was more than 5%. When the rotational errors were ≤1°, the mean change of D 95% in lymph node target area was less than 5%, and when the lymph node was 18 cm away from the treatment plan center, the mean change was more than 3%, reaching 3.75%. When the rotational errors were 0.5° and the distance from the plan center was 18 cm (0.5°, 18 cm), the dose change of lymph node target was more than 5%, reaching 5.58%. At (1°, 15 cm), the V 100% change reached 8.96%, and at (1°, 18 cm), the V 100% change was 14.5%. The D 95% and V 100% parameters of the original lymph node target were changed by less than 1% after adding the external boundary of the original lymph node target and introducing corresponding rotational errors. Conclusions:In the long target area radiotherapy of cervical cancer, the variation of dosimetric parameters of lymph node target was increased with the increase of rotational errors and with the increase of distance from the plan center. It is recommended to increase the efferent boundary of lymph nodes in different positions to avoid underdose by d=2πr(α/360).
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Objective To analyze the effect of the fixed-jaw technique on dosimetric parameters during dynamic intensity-modulated radiotherapy (DIMRT) planning. Methods Ten patients each with nasopharyngeal carcinoma, postoperative cervical cancer, and right breast cancer after radical surgery were selected for this study; all patients underwent DIMRT in our hospital in 2020. After administration at the prescribed dose, two methods were used to design the radiotherapy plan for each patient: split-field technique (SFT) and fixed-jaw technique (FJT). The two plans were compared for the differences in the dosimetric parameters and plan verification pass rate. Results Compared with SFT, FJT showed significant decreases (P <0.05) in the following parameters for patients with nasopharyngeal carcinoma, postoperative cervical cancer, and right breast cancer after radical surgery: number of radiation fields (down by 41.5%, 47.3%, and 34.9%, respectively, t = 7.954, 24.2, and 4.949, respectively), total number of monitor units (MUs) (down by 5.6%, 5.3%, and 13.5%, respectively, t = 3.211, 2.423, and 5.481, respectively), and actual beam-on time (down by 25.3%, 23.8%, and 13.6%, respectively, t = 5.814, 9.208, and 5.655, respectively). There were significant differences in some of the dosimetric parameters for all three types of cancer patients between the two plans (P <0.05). There were no significant differences in the plan verification pass rate (P >0.05). Conclusion FJT can reduce the total number of MUs and actual beam-on time while meeting the requirements for clinically prescribed doses in DIMRT planning.
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Objective:To compare the effects of parameters, such as planning target volume (PTV), calculation grid size, and dose threshold, on the dosimetric verification result of three dosimetric verification systems ArcCHECK, SRS MapCHECK, and 3DMap for stereotactic body radiation therapy (SBRT).Methods:Based on the dosimetric verification result of the SBRT plans of 50 patients, this study compared the effects of PTV (<25 cm 3 and ≥25 cm 3), calculation grid size (1.0, 1.5, and 2.0 mm), and dose threshold (5%, 10%, and 15%) on the γ passing rates of the three dosimetric verification systems at five criteria, i. e., 3 mm/3%, 3 mm/2%, 3 mm/1%, 2 mm/3%, and 2 mm/2%. Results:The changes in PTV affected 3DMap more significantly. With an increase in PTV, the γ passing rates of 3DMap at the criteria of 3 mm/3%, 3 mm/2%, 2 mm/3%, and 2 mm/2% increased by 2.2%, 2.2%, 4.4%, and 4.7% ( t=-2.76, -2.17, -4.72, -3.86, P<0.05), respectively. The increase in the calculation grid from 1.0 mm to 1.5 mm had greater effect on MapCHECK, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 3 mm/1%, 2 mm/3% and 2 mm/2% decreased by 0.7%, 1.1%, 1.7%, 0.9%, 1.5% ( t=-6.15, -6.23, -5.98, -5.11, -8.34, P<0.05), respectively. The increases in the calculation grid from 1.0 mm to 2.0 mm had greater impact on ArcCHECK, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 3 mm/1%, 2 mm/3%, 2 mm/2% decreased by 1.0%, 1.7%, 2.4%, 1.7%, 2.7% ( t=-4.75, -7.3, -8.63, -7.11, -8.26, P<0.05), respectively. The increase in the dose threshold from 5% to 10% had greater impact on ArcCHECK, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 2 mm/3% and 2 mm/2% decreased by 1.1%, 1.4%, 2.5%, and 3.0% ( t=5.20, 5.68, 8.17, 9.99, P<0.05), respectively. Moreover, the increase in the dose threshold from 5% to 15% had more impact on 3DMap, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 2 mm/3%, and 2 mm/2% decreased by 1.6%, 1.7%, 2.8%, and 3.2% ( t=3.25, 2.98, 4.40, 4.21, P<0.05), respectively. Conclusions:Target volume, calculation grid, and dose threshold are influencing factors in the dosimetric verification of three dosimetric verification systems for SBRT. Therefore, the effects of these parameters should be considered for different verification systems in clinical applications.
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Objective:To investigate the feasibility of applying the ArcherQA three-dimensional (3D) dosimetric verification system in intensity-modulated radiotherapy (IMRT) plans for nasopharyngeal carcinoma (NPC).Methods:A retrospective analysis was conducted for 105 NPC patients′ IMRT plans developed using the Eclipse treatment planning system (TPS). Dose verification was conducted using the ArcherQA system and through portal dosimetry (PD). Moreover, this study compared γ passing rates (criteria: 3 mm/3%, TH = 10%) between ArcherQA and PD and the doses delivered to the target volume ( Dmean, D90%) and organs at risk (OARs) ( Dmean) between ArcherQA and TPS, and analyzed the 3D γ passing rates of each organ at risk calculated by ArcherQA. Results:The average 3D γ passing rate calculated by ArcherQA was (99.04±1.01)%, and the average 2D γ passing rate measured by PD was (99.49±0.78)%, with statistically significant differences ( t=-3.35, P< 0.05). The dosimetric differences to the target volume between ArcherQA and TPS were as follows: the average difference in Dmean to the gross tumor volume (GTV) was (0.57±0.48)%, and the average difference in D90% was (0.65±0.56)%. For the target volume, the average γ passing rate was (97.67±3.43)% for GTV, (97.80±4.35)% for GTVnd-L, (97.82±4.07)% for GTVnd-R, (97.88±2.44)% for CTV1, and (96.64±4.32)% for CTV2. The mean dose difference of each target volume was CTV1 (0.57±0.46)%, GTVnd-L (0.85±0.55)%, GTVnd-R (0.73±0.55)%, and CTV2 (0.88±0.52)%. For OARs, the mean γ passing rate was (99.93±0.22)% for the brainstem, (99.17±2.82)% for the optic chiasm, (100±0)% for the lens, (99.56±1.05)% for the spinal cord, (99.00±2.06)% for the thyroid, and (87.86±10.42)% for the trachea. Statistically significant differences in the average doses to OARs were observed ( t=-14.62 to 4.82, P<0.05), except for those to the left optic nerve, the right hippocampus, and the right parotid gland. Conclusions:Based on the high-performance GPU platform and the Monte Carlo dose algorithm, ArcherQA can provide accurate 3D dose distribution and 3D γ passing rates inside patients according to CT images and provide the dose volume histogram (DVH) of various regions of interest (ROIs). Therefore, the ArcherQA three-dimensional dose verification system can be applied to IMRT plans for NPC. Moreover, it is inducive to improve the treatment efficiency since it does not occupy the accelerator operation time.
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@#<b>Objective</b> To investigate the dosimetric effect of truncated regions in computed tomography (CT) images on the targets and organs at risk in volumetric modulated arc therapy (VMAT) for middle thoracic esophageal cancer. <b>Methods</b> CT images of 15 patients with middle thoracic esophageal cancer were selected. Circle masks were used to make the volume of the truncated region account for 10%, 20%, 30%, and 40% of the arm volume, and the corresponding truncated CT images were obtained. The real CT was denoted as CT0. Two radiotherapy plans were made on CT0. One plan was VMAT_1F with full arcs, and the other one was VMAT_3F with arm avoidance. The plans were transplanted to four truncated CT, respectively, and the dosimetric differences between different plans were compared using Wilcoxon signed-rank test. <b>Results</b> Compared with VMAT_1F in CT0, <i>D</i><sub>mean</sub> and <i>V</i><sub>5</sub> of the lung decreased in VMAT_3F, but <i>D</i><sub>max</sub> of the spinal cord, <i>D</i><sub>mean</sub> of the heart, and <i>V</i><sub>20</sub> of the lung increased. In VMAT_3F, there was no statistically significant difference between the dosimetric parameters in the four truncated CT and those in CT0 (all <i>P</i> > 0.05). In VMAT_1F, except for homogeneity index and <i>D</i><sub>max</sub> of the spinal cord, the dosimetric parameters in four truncated CT were significantly different from those in CT0 (<i>P</i> < 0.05). The dosimetric difference increased with the increase in truncated region-to-volume ratio. <b>Conclusion</b> Complete CT data should be collected in clinical practice, and the radiation field avoiding the truncated regionshould be set if necessary to reduce the influence of the truncated region on dosimetry.
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Objective To explore the optimal radiotherapy method by comparing the dosimetric differences of target and organs at risk of four radiotherapy plans for left sided breast cancerafter breast-conserving surgery. Methods Twenty-three patients with left breast cancer were randomly selected and given PTV 25 fractions, 50 Gy prescription dose.TheHybrid_IMRT, rj_IMRT, VMAT and t_VMAT plans were designed for each patients. Dosimetric differences were compared, including dose volume histograms of target and OARs, target homogeneity indexes (HI), conformal indexes (CI) and the machine MUs. Results Target Dosimetric comparison, HI: t_VMAT plan target has highest HI and had significant difference (P ≤ 0.001); The target CI of VMAT plans were 0.967 ± 0.016, had significant difference compared with the other 3 plans (P < 0.05). The CI of rj_ IMRT were 0.942 ± 0.018 better than that of IMRT and t_VMATs. Dosimetric comparison of OARs, left_lung mean dose (MLD_L): rj_IMRT were （8.76 ± 1.52） Gy which were best of 4 plans, and had statistical significance (P < 0.05). Heart mean dose: rj_IMRT were （4.68 ± 0.87） Gy were better than that of VMAT (P < 0.05). Conclusion All of these four plans could be applied in clinical treatments, while the limitations of treatment equipment, patients’ physical conditions and some other factors should be considered before selecting an appropriate one.
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Objective To compare the dosimetric difference of target and organs-at-risk between intensity-modulated radiotherapy (dIMRT) and volumetric modulated arc therapy (VMAT) for bilateral breast cancer, so as to discuss the clinical feasibility of radiotherapy for bilateral breast cancer. Methods The clinical data of 18 patients receiving radical or modified radical mastectomy for confirmed bilateral breast cancer were enrolled in this study. dIMRT plans and VMAT plans were designed for each patient, and discuss the dosimetric data of two radiotherapy plans. Results Both the two plans satisfied the prescription. In terms of the homogeneity index, VMAT plans (0.09 ± 0.02) were superior to dIMRT plans (0.11 ± 0.01, P < 0.05). In terms of the conformity index,VMAT plans (0.82 ± 0.52) were superior to dIMRT plans (0.71 ± 0.51, P < 0.05). Furthermore, VMAT plans (0.98 ± 0.06) were superior to dIMRT plans (1.24 ± 0.08, P < 0.05) in the dose gradient index. The V10、V20、V30 and Dmean of lungs in VMAT plans (39.07 ± 4.92，22.19 ± 4.36，12.81 ± 4.71，1309.03 ± 135.55) were higher than those in dIMRT plans (30.34 ± 4.26，17.56 ± 4.31，6.77 ± 3.93，1201.39 ± 166.77, P < 0.05).Meanwhile, the V5 of lungs in VMAT plans (63.36 ± 9.02) was higher than that in dIMRT plans (58.01 ± 7.17, P > 0.05). However, the V5、V30 and Dmean of heart in VMAT plans (51.98 ± 3.60，3.78 ± 1.76，885.89 ± 59.84) were lower than those in dIMRT plans (77.16 ± 12.11，5.22 ± 2.85，1036.96 ± 151.46, P < 0.05). The Dmax of spinal cord in VMAT plans (2150.42 ± 136.19) was significantly lower than that in dIMRT plans (3008.23 ± 304.15, P < 0.05). Monitor units in VMAT plans（792.61 ± 62.53）was significantly lower than that in dIMRT plans (3225.33 ± 498.66, P < 0.05). Conclusion Although VMAT has many advantages: achieves better homogeneity index and conformity index of target areas, reduces the irradiation dose of organs-at-risk, especially, the irradiation dose of heart and spinal cord is significantly reduced, however, it increases the irradiation dose of lungs. To reduce the recurrence of grade ≥ 2 radiation pneumonia, dIMRT should be better considered in the application of radiotherapy for bilateral breast cancer.
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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 explore the effects of clinical characteristics and dosimetric factors on the survival and prognosis of patients with locally advanced thoracic esophageal squamous cell carcinoma after concurrent chemoradiotherapy (CCRT).Methods:A total of 158 patients with locally advanced thoracic esophageal squamous cell carcinoma undergoing CCRT in Shandong Cancer Hospital, Anyang Cancer Hospital of Henan Province, Tengzhou Central People′s Hospital of Shandong Province and the First Affiliated Hospital of China Medical University from August 2015 to October 2018 were selected as the research subjects. These patients were divided into standard-dose group (50.0-50.4 Gy, n=59) and high-dose group (>50.4 Gy, n=99) according to the radiotherapy dose. The overall survival (OS) and progression-free survival (PFS) of the two groups after treatment were compared. Kaplan-Meier method was used to calculate survival rate and survival comparison was performed by log-rank test. Cox proportional hazard regression model was used to analyze the adverse prognostic factors. The receiver operating characteristic (ROC) curve was used to analyze the predictive value of lung V 30 for patient prognosis. Results:In 158 patients with locally advanced esophageal squamous cell carcinoma, 19 cases (12.03%) had complete remission after CCRT, 103 cases (65.19%) had partial remission, 27 cases (17.09%) had stable disease, 9 cases (5.70%) had progression disease, and the total effective rate was 77.22%. The median OS of 158 patients was 41 months (95% CI: 25-57 months), and the 1- and 3-year OS rates were 76% and 51%, respectively. The median PFS was 24 months (95% CI: 13-35 months), and the 1- and 3-year PFS rates were 60% and 39%, respectively. The 1- and 3-year OS rates in the standard-dose group were 74% and 56%, and those in the high-dose group were 77% and 49%, with no statistically significant difference ( χ2=0.300, P=0.584). The 1- and 3-year PFS rates in the standard-dose group were 62% and 37%, and those in the high-dose group were 59% and 40%, with no statistically significant difference ( χ2<0.001, P=0.990). Univariate analysis showed that the length of the lesion, N stage, clinical stage, short-term efficacy of CCRT, planning target volume (PTV) D max, gross tumor volume (GTV) D mean, V 5, V 10, V 20, V 30, D mean of the left, right and bilateral lung were all the prognostic factors for OS and PFS (all P<0.05). Multivariate analysis showed that the length of the lesion ( HR=2.226, 95% CI: 1.244-3.985, P=0.007), N stage ( HR=2.819, 95% CI: 1.137-6.991, P=0.025), clinical stage ( HR=1.897, 95% CI: 1.079-3.334, P=0.026), short-term efficacy of CCRT ( HR=1.805, 95% CI: 1.250-2.606, P=0.002), left lung V 10 ( HR=0.811, 95% CI: 0.668-0.986, P=0.035), left lung V 30 ( HR=0.617, 95% CI: 0.408-0.933, P=0.022), right lung V 20 ( HR=2.067, 95% CI: 1.010-4.231, P=0.047), bilateral lung V 10 ( HR=1.299, 95% CI: 1.016-1.662, P=0.037) and bilateral lung V 30 ( HR=2.368, 95% CI: 1.142-4.910, P=0.021) were independent prognostic factors affecting OS. N stage ( HR=2.433, 95% CI: 1.201-4.931, P=0.014), short-term efficacy of CCRT ( HR=2.067, 95% CI: 1.391-3.071, P<0.001) and bilateral lung V 30 ( HR=0.113, 95% CI: 0.018-0.719, P=0.021) were independent prognostic factors affecting PFS. The ROC curve for predicting OS and PFS showed that the optimal cut-off value of bilateral lung V 30 was 9.5%. Conclusion:Compared with the standard-dose group, increasing the dose of radiotherapy fails to improve the long-term survival of patients with locally advanced thoracic squamous cell carcinoma. Lesion length, N stage, clinical stage, short-term efficacy of CCRT, left lung V 10 and V 30, right lung V 20 , bilateral lung V 10 and V 30 are independent prognostic factors for OS in patients with locally advanced thoracic squamous cell carcinoma. N stage, short-term efficacy of CCRT and bilateral lung V 30 are independent prognostic factors for PFS. When bilateral lung V 30≤9.5%, the patients′ OS and PFS will benefit from the treatment.
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Objective:To investigate the implementation procedures and dosimetric verification of the first patient treated with total body irradiation (TBI) based on volumetric modulated arc therapy (VMAT).Methods:Two sets of CT images were acquired under the head-in first and foot-in first to contour the planning target volume (PTV) of the cranial and caudal segments to accomplish the treatment of the whole body length, on which two interrelated plans of 5 subsequent isocenters with a total of 15 VMAT fields were performed to cover all PTVs. The plans were prescribed to ensure 90% PTV dose coverage with a total dose of 12 Gy in 6 fractions. Firstly, a dose optimization was performed on the caudal CT images, then the cranial CT images were optimized based on the dose distribution of the caudal CT images. The evaluation of the final treatment plan was carried out based on a plan sum of both two sets of images. The parameters of PTV and organs at risk (OARs) were measured by dose volume histograms from the accumulated plan. The quality assurance comprised the verification of the VMAT plans for each individual isocenter via Delta4 phantom. The dose distribution in the overlapped region between two adjacent central fields was verified with EBT3 film. The absolute dose at the overlapped region between two images was measured via Pinpoint chamber. In vivo dosimetry on the patient′s skin was monitored by MOSFET dosimeters. The results of planning parameters and treatment duration were analyzed. Results:The mean doses of two segments of PTVs were 12.45 Gy and 12.37 Gy. The mean dose for the lung was 10.8 Gy. The machine unit (MU) and mean treatment delivery time were 2 883 MU and 24.3 min, and the mean total time per fraction was 121 min. The mean 3%/3 mmγ-analysis pass rate for each isocenter VMAT plan was (99.74±0.42)%, and the mean 5%/5 mmγ-analysis pass rate for the overlapped region was (90.11±2.72)%. The average deviation of absolute dose in the overlap region of the caudal and cranial images was (3.6±0.4)%. In vivo measurement of 8 points on the patient showed that the dose of each region was ranged from 1.57 Gy to 2.04 Gy. Conclusion:According to the results of dosimetric verification, TBI based on multi-isocenter VMAT can be applied in clinical practice, which remains to be improved in terms of dose distribution, measurement results and clinical efficiency.
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Background:Palliative radiotherapy offers significant relief in the huge physical distress of patients with bony metastasis. The enormous potential of conformal techniques has not been tested in palliative settings. However,the increasing life span of patients with metastatic disease demands to optimize the radiotherapy techniques to provide maximal durable symptomatic relief. Despitean increase in the utilization of the 3DCRT technique for palliative bony metastasis, the optimal beam arrangement remains unknown. Materials and Methods:Ten patients of vertebral bony metastasis were retrospectively selected and four virtual 3DCRT plans were generated for each patient. The field approaches were a single field, two fields, three fields and five field approaches. For PTV, D90, D50, Dmean, Conformity index (CI) were evaluated.Dmean was evaluated for the esophagus, bowel, kidneys, and combined lungs. Dose-volume histograms were computed for the various treatment plans and compared. Statistical analysis was done by ANOVA test. Results:A total of forty radiotherapy plans were generated. PTV parameters were significantly better with two field plans over one field plans in terms of D90 (p= 0.002), D50 (p= 0.02), Dmean(p=0.0009). Dmeanwassignificantly better with three field approach compared to two field approach (p=0.0006). The Dmeanwas significantly increased for organs at risk in two fields and three field plans.Five field approach did not showan advantage in terms of dosimetry of PTV but there was a significant rise in the dose to Organs at risk (OAR’s). Conclusion:The three field plans showed better dose distribution to the PTV with an acceptable increase in the dose to OAR’s.
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Objective To evaluate the value of two oral mucosal contouring methods for predicting acute radiation-induced oral mucositis (A-ROM) in nasopharyngeal carcinoma (NPC) patients.Methods A total of 150 AJCC 7th stage Ⅱ-ⅣB NPCs receiving radical tomotherapy (TOMO) in Zhejiang Cancer Hospital from 2017 to 2019 were included in this prospective observational study.Oral cavity contour (OCC) and mucosal surface contour (MSC) were applied to delineate the oral mucosal structure.A-ROM grade was prospectively assessed and recorded weekly according to RTOG scoring criteria.The prediction value of two methods for A-ROM was statistically compared.Results The incidence rate of ≥ 3 grade A-ROM was 33.3％.In univariate analysis,V5,V10,V15,V45,V50,V55,V60,V65 and V70 of OCC and V5,V10,V50,V55,V60,V65,V70 and Dmean of MSC were significantly correlated with the risk of ≥3 grade A-ROM (all P＜0.05).In binary logistic regression analysis,gender and smoking were significantly associated with the incidence of ≥3 grade A-ROM by using OCC (male vs.female:OR=0.141,95％CI=0.037-0.538,P=0.004;smoking vs.non-smoking:OR=5.109,95％CI=1.413-18.470,P=0.013).For MSC,gender,smoking,N stage and MSC-V55 were the independent predictors (male vs.female:OR=0.129,95％CI=0.032-0.519,P=0.004;smoking vs.non-smoking:OR=4.448,95％CI=1.224-16.164,P=0.023;N stage:OR=2.291,95％CI=1.268-4.137,P=0.006;MSC-V55:OR=1.432,95％CI=1.008-2.033,P=0.045).The cutoff value of MSC-V55 was 7.70％,the area under ROC curve was 0.754,the sensitivity and specificity were 0.680 and 0.740,retrospectively (all P＜0.001).Conclusions Compared with OCC,MSC yields a higher prediction accuracy for the severity of A-ROM in nasopharyngeal carcinoma patients receiving TOMO treatment.
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Objective@#To evaluate the value of two oral mucosal contouring methods for predicting acute radiation-induced oral mucositis (A-ROM) in nasopharyngeal carcinoma (NPC) patients.@*Methods@#A total of 150 AJCC 7th stage Ⅱ-IVB NPCs receiving radical tomotherapy (TOMO) in Zhejiang Cancer Hospital from 2017 to 2019 were included in this prospective observational study. Oral cavity contour (OCC) and mucosal surface contour (MSC) were applied to delineate the oral mucosal structure. A-ROM grade was prospectively assessed and recorded weekly according to RTOG scoring criteria. The prediction value of two methods for A-ROM was statistically compared.@*Results@#The incidence rate of ≥3 grade A-ROM was 33.3%. In univariate analysis, V5, V10, V15, V45, V50, V55, V60, V65 and V70 of OCC and V5, V10, V50, V55, V60, V65, V70 and Dmean of MSC were significantly correlated with the risk of ≥3 grade A-ROM (all P<0.05). In binary logistic regression analysis, gender and smoking were significantly associated with the incidence of ≥3 grade A-ROM by using OCC (male vs. female: OR=0.141, 95%CI=0.037-0.538, P=0.004; smoking vs.non-smoking: OR=5.109, 95%CI=1.413-18.470, P=0.013). For MSC, gender, smoking, N stage and MSC- V55 were the independent predictors (male vs. female: OR=0.129, 95%CI=0.032-0.519, P=0.004; smoking vs.non-smoking: OR=4.448, 95%CI=1.224-16.164, P=0.023; N stage: OR=2.291, 95%CI=1.268-4.137, P=0.006; MSC-V55: OR=1.432, 95%CI=1.008-2.033, P=0.045). The cutoff value of MSC-V55 was 7.70%, the area under ROC curve was 0.754, the sensitivity and specificity were 0.680 and 0.740, retrospectively (all P<0.001).@*Conclusions@#Compared with OCC, MSC yields a higher prediction accuracy for the severity of A-ROM in nasopharyngeal carcinoma patients receiving TOMO treatment.
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Context: Due to limited resources and/or affordability by majority of the patients, many centers in low- and middle-income countries are still not able to adapt three-dimensional image-based brachytherapy planning in their routine practice. Aim: The aim of the study was to see the feasibility of using computed tomography (CT)-based plan of the first fraction to treat successive fractions of intracavitary brachytherapy based on the estimation of the physical dosimetric differences between successive applications. Materials and Methods: CT image-based brachytherapy plans of 38 patients who received three insertions of intracavitary application with high-dose-rate brachytherapy have been analyzed. Revised plans for the second and third insertions were generated by adapting dwell time and dwell position of the first insertion plan. The dose to point “A” and maximum doses to 2, 1, and 0.1 cc volumes of the rectum and bladder have been used for dosimetric comparison. Results: The statistical differences of mean point “A” doses were observed insignificant except between original and revised plans for the second insertions. The dosimetric differences between consecutive original and revised plans for the bladder and rectum have not shown any significance except minimum dose to 0.1 cc volume of the rectum for the third insertions. Conclusions: Dosimetric deviation for tumor and organs at risk is within acceptable limit while using CT image-based brachytherapy plan of the first fraction for treating successive fractions
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Introduction and Objective: Anatomic and volumetric changes occur in head-and-neck cancer during fractionated radiotherapy (RT), and the actual dose received by patient is considerably different from the original plan. The purpose of this study is to evaluate volumetric and dosimetric changes occurring during radiation therapy. Patients and Methods: Ten patients of locally advanced head-and-neck cancer, 6 oropharynx, 3 larynx, and 1 hypopharynx underwent computed tomography (CT) simulation before treatment and after 4 weeks during RT treatment. Original plan (OPLAN) was generated based on initial CT scan for the entire course of treatment. The initial plan is implemented on the second planning CT scan, and the dose distribution is recalculated. Beam configuration of OPLAN was applied onto the second CT scan and then hybrid plan (HPLAN30) was generated. RPLAN30 is the intensity-modulated RT replan generated on the second CT scan for the remaining 30 Gy. Dose and volume parameters between OPLAN30 (based on the first CT scan for the remaining 30 Gy), HPLAN30, and RPLAN30 were compared. Results: The volume reduction of planning target volume (PTV), ipsilateral and contralateral parotid after 4 weeks of RT, was statistically significant (P < 0.05). D2% and V > 107% of PTV were higher in HPLAN than that of RPLAN (P < 0.05). Hybrid plans showed increase in delivered dose to spinal cord. Mid treatment replanning reduced doses to spinal cord (Dmax and D1%), which is statistically significant (P < 0.05). Mean doses to ipsilateral and contralateral parotid of RPLAN (21.4 Gy and 16.74 Gy, respectively) were reduced when compared to that of HPLAN (22.99 Gy and 22 Gy, respectively). Conclusion: Interim CT scanning and replanning (adaptive) improves target volume coverage and normal tissue sparing
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Objectives: To document the dose received by brachial plexus (BP) in patients treated with intensity-modulated radiotherapy (IMRT) for head-and-neck squamous cell carcinoma (HNSCC) and report the incidence of brachial plexopathy. Methods: Newly diagnosed patients of HNSCC treated with radical or adjuvant IMRT were included in this retrospective study. No dosimetric constraints were applied for BP maximum dose equivalent dose (EQD2 α/β = 3). Patients with minimum 6-month follow-up were included and patients with suspicion of plexopathy were evaluated further. Results: Sixty-seven patients were eligible and 127 BP were analyzed. The mean BP maximum dose (BPmax) was 62.4 Gy (+6.9), while mean BP volume was 28.1 cc (+4.1). Proportion of patients receiving BPmax >66 and >70 Gy were 34.7% and 14.2%. The mean BPmax for T4 tumors was significantly higher than T1 tumors (65 vs. 57.5 Gy, P = 0.005) but when adjusted for N-category, T-category was not independently significant in accounting for BPmax >66 or >70 Gy. Mean BPmax for N0 versus N2+ was 59.8 versus 65.6 Gy (P = 0.0001) and N1 versus N2+ was 61.6 versus 65.6 Gy (P = 0.018). After adjusting for T-category, patients with N2+ had a mean 4.2 Gy higher BPmax than N0-N1 (P = 0.0001). Stage III–IV patients had a mean six Gy higher BPmax doses than Stage I–II disease (P = 0.0001). With a median follow-up of 28 months (interquartile range 16–42), no patient had brachial plexopathy. Conclusion: Clinically significant plexopathy was not seen in spite of majority having over 2-years follow-up and a third of patients having dose above the recommended tolerance. Only nodal category independently influenced dose to the brachial plexii
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This study presents an electronic portal imaging devices (EPIDs) based on daily check tool for Linac that is usable for different cancer centers.Several images of open rectangle fields were acquired with EPID and the key items of daily Linac check were derived from the obtained images using an in-house developed automatic analysis software.The experiment results showed that each parameter calculated by this tool is as reliable as the corresponding result measured by the commercial quality assurance devices and its measuring efficiency is much higher.
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Electronics, Medical , Electrons , Particle Accelerators , Phantoms, Imaging , Radiometry , SoftwareABSTRACT
Objective To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy ( SBRT ) plans, and to investigate the sensitivity of the result to three factors:interpolation of measured data, size of dose calculation grid and assessment threshold. Methods The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation ( 1. 00 mm) and non-interpolation ( 7. 62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i.e., 1. 0 mm, 2. 5 mm and 4. 0 mm were compared respectively. The threshold of dose assessment was selected as 10％, 20％ and 30％, respectively. Three criteria of γ analysis were selected: 2％/2 mm, 3％/2 mm and 3％/3 mm. Results Under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, the average γ passing rates were (86. 3±7. 3)％ and (93. 7±5. 6)％, (94. 1±4. 4)％ and(97. 7±3. 9)％, (97. 7 ±2. 2)％ and (99. 1±1. 7)％, respectively, with and without linear interpolation. Relative to the 1. 0 mm reference grid, the grids of 2. 5 mm and 4. 0 mm significantly decreased γ passing rates by 3. 8％, 1. 9％, 0. 8％ ( t=8. 41, 9. 06, 5. 30, P<0. 05) and by 6. 5％, 6. 0％, 3. 5％ ( t=-13. 76, -13. 15, -9. 80, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Relative to the 10％ reference threshold, the shresholds of 20％ and 30％ significantly decreasedγpassing rates by 2. 4％, 1. 0％, 0. 6％(t=-8. 60, -5. 86, -4. 68, P<0. 05) and by 4. 0％, 1. 7％, 0. 9％ (t=-9. 45, -6. 66, -5. 06, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Conclusions Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients.
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Objective To analyze the dosimetric effect of inconsistent bladder filling states between the CT simulation and treatment for prostate cancer patients undergoing intensity-modulated radiotherapy (IMRT).Methods A total of 42 prostate cancer patients treated with IMRT were selected.After vacuum pad immobilization and simulation CT scan,the delineation of targets and organs-at-risk (OARs),treatment planning and dose calculation were performed on treatment planning system (TPS).The cone-beam-CT (CBCT) acquired before the first treatment was registered to planning CT,on which the target contours were duplicated and OARs were delineated.After dose recalculation on the CBCT using the same plan,the dosimetric differences on the CT and CBCT were compared,including mean dose of the planning target volume (PTV),homogeneity index (HI),conformity index (CI);the mean dose,V30,V40,V50,V60,and V65 of bladder and rectum respectively.Results Relative to the bladder volumes at simulation,the patients were divided into two groups with larger (15 cases) or smaller (27 cases) bladders at the first treatment.Comparing the parameters obtained from simulation CT with that from CBCT,the differences of the following parameters were of statistical significance:the bladder volume,PTV HI,PTV CI in both groups (t =6.838,-4.372,-3.553,-3.462,6.380,5.037,P＜ 0.05),the bladder V30,V40,V50,V60,V65(t=-5.004,-4.092,-3.124,-2.707,-2.489,P ＜0.05) and rectal V40,V50,V60,V65,mean dose in the group with smaller bladders (t=-2.946,-2.643,-2.426,-3.127,-2.530,P ＜ 0.05),and the bladder V30,V40,V50 and mean dose in group with larger bladders (t =5.107,4.204,3.777,4.155,P＜0.05).Conclusions For prostate cancer patients undergoing IMRT,the inconsistent bladder filling states between the planning and treatment will cause disimetric differences of targets and OARs.
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Objective@#To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy (SBRT) plans, and to investigate the sensitivity of the result to three factors: interpolation of measured data, size of dose calculation grid and assessment threshold.@*Methods@#The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation (1.00 mm) and non-interpolation (7.62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i. e., 1.0 mm, 2.5 mm and 4.0 mm were compared respectively. The threshold of dose assessment was selected as 10%, 20% and 30%, respectively. Three criteria of γ analysis were selected: 2%/2 mm, 3%/2 mm and 3%/3 mm.@*Results@#Under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, the average γ passing rates were (86.3±7.3)% and (93.7±5.6)%, (94.1±4.4)% and(97.7±3.9)%, (97.7 ±2.2)% and (99.1±1.7)%, respectively, with and without linear interpolation. Relative to the 1.0 mm reference grid, the grids of 2.5 mm and 4.0 mm significantly decreased γ passing rates by 3.8%, 1.9%, 0.8% (t=8.41, 9.06, 5.30, P<0.05) and by 6.5%, 6.0%, 3.5% (t=-13.76, -13.15, -9.80, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively. Relative to the 10% reference threshold, the shresholds of 20% and 30% significantly decreased γ passing rates by 2.4%, 1.0%, 0.6%(t=-8.60, -5.86, -4.68, P<0.05) and by 4.0%, 1.7%, 0.9% (t=-9.45, -6.66, -5.06, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively.@*Conclusions@#Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients.