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Objective:To evaluate the practicability of dose volume histogram (DVH) prediction model for organ at risk (OAR) of radiotherapy plan by minimizing the cost function based on equivalent uniform dose (EUD).Methods:A total of 66 nasopharyngeal carcinoma (NPC) patients received volume rotational intensity modulated arc therapy (VMAT) at Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences from 2020 to 2021 were retrospectively selected for this study. Among them, 50 patients were used to train the recurrent neutral network (RNN) model and the remaining 16 cases were used to test the model. DVH prediction model was constructed based on RNN. A three-dimensional equal-weighted 9-field conformal plan was designed for each patient. For each OAR, the DVHs of individual fields were acquired as the model input, and the DVH of VMAT plan was regarded as the expected output. The prediction error obtained by minimizing EUD-based cost function was employed to train the model. The prediction accuracy was characterized by the mean and standard deviation between predicted and true values. The plan was re-optimized for the test cases based on the DVH prediction results, and the consistency and variability of the EUD and DVH parameters of interest (e.g., maximum dose for serial organs such as the spinal cord) were compared between the re-optimized plan and the original plan of OAR by the Wilcoxon paired test and box line plots.Results:The neural network obtained by training the cost function based on EUD was able to obtain better DVH prediction results. The new plan guided by the predicted DVH was in good agreement with the original plan: in most cases, the D 98% in the planning target volume (PTV) was greater than 95% of the prescribed dose for both plans, and there was no significant difference in the maximum dose and EUD in the brainstem, spinal cord and lens (all P>0.05). Compared with the original plan, the average reduction of optic chiasm, optic nerves and eyes in the new plans reached more than 1.56 Gy for the maximum doses and more than 1.22 Gy for EUD, and the average increment of temporal lobes reached 0.60 Gy for the maximum dose and 0.30 Gy for EUD. Conclusion:The EUD-based loss function improves the accuracy of DVH prediction, ensuring appropriate dose targets for treatment plan optimization and better consistency in the plan quality.
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Objective To explore the value of generalized equivalent uniform dose (gEUD) optimization in radiotherapy for chest malignant tumors. Methods Sixty patients with chest malignant tumors who were treated in Center for Tumor Radiotherapy, Chizhou Municipal People’s Hospital, Anhui Province, China from October 2021 to June 2022 were enrolled; each patient underwent tumor localization with a conventional fixed computed tomography scan. The patients were divided into two groups using the same field direction and weight in the Varian Eclipse 15.6 planning system. The first group was planned using the conventional physical dose-volume objective function plus the Upper gEUD objective function, with organs at risks (OARs) optimized with the EUD values suggested by the Varian Eclipse 15.6 planning system. The second group only adopted the conventional physical dose-volume objective function for OARs optimization. The two groups were compared for the radiation doses delivered to the OARs. Results Compared with the conventional physical dose-volume objective function alone, the addition of Upper gEUD objective function resulted in no significant difference in lung V5Gy, but resulted in significant reductions in V20Gy and mean dose in the lungs; some reductions in V30Gy, V40Gy, and mean dose in the heart; and significant reductions in the maximum dose in the spinal cord. Conclusion The gEUD objective optimization can effectively protect the normal tissue in the radiotherapy for chest malignant tumors and thus is recommended in radiotherapy planning.
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Objective To compare the dosimetric difference between the biological function based on equivalent uniform dose (EUD) and the physical function based on dose volume (DV) in the intensity modulated radiotherapy for stage Ⅲ non-small cell lung cancer. Methods Four different radiotherapy plans were designed for 15 stage Ⅲ non-small cell lung cancer patients: Group A, physical function optimization (DV + DV) was used for target area and organs at risk; GroupB, in the target region, biological function optimization conditions were added on the basis of physical function optimization, and physical function optimization of organs at risk (DV－EUD + DV) was added. Group C, biological function optimization (EUD + EUD) was used for target area and organs at risk. Group D, in the target area, physical function optimization conditions were added on the basis of biological function optimization, and biological function optimization of organs at risk (EUD－DV + DV) was added. The differences in dosimetric parameters of the four plans were compared. Results Target area: PTV: D2%, D98%, D50%, D105% and Dmax values of group C (P < 0.05) is the highest while group B and group D were relatively small (P > 0.05); The homogeneity index: the results of the group B and the group D were better than those of the other two groups (P < 0.05). conformity index: The results of the four groups were similar (P>0.05). Organ at risk: lung tissue mean dose (MLD), V5, V10, V20, V30 and heart V30, V40, Dmean dose parameters were similar (P > 0.05). Spinalcord: Group C and group D D1% were better than the other two groups (P < 0.05). There was no statistical difference in the number ofmonitor unit (MU) among the four groups (P > 0.05). Conclusion The optimization method combining physical and biological function optimization in the target area can improve the conformity of the target area on the premise of ensuring the treatment. The Spinalcord load would be significantly reduced when using biological function optimization or the combination of biological function and physical function optimization.
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Objective To propose a treatment planning optimization algorithm which can make full use of OAR dose distribution prediction meanwhile improving the output planning quality as much as possible.Methods We had reformulated an FMO function under the guidance of dose distribution prediction and also integrated equivalent uniform dose (gEUD) based on the consideration of prediction uncertainty,for providing optimal solution.Performance of the method was evaluated by comparing the optimized IMRT plan quality of 8 cervical cancers in the term of DVH curves,dose distribution and dosimetric endpoints with the original ones.Results The proposed method had a feasible,fast solution.Compared with original plan,its output plan had better plan quality in better dose homogeneity,less hot spot and further dose sparing for OARs.V30,V45 of rectum was decreased by (6.60±3.53)％ and (17.03±7.44)％,respectively,with the statistically significant difference (t=-4.954,-6.055,P＜0.05).V30,V45 of bladder was decreased by (14.74 ± 5.61) ％ and (14.99 ± 4.53) ％,respectively,with the statistically significant difference (t=-6.945,-8.759,P＜0.05).Conclusions We have successfully developed a predicted dose distribution and equivalent uniform dose-based planning optimization method,which is able to make good use of 3D dose prediction and ensure the output plan quality for intensity modulated radiation therapy.
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Objective To discuss the dosimetric differences in the planning methods between physical and biological optimization during thehypofractionated radiotherapy for lung cancer.MethodsTen cases of non-small cell lung cancer (NSCLC) receiving radiotherapy were selected in this retrospective study.The VMAT plans for all patients were re-designed by physical functions (DV group),biological combined with physical functions (DV+EUD group and EUD+DV group) and biological functions (EUD group).The constrained functions were different,whereas the constrained conditions and optimized parameters were identical among four groups.The dosimetric differences among four optimization methods during thehypofractionated radiotherapy for lung cancer were evaluated through calculating and analyzing each dosimetry parameter.Results For the target area,the equivalent uniform dose was approximate between the EUD and EUD+DV groups.The EUD in these two groups was approximately 2.8％-3.6％ and 3.2％-3.7％ higher than those in the DV and DV+EUD groups.The average tumor control probability (TCP) in the EUD and EUD +DV groupswas considerably higher than those in the other two groups (both P＜0.05).The homogeneity index (HI) significantly differed (all P＜0.05),whereas the conformity index (CI) did not differ (all P＞0.05).For the organ at risk (OAR) area,the differences of EUD,V5,V1o,V20,V30 of normal lung tissues and the difference of dosimetry parameters in heart and spinal cord were not statistically significant (all P＞0.05).The mean dose of all lungs in the EUD and EUD+DV groupswas slightly lower than those in the other two groups.ConclusionsBiological optimization method has certain advantages in increasing EUD and TCP in the target area and decreasing the irradiation dose of normal lung tissues,which provides references for selecting the optimization method with biological functions in clinical practice.
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Background and purpose: The literature on dose-volume parameters and pneumonitis is extensive. The results are inconsistent, both for the best predictive metrics and significant comorbid factors. This study aimed to investigate a prospective functional equivalent uniform dose (fEUD) with perfusion single photon emission computed tomography (SPECT) images as predictors of radiation pneumonitis (RP) in patients undergoing curative radiotherapy (RT). Methods: Functional lung imaging was performed using SPECT for perfusion imaging. Perfusion factors were defined as the mean percentile perfusion levels of the 4 areas, top to 75%, 75% to 50%, 50% to 25%, 25% to 0%, re-spectively. fEUD was calculated from perfusion factors and standard dose-volume parameters extracted from treatment planning computed tomography (CT) scans. Total lung (TL), ipsilateral (IL) and contralateral lung (CL) volumes minus gross tumor volume (GTV), whole-lung V5, V20, whole lung fEUD, IL and CL fEUD, and general equivalent uniform dose (gEUD) were analyzed to evaluate correlations between RP using Common Terminology Criteria for Adverse Events (CTCAE) version 4.03. Statistical significance was defined as P<0.05. Results: A total of 15 patients treated with intensity modulated RT or 3D conformal RT were analyzed, grades≥3 RP were observed in 6 patients. There was only a trend toward significance for unilateral (UL) fEUD of higher dose side (P=0.007). Whole-lung V5, V20 were almost identical between patients who developed pneumonitis and patients who did not, as the values were below the recommended thresholds from published papers. Unilateral fEUDs were linear with unilateral gEUDs (t=0.815, P=0.000). Conclusion: SPECT-based equivalent uniform dose appears to be a better predictor of RP compared to stan-dard dose-volume parameters. Planning constraints should aim to keep unilateral fEUD below 21 Gy.
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Objective To evaluate the role of equivalent uniform dose (EUD) in planning optimization of intensity-modulated radiotherapy (IMRT) for prostate cancer.Methods Ten patients with prostate cancer were randomly selected who treated with IMRT.For these patients,the treatment plans were designed with dose-volume objectives.Based on these plans,new plans were designed through replacing the dose-volume objectives with maximum EUD for rectum,bladder and small bowel,while keeping the dosevolume objectives unchanged.Comparison was made between the new plans and the former cones by paired t-test.Results The conformity index of planning target volume was better with EUD optimization compared to dose-volume (1.00 ± 0.04 ∶ 0.94 ± 0.04,t =3.80,P =0.04).The D53,D30 and Dicm3 for rectum was better with EUD optimization compared to dose-volume (24.4 ± 2.7 ∶ 25.5 ± 2.6,t =-3.82,P =0.004,34.1 ±4.3∶39.1±2.1,t=-3.80,P=0.004 and51.4±1.0∶51.8±0.9,t=-2.42,P=0.039),with V10,V20 for bladder and V10,V20,V30,V40 for small bowel also better with EUD optimization (92.2 ±6.2∶99.4±1.1,t=-4.28,P=0.002;70.7±5.7∶78.7±6.3,t=-3.10,P=0.013 and 62.2±30.2∶74.7 ±30.0,t =-4.18,P =0.002;34.3 ±26.3∶46.5 ±30.9,t =-5.46,P =0.000;17.1 ±17.0∶25.1 ±22.6,t=-3.52,P=0.007;10.6± 11.5∶ 15.6± 16.1,t=-2.64,P=0.030).Conclusions The conformity index of planning target volume is better with EUD optimization compared to dose-volume.And the dose to rectum,bladder and small bowel can be reduced through optimization with EUD optimization compared to dose-volume.
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The applicability and feasibility of TomoTherapy in the lung radiation surgery was analyzed by comparison of the calculated dose distribution in TomoTherapy planning with the results of conventional IMRS (intensity modulated radiation surgery) using LINAC (linear accelerator). The acquired CT (computed tomograph) images of total 10 patients whose tumors' motion were less than 5 mm were used in the radiation surgery planning and the same prescribed dose and the same dose constraints were used between TomoTherapy and LINAC. The results of TomoTherapy planning fulfilled the dose requirement in GTV (gross tumor volume) and OAR (organ at risk) in the same with the conventional IMRS using LINAC. TomoTherapy was superior in the view point of low dose in the normal lung tissue and conventional LINAC was superior in the dose homogeneity in GTV. The calculated time for treatment beam delivery was long more than two times in TomoTherapy compared with the conventional LINAC. Based on the results in this study, TomoTherapy can be evaluated as an effective way of lung radiation surgery for the patients whose tumor motion is little when the optimal planning is produced considering patient's condition and suitability of dose distribution.