Objective To compare the dosimetry of three different radiation therapy plans [threedimensional conformal radiation therapy (3DCRT),intensity modulated radiation therapy (IMRT),intensity modulated arc radiotherapy (IMAT)].Methods Selected 15 cases with middle thoracic esophageal cancer,Varian Eclipse 8.6 planning systems were designed with 3DCRT,IMRT,IMAT,3DCRT using 5-8 coplanar radiation fields,IMRT using 7 coplanar radiation fields,IMAT using 2 radians.Three planned dose difference were compared.Results Compared with 3DCRT,IMRT and IMAT were better with heterogeneity index (HI),conformality index (CI),VPTV 95 ％,V5,V20,V35 of total lung,and V30 of heart (t =2.531,P＜ 0.05).There was no statistically significant difference for the V10,V15,V25,V30 mean dose of total lung,the mean dose of heart,the maximum dose of spinal cord,and the minimum dose of PTV among the three plans (t =1.325,P ＞0.05).Conclusion IMAT and IMRT are similar in the middle thoracic esophageal cancer radiotherapy target volume dose coverage and organs at risk protection,they are better than 3DCRT.IMAT in the monitor units and delivery time are less than IMRT.

Objective To evaluate the validity of narrow-band imaging (NBI) system in detection of colorectal adenoma, as compared to that of endoscopy of the colon and rectum, in a systematic review. Methods Relevant literatures were retrieved from Medline (January 1966 to October 2008), OVID (January 1996 to October 2008), EMBASE (January 1980 to October 2008), Coehrane Library (Issue 3, 2008) and Chinese Biological Medicine Disk (CBM disk, January 1997 to October 2008). Quality of the literatures retrieved was assessed based on the Cochrane Reviewers' Handbook and Jadad's score. RevMan version 4. 2 software was used for meta-analysis. Results Seven randomized clinical trials (2838 patients) were included in the study. Compared with white-light colonoscopy, no significant difference was observed in terms of adenoma detection rate (OR 1.18, 95% CI 1.00-1.39, P=0.06) by NBI system, which could significantly improve total number of detection for fiat lesions of the colon and rectum (pooled WMD 0.14, 95% CI 0.02-0.26, P=0.02), but with a longer withdrawn time (pooled WMD 1.05, 95% CI 0.08-1.22, P<0.01). Conclusions Detection rate for flat lesions of the colon and rectum, not for adenoma, can be improved by NBI system and meanwhile its withdrawn time is prolonged, indicating that routine use of NBI system for detecting colorectal adenomas may be recommended only with its further refined technique.

Objective Using Eclipse and Pinnacle3 V 7.4f treatment planning sytems (TPS) for dose calculation of the CT images of simulation phantom,patients and homogeneous organization phantom,to compare the differences between the two TPS for the calculation of non-uniform organizations.Methods For the CT images of simulation phantom,patients and homogeneous organization phantom,the calculating results between the two TPS were compared,including the common used clinical indexes of V20 and V30 of the lung,D95 of the planning target volume,the doses of the ISO and eight points of interest inside ISO slice.Resuits For simulation phantom and patients,although the calculating differences of the isocenter doses between the two TPS were small,the differences of other indicators were large.For example,when using secondary collimator irradiation,the maximal D95 difference of planning target volume reached 10.17%for patients and 4.64%for simulation phantom.When using muhileaf collimator irradiation,the maximal D95 difference reached 10.74%for patients and 5.66%for simulation phantom.Sometimes the dose differences of points 1-4 at the edge of planning target volume were more than 10%.In addition,the V30 differences of the lung were large too.But for the homogeneous organization phantom,the calculating differences were small.Conclusions The calculating differences between the two TPS are less for simulation phantom than for patients,and more for simulation phantom and patients than for homogeneous organization phantom.

ObjectiveTo study the efficacy of using multileaf collimators with different position and different degree in the treatment of nasopharyngeal carcinoma (NPC) using intensity-modulated radiotherapy techniques.Methods Ten patients withNPC were administered andanalyzed.Thepenumbra characteristics, dose of target, and radiation conformal indexes (CI) of mode T1 and mode T2 were measured and compared using dose volume histogram generated by Varian Eclipse three-dimensional planning computer system. Mode T1 :The angles of seven coplanar beams were 0°, 52°, 106°, 160°, 212°, 258°and 308°,respectively. There were no restriction on the position and degree of multileaf collimators. Parameters were set and optimized. Mode T2 :The beam angles and the parameters were as same as mode T1. According to the actual situations, the position and the degree of the multileaf collimators were changed. Then thedose optimization was performed. Results Target dose coverage in both mode T1 and T2 could be clinically accepted, and the CI were 0. 82 and 0. 83(t = -0. 25, P =0. 815). The maximum dose reductions in the lens, eyes, optic nerves and corneas were 28. 7% (t = 4. 80, P = 0. 000), 2. 7% (t = 2. 99, P = 0. 021),1.4%(t= 1.05,P=0.032), and 30.5% (t=2.99,P=0. 020), respectively. However, the mean dose and V35 of the parotid were increased by 0. 6% (t = - 2. 82, P = 0. 043) and 9.9% (t = - 2. 05, P =0. 038). ConclusionsOpimization of multileaf collimators can reduce the scattering and leaking rays. Compared with mode T1 ,controlling the position and degree of multileaf collimators could reduce the radiation dose to the eyes and optic-nerves, especially to the lens.

0.05).The variced recurrence rate in 1- and 2-year were 12% (3/25) and 20% (5/25) in TH glue group,and 39.1% (9/23) and 86.9%(20/23) in control group (P

Objecttve To compare the positional and volumetric differences of planning target volumes(PTVs)based on axial three-dimensional CT(3D-CT)and four-dimensional CT(4D-CT)for the primary tumor of non-small cell lung cancer(NSCLC).Methods Sixteen NSCLC patients with lesions located in the upper lobe and 12 patients with lesions in middle and lower lobes,totally 28 patients, initially underwent three-dimensional CT scans followed by 4D-CT scans of the thorax under normal free breathing.PTVvector was defined on gross tumor volume (GTV) contoured on 3D-CT and its motion vector. The clinical target volumes(CTVs)were created by adding 7 mm to GTVs,then, internal target volume (ITVs)were produced by enlarging CTVs isotropically based on the individually measured amount of motion in the 4D-CT,lastly,PTVs were created by adding 3 mm setup margin to ITVs. PTV4D was defined on the fusion of CTVs on all phases of the 4D data.The CTV wag generated by adding7 mm to the GTV on each phase.then,PIVs were produced by fusing CTVs on 10 phases and adding 3 mm setup margin.The position of the target center,the volume of target and the degree of inclusion(DI)were compared reciprocally between the PTVvector and the PTV 4D The difference of the position,volume and degree of inclusion of the targets between PTVvecter and PTV4D were compared,and the relevance between the relative characters of the targets and the three-dimensional vector was analyzed based on the groups of the patients. Results The median of the 3 D motion vector for the lesions in the upper lobe was 2.8 mm, significantly lower than that for the lesions in the middle and lower lobe ( 7.0 mm, z = - 3. 485, P < 0. 05 ). In the upper lobe group there was only significant spatial difference between the PTVvector and PTV4D targets in the center coordinate at the x axe (z = -2. 010, P < 0. 05 ), while in the middle and lower lobes there was only significant spatial difference between the PTVvector and PTV4D targets in the center coordinates at the z axe (z = -2. 136,P <0.05). The median of ratio of PTV4D and PTVvector, of the upper lobe group was 0. 75, significantly higher than that of the middle and lower lobes group (0. 52, z = - 2. 949, P < 0. 05 ).A significant correlation was found for the motion vector and the ratio of PTV and PTV4D in both groups ( r = - 0. 638, - 0. 850, P < 0. 05 ). For all patients, the median of D[ of PTV4D in PTVvector was 66. 39% ,while the median of DI of PTVvector, in PTV4D was 99. 55% , both showed a positive significant correlation with the motion vector (r = -0. 814,0. 613 ,P < 0. 05). Conclusions PTV4D defined based on 4D-CT simulation images is obviously less than PTV defined based on 3D-CT simulation images. The ratio and DI of both targets are related with the three-dimensional motion vector of the tumor.

Objective To evaluate the position deviation of multi-leaf collimator (MLC) in volumetric modulated arc therapy for nasopharyngeal carcinoma and to verify a method of detecting the leaf position accuracy.Methods Thirty-two volumetric modulated arc plans of nasopharyngeal carcinoma were randomly selected.A clockwise arc with a gantry range of 181° to 179° and a counterclockwise arc with a gantry range of 179° to 181° were uscd for each plan.Each arc contained two leaf groups,groups A and B.By using the Argus software,the actual MLC leaf positions were extracted from the Dynalog files in the Varian Trilogy accelerator.The planed MLC leaf positions were compared with the actual positions,and the differences were calculated between them.Results The proportions of the leaf position errors within ± 2,± 1.5,± 1 and ± 0.5 mm were 99.99％,99.90％,99.07％ and 93.98％,respectively.The proportions of the leaf position errors within ± 1 mm were 98.08％,100％,98.97％ and 99.01％ for the first therapeutic arc (ARC1),second therapeutic arc (ARC2),A and B groups,respectively.The leaf position errors range of ARC1 and ARC2 were-2.95 to 2.99 and-0.22 to 0.23 mm (t =2.35,P ＜ 0.01).The leaf position errors range of leaf bank A and leaf bank B were-2.95 to 2.68 and-2.92 to 2.99 mm(P ＞ 0.05).Conclusions During the volumetric modulated arc radiotherapy,the leaf positions deviation are in control.The Dynalog files can be used as an effective way to analysis the leafposition errors.

Objective To investigate the variations of the spatial position and overlap ratio of the internal target volume (ITV) and planning target volume (PTV) of primary thoracic esophagus carcinoma using repeated four-dimensional computed tomography (4D-CT) scanning during conventional fractionated radiotherapy.Methods Thirty patients with thoracic esophageal carcinoma were included whose 4D-CT scans were conducted before radiotherapy and between every ten fractions.The gross tumor volumes (GTVs) were delineated by the same radiation oncologist on each 4D-CT image phase,and the ITV and PTV were constructed afterwards.Results No significant difference of the isocenters was observed for the ITV and PTV during the treatment course,yet both the volumes of the ITV and PTV decreased.The median DI (the degree of inclusion) of the target acquired subsequently in the original target were 0.85,0.77 (Z=-3.10,P ＜0.05) for ITV and 0.86、0.82(Z =-2.49,P ＜0.05)for PTV respectively during entire treatment.The variation of volume ratio correlated strongly with the variation of DI (the DI of the target acquired subsequent in the original target) (rITV =0.71,rPTV =0.77,P ＜0.05).The variation of volume ratio and the variation of the matching index (MI) were positively correlated (rITV =0.47,rPTV =0.59,P ＜ 0.05).The 3D vectors of ITV and PTV motions were negatively correlated with the corresponding MI (rITV =--0.52,rPTV =-0.36,P ＜ 0.05).If the initial PTV was used for treatment planning,8.80％ and 6.37％ of the target volume would be missed at the tenth and twentieth fraction (Z =-0.55,P ＞ 0.05),respectively.In the meanwhile,11.45％ and 18.49％ of the normal tissues would be wrongly irradiated at the corresponding time points (Z =-2.49,P ＜ 0.05).Conclusions The variations of the spatial position of all targets were all less than 0.6 cm.The DI and the MI of the target decrease by various degrees during the treatment course,which lead to target mispositioning and normal tissue irradiation at different levels.

ObjectiveTo investigate the dosimetric difference in the application of RapidArc using 6 and 15 MV X-rays for radiotherapy of multiple hepatic malignancy.MethodsA total of 12 cases with multiple hepatic tumors ( primary 5 cases and secondary 7 cases) were selected.All patients underwent the three dimensional CT simulation in free breathing.For each patient,RapidArc plans with single or two 358° arcs using 6 or 15 MV X-rays were designed respectively,the prescription dose was 2Gy per fraction × 25 fractions.The dosimetric differences were compared among RapidArc plans.ResultsAll of RapidArc plans could meet the clinicalrequirement.There were no significant differences in the conformity index ( CI ),homogeneity index ( HI),the maximum dose and the minimum dose of PTV among RapidArc plans ( P ＞ 0.05).All the CI could get to 0.91 and HI could get to 0.88.In the RapidArc plans with two 358° arcs,the Vs,V10,V15 of normal liver were higher than with single arc,while V20,V25,V30,V35,V40 were lower than with single arc.There were no significant differences in the different radiation dose of normal liver,stomach,duodenum and spinal cord among different plans ( P ＞0.05 ).The monitor units of RapidArc plans using 6 MV X-rays increased 12％ compared to 15 MV averagely.CondusionThe 6 MV X-ray would be selected chiefly in the radiotherapy of multiple haptic tumor using RapidArc with whole arc(s).

Objective To compare the dosimetric difference of RapidArc and fixed gantry IMRT for liver carcinoma.Methods The CT data of 10 liver cancer patients were used to design 3 groups of treatment plan:IMRT plan,single arc RapidArc plan(RA1) ,and dual arc RapidArc plan(RA2).The planning target volume (PTV) dosimetric distrubition,the organs at risk (OAR) dose,the normal tissue dose,mornitor units(MU) and treatment time were compared.Results The maximum dose of PTV in RA1 and RA2 plans were lower than that of IMRT(Z = -2.090,-2.666,P ＜ 0.05).RapidArc groups had an improved 90% prescription dose conformity index than IMRT(Z = -2.805,-2.809 ,P ＜ 0.05).For organs at risk,RapidArc group plan had a significantly lower dose in V40 of stomach and small bowel than I MRT plan,but higher in mean dose of left kidney (Z = -1.988,-2.191,P ＜ 0.05).The values of V5,V10 and V15 of healthy tissue in RapidArc plan groups were higher than those in IMRT plan,while the values of V20 ,V25 and V30 of healthy tissue in RapidArc plan groups were lower than those in IMRT plan.The number of computed MU/fraction of Rapid Arc plan was 40% or 46% of IMRT plan and the treatment time was 30% and 40% of IMRT.Conclusion RapidArc showed improvements in conformity index and healthy tissue sparing with uncompromised target coverage.RapidArc could lead to the less MU and shorter delivery time compared to IMRT.