Objective To evaluate the dosimetric impact from collimator angles during the VMAT planning for upper thoracic esophageal carcinoma.Methods VMAT plans for 8 cases of upper thoracic esophageal were studied.Ten different plans with respective collimator angles (0,5,10,15,20,25,30,35,40,45 degrees) were determined for each case,and the treatment planning parameters were compared.Results The 20 degree group represented with best performance,and 0 and 45 degree group were most frequently used in clinical practice.Statistical analysis shown that among these groups,V10,V15 and V30of total lung were significantly different (F =5.328,8.033,28.424,P ＜ 0.05),and differences of maximal dose of spinal cord and total MU were also significant (F =9.608,4.464,P ＜ 0.05).Conclusions A proper collimator angle is important in VMAT planning for upper thoracic esophageal and may lead to optimal results.

Objective To study the accuracy of collapsed cone convolution ( CCC) and anisotropic analytical algorithm ( AAA) in dosimetric calculation on the air cavity interface. Methods A BEAMnrc/EGSnrc Monte Carlo ( MC ) simulation was performed on a Varian Trilogy linear accelerator. The IBA Dosimetry “blue phantom” 3D scanning system was used to verify the accuracy and reliability of the MC simulation. Central axis depth dose distribution and lateral dose profile in a water?equivalent phantom with variously sized air cavities were calculated by CCC and AAA. The obtained depth dose distribution and lateral dose profile were compared with those by MC simulation and EBT2 film, respectively. Results Both CCC and AAA overestimated the dose on the air cavity interface. In spite of some errors, CCC had a higher accuracy than AAA. The errors were mainly related to computational grid, field size, photon energy, cavity size, and the number of fields. Conclusion Electronic disequilibrium on the air cavity interface should be taken into account when CCC and AAA are used for dosimetric calculation in treatment planning system.

Objective To retrospectively design an intensity?modulated radiotherapy ( IMRT) plan with split field and fixed jaw techniques for peripheral lung cancer with mediastinal lymph node metastasis, to compare dosimetric characteristics between the IMRT plans with fixed jaw and dynamic jaw, and to study lung protection by the plan with split field and fixed jaw. Methods Treatment plans were collected from 12 patients with peripheral lung cancer and mediastinal lymph node metastasis who were treated with IMRT in our hospital. All plans used the dynamic jaw technique. The plans with split field and fixed jaw were designed based on the identical computed tomography images and planning target volume ( PTV) . Each jaw position in split field depended on each separate PTV. The prescription dose was 60 Gy in 30 fractions. 95%PTV was planned to receive 100% of the prescription dose. Dosimetric parameters of PTV, conformity index ( CI) , heterogeneity index ( HI) , number of monitor units ( MUs) , and dose?volume values of the lung and heart were obtained from dose?volume histogram. Comparison between the two plans was made by paired t test. Results Both plans met clinical requirements. There were no significant differences in D2 , D98 , CI, or HI of PTV between the two plans ( all P>005) . Compared with the dynamic jaw plan, the fixed jaw plan had MUs increased by 15%?20%( P=0010) . The V5 , V10 , V20 , V30 , and mean dose for the whole lungs were significantly lower in the fixed jaw plan than in the dynamic jaw plan ( P=0000, 0000, 0000, 0002,0000) . The V5 , V20 , and mean dose for the healthy lung were also significantly lower in the fixed jaw plan than in the dynamic jaw plan ( P=0000,0017,0000) . There were no significant differences in dose?volume values for the spinal cord or heart between the two plans ( all P>005) . Conclusions IMRT with split field and fixed jaw is recommended for patients with peripheral lung cancer and mediastinal lymph node metastasis. The therapy to a certain extent reduces low?dose volume for the lung and the incidence of radiation?induced pneumonitis.

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.

With the development of technology, several treatment plans can be got easily. There are many parameters related to the treatment in each plan and it is not only complex but also time-consuming to analyze them. So it is difficult for radiation oncologists to choose a plan. In order to solve the problem, a fast tool was developed integrating parameters such as conformity index and homogeneity index. This paper reviewed the type development, formula and features of conformity index and homogeneity index, in order to provide reference for users.

Objective To analyze the relationship between planning factors of intensity-modulated radiation therapy (IMRT) and gamma index and investigate the effect of each parameter upon the γ passing rate of IMRT.Methods Gamma analysis was performed using 3％/3 mm acceptance criteria for 457 IMRT beams with different planning factors.During multi-factor ANOVA analysis of planning factors and gamma passing rate,the control variables primarily included the minimum segment area,minimum number of monitor unit (MU),number of segment,segment conversation,and the spatial resolution in the measured dose distribution.Results The percentage of pixels with passingγsignificantly differed under different minimum segment area,segment conversation and the spatial resolution in the measured dose distribution (all P＜ 0.05).No significant correlation was observed between the passing rate and the minimum number of MU and the number of segment (P＞ 0.05).Conclusions According to the actual situation of the equipment,the minimum segment area should be determined during IMRT planning.Direct machine parameter optimization should be performed.Appropriate resolution of the plane dose images can be chosen according to the minimum detector interval of dose matrix device,

ViewRay magnetic resonance (MR) guided radiotherapy system not only solves the problem of imaging dose,but also can set up accurately,online adaptive radiotherapy and gated irradiation according to magnetic resonance imaging (MRI).The development of this system provides a new technical means of accurate radiotherapy.This review describes the main structure of the ViewRay system,and summarizes quality assurance (QA),dosimetric comparison,respiratory motion management,online adaptive radiotherapy,and preliminary treatment effect.

The mortality rate of lung cancer is relatively high and the incidence of lung cancer has been increased year by year.Consequently,early screening and diagnosis plays a crucial role.The traditional screening method is biopsy,which has multiple defects.Radiomics can resolve these limitations and improve the diagnosis and prognosis of lung cancer in a noninvasive and low-cost manner,assisting the clinicians to make decisions in clinical practice.In this paper,the process and application,prospects and challenges of radiomics in the screening of lung cancer were introduced,aiming to promote the development of radiomics.