ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
PURPOSE: The objective of this study was to compare dosimetric characteristics of three-dimensional conformal radiotherapy (3D-CRT) and two types of intensity-modulated radiotherapy (IMRT) which are step-and-shoot intensity modulated radiotherapy (s-IMRT) and modulated arc therapy (mARC) for thoracic esophageal cancer and analyze whether IMRT could reduce organ-at-risk (OAR) dose. MATERIALS AND METHODS: We performed 3D-CRT, s-IMRT, and mARC planning for ten patients with thoracic esophageal cancer. The dose-volume histogram for each plan was extracted and the mean dose and clinically significant parameters were analyzed. RESULTS: Analysis of target coverage showed that the conformity index (CI) and conformation number (CN) in mARC were superior to the other two plans (CI, p = 0.050; CN, p = 0.042). For the comparison of OAR, lung V5 was lowest in s-IMRT, followed by 3D-CRT, and mARC (p = 0.033). s-IMRT and mARC had lower values than 3D-CRT for heart V30 (p = 0.039), V40 (p = 0.040), and V50 (p = 0.032). CONCLUSION: Effective conservation of the lung and heart in thoracic esophageal cancer could be expected when using s-IMRT. The mARC was lower in lung V10, V20, and V30 than in 3D-CRT, but could not be proven superior in lung V5. In conclusion, low-dose exposure to the lung and heart were expected to be lower in s-IMRT, reducing complications such as radiation pneumonitis or heart-related toxicities.
Subject(s)
Humans , Esophageal Neoplasms , Heart , Lung , Radiation Pneumonitis , Radiotherapy , Radiotherapy, Conformal , Radiotherapy, Intensity-ModulatedABSTRACT
Objective To compare the dosimetric differences in heart and lung among three radiotherapy techniques in the treatment of thoracic esophageal cancer. Methods A total of 15 thoracic esophageal cancer patients treated in Zhejiang Cancer Hospital during the period of January 2015 to February 2016 were enrolled in this retrospective dosimetric study. Three radiotherapy treatment plans, including intensity-modulated radiotherapy ( IMRT) , volumetric intensity modulated arc therapy ( VMAT) with Raystation 4. 0v TPS, and tomotherapy (TOMO) plans with TomoTTM v2. 0. 5 TPS were generated for each patient with a prescribed dose of 60 Gy at 2 Gy per fraction. Dosimetric differences in planning target volume ( PTV) , heart, cardiac subunits and lung were compared. Results The mean volumes of PTV, heart and lung were (399 ±355), (671 ±274) and (3907 ±1717)cm3, respectively. Compared with VMAT and IMRT, TOMO reduced the maximum dose of PTV, heart, left atrium and lung ( H=10. 889, 7. 433, 12. 080, 11. 401, P <0. 05). No difference was observed in conformity or homogeneity among these three plans. Conclusions TOMO reduced the maximum dose to PTV, heart, left atrium and lung compared with VMAT and IMRT, However, no difference in conformity and homogeneity was observed. The impact of dosimetric advantage of TOMO needs further verification due to the interaction between heart and lung for thoracic esophageal cancer patients.
ABSTRACT
Objective To perform a systematic review and Meta-analysis on volumetric and dosimetric changes in target volumes and organs at risk (OARs) in adaptive radiotherapy (ART) for patients with head and neck cancer (HNC),and to investigate the role of ART in the treatment of HNC.Methods Literature retrieval was performed to include related studies,and the parameters of primary tumor,GTV-T and GTV-N,parotid volume,D95 and Dmean of target volumes,Dmean of ipsilateral and contralateral parotid volume (I-PG and C-PG),and Dmax of the spinal cord and brainstem.Results A total of 17 studies involving 336 patients were included in the meta-analysis.Primary tumor and parotid volume changed significantly.The volumes of GTV-T,GTV-N,and I-PG were significantly reduced during the 15-20th radiotherapy and after the 20th radiotherapy (P＜0.05),and the C-PG was significantly reduced after the 20th radiotherapy (P=0.004).The analysis of actual dose showed that the D95 and Dmean of primary tumor showed no significant differences,and during the 15-20th radiotherapy,the Dmax of the spinal cord was increased by 2.26 Gy (P=0.000),while the Dmax of the brainstem showed no significant changes before the 20th radiotherapy and was increased by 1.78 Gy after the 25th radiotherapy (P=0.020).In addition,the Dmean of I-PG was increased by 2 Gy during the 20-25th radiotherapy (P =0.0001),and the D of C-PG was increased before the 20th radiotherapy and showed no significant changes after the 25thradiotherapy (P=0.110).The dosimetric analysis of ART showed that the Dmax of the spinal cord and brainstem was reduced significantly (spinal cord:MD =-2.15,95％ CI-3.12 to-1.18,P=0.000;brainstem:MD =-2.20,95％ CI-3.32 to-1.09,P=0.000).The Dmean of I-PG was reduced by about 3.5 Gy,and the sensitivity analysis revealed that the results of Dmean of C-PG were unstable.Conclusions The volumes of primary tumors and parotid glands change significantly,and the actual doses of OARs (Dmax of the spinal cord and brainstem and Dmean of the parotid glands) significantly increase,while the doses of GTV-T and GTV-N show no significant changes.ART can effectively protect the OARs,and patients with locally advanced HNC who receive concurrent chemoradiotherapy can obtain good dose gains from ART plan performed during the 15-20th radiotherapy and at about the 25th radiotherapy.
ABSTRACT
Obejctive To compare the differences between conventional radiation therapy (3DCRT) and intensity modulated radiation therapy( IMRT) for locally advanced laryngeal carcinoma patients by ECLIPSE treat -ment planning system.Methods Six locally advanced laryngeal carcinoma patients ′treatment plans were de-signed as IMRT and 3DCRT according to ECLIPSE treatment planning system ,respectively.The following values were measured,such as V95%、D5%、D95%、Dmin and D mean of the target volume,and the D50,D33,D5, Dmax and Dmean of normal tissues.Results The dose coverage rate of GTV and GTVnd in the IMRT plan was compared to ECLIPSE treatment planning system with no statistical differences.However, there were obvious difference in CTV and some normal tissues.Conclusion Both IMRT and 3DCRT have good coverage to primary tumor and metastatic lymph nodes.IMRT can spare the parotid from high dose irradiation.
ABSTRACT
Objective To compare the dose distribution between three dimensional conformal radiothera -py(3DCRT) and simplified intensity modulated radiotherapy ( sIMRT) for middle-third esopheagal cancer .Meth-ods Twenty middle-third esopheagal cancer patients were enrolled in this study .Dosimetric values for sIMRT and 3DCRT were calculated for total dose of 66 Gy using 2 Gy/day.The parameters included the conformal index (CI),homogeneity index(HI),mean dose and hot spot(V105%)for the planned target volume(PTV)as well as the monitor units(MUs)for plan efficiency,the mean dose(Dmean)for the organs at risk(OAR).The percentage of the normal lung volume receiving≥30,>20 and >5 Gy(V30 Gy,V20 Gy and V5 Gy)were evaluated to deter-mine lung toxity.Results sIMRT achieved significant better Dmin ,Dmean,V105%,HI,CI and spinal cord than 3DCRT(P<0.05).The normal lung V30 Gy and V20 Gy of 3DCRT and sIMRT were 11.61 ±3.68 vs.10.33 ± 3.02(P=0.010)and 23.37 ±8.38 vs.18.89 ±4.45(P=0.001),respectively.Comparable sparing of normal tissue including heart and the normal lung V 5 Gy with both two plans .The number of MU was 542 .24 ±76 .32 for 3DCRT and 530.8 ±97.13 for sIMRT(P=0.677).Conclusion sIMRT provides favorable tumor coverage , homogeneity and conformity and can get better normal lung sparing than 3DCRT.However sIMRT is not superior to 3DCRT in terms of treatment efficiency .