Objective To explore the influence of different reconstruction modes with time?weighted respiratory phases on the internal tumor volume ( ITV) of solitary pulmonary lesion ( SPL) , and to evaluate the feasibilities of 8 and 4 equal time?weighted respiratory phases in 4DCT simulation. Methods 24 patients with SPL underwent 4D scanning. Images were reconstructed with 10, 8 and 4 equal time?weighted phases of the respiratory cycles, respectively. Gross tumor volumes ( GTVs ) were delineated on the three sets of reconstructed images and fused into ITVs, which were ITV10 , ITV8 and ITV4 respectively. The differences of volumes, centroid of the ITVs and motions of GTV centroids in three?dimensional directions were compared. Statistical analysis was performed using the Friedman M test. Results The volumes of ITV10 , ITV8 and ITV4 were (9.09±12?29) cm3,(9.10±12?47) cm3 and (8.98±12?61) cm3(P=0?001), respectively. There were no differences between the volumes of ITV10 and ITV8 after the Bonferroni correction ( P=0?721) , while the opposite between those of ITV10 and ITV4 ( P=0?002 ) . The differences of centroid positions of ITV10, ITV8 and ITV4 in x?, y?and z?axes were all less than 1 mm ((12.22±7?71),(12.23± 7?71),(12.22±7?71),Px =0?668);(43.30±29?38),(43.30±29?40),(43.31±29?39),Py =0?643;(5.66±3?67),(5.66±3?67),(5.66±3?67),Pz=0?878), similar to the motions of GTV centroids in three reconstructed modes ((0.69±0?56),(0.69±0?68),(0.79±0?51) mm,Px=0?356;(3.13±3?78),(3.13± 4?05),(3.19±4?06) mm,Py =0?978;(1.18±1?31),(1.03±1?32),(1.16±1?34) mm,Pz=0?302). Conclusions There were no differences in volumes, centroid positions and motions between ITV10 and ITV8 . The quantity of reconstruction images and GTV delineations according to 8 time?weighted phases were both less than conventional 10 phases. 8 time?weighted respiratory phases mode was feasible in 4DCT simulation for SPL.

Objective To investigate the impact of movement frequency on gross tumor volume (GTV) of moving tumors and coordinate position of the central point based on three-and four-dimensional CT scans.Methods The respiratory motion platform from Modus and 8 phantoms with different shapes and volumes were used to simulate the movement of lung tumors.Three-and four-dimensional CT scans were performed at movement frequencies of 10,15,and 20 times/min.GTV (GTV10,GTV15,and GTV20) and IGTV (IGTV10,IGTV15,and IGTV20) were delineated,and the coordinate position of the central point was obtained.The Friedman test was performed for GTV10,GTV15,GTV20,IGTV10,IGTV15,IGTV20,and the coordinate position of the central point.Results GTV10,GTV15,and GTV20 at the three movement frequencies were 12.41±14.26 cm3,10.38±11.18 cm3,and 12.50±15.23 cm3,respectively (P=0.687),and the positional values were-8.2±96.2 mm,-8.6±96.1 mm,and-8.6±95.7 mm in x-axis (P=0.968),108.2±25.0 mm,110.4±22.5 mm,and 109.0±24.2 mm in y-axis (P=0.028),and 65.2±13.7 mm,65.4± 13.4 mm,and 65.4± 13.2 mm in z-axis (P =0.902).IGTV10,IGTV15,and IGTV20 at the three movement frequencies were 17.78± 19.42 cm3,17.43± 19.56 cm3,and 17.44± 18.80 cm3,respectively (P=0.417),and the positional values were-7.7±95.9 mm,-7.9±95.6 mm,and-7.9±95.1 mm in x-axis (P=0.325),109.4±24.5 mm,109.6±24.1 mm,and 109.2±24.3 mm in y-axis (P=0.525),and 65.5±13.3 mm,65.6±13.4 mm,and 65.5±13.3 mm in z-axis (P=0.093).Conclusions During simulated positioning of thoracic tumors,respiratory movement frequency has no significant impact on target volume established by four-dimensional CT scan.There are no significant differences in three-dimensional target volume established at different respiratory frequencies,but respiratory frequency has a significant impact on the position of the central point of the target volume in y-axis.

Objective To compare volumetric size, conformity index (CI), degree of inclusion (DI) of internal gross target volumes (IGTV) delineated on 4D-CT-MIP and PET-CT images for primary thoracic esophageal cancer. Methods Fifteen patients with thoracic esophageal cancer sequentially underwent enhanced 3D-CT, 4D-CT and PET-CT simulation scans. IGTVMIP was obtained by contouring on 4D-CT maximum intensity projection ( MIP). The PET contours were determined with nine different threshold methods (SUV≥2?0, 2?5, 3?0, 3?5), the percentages of the SUVmax(≥20%, 25%, 30%, 35%, 40%) and manual contours. The differences in size, conformity index (CI), degree of inclusion ( DI) of different volumes were compared. Results The volume ratios ( VRs) of IGTVPET2. 5 to IGTVMIP , IGTVPET20% to IGTVMIP, IGTVPETMAN to IGTVMIP were 0?86, 0?88, 1?06, respectively, which approached closest to 1. The CIs of IGTVPET2?0,IGTVPET2.5,IGTVPET20%,IGTVPETMAN and IGTVMIP which were 0?55, 0?56, 0?56, 0?54,0?55, respectively, were significantly larger than other CIs of IGTVPET and IGTVMIP (Z= -3?408-2?215,P <0?05). There were no statistical significance in the DIs of IGTVMIP and IGTVPET2.5,IGTVMIP and IGTVPET20%, IGTVMIP and IGTVPETMAN(0?77,0?82,0?71,0?67, 0?68,0?82,P>0?05). Conclusions The targets delineated based on SUV threshold setting of≥2?5, 20% of the SUVmax and manual contours on PET images correspond better with the target delineated on maximum intensity projection of 4D-CT images than other SUV thresholding methods.

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.

Objective To study the feasibility of defining the internal gross tumor volume (IGTV) of hepatocellular carcinoma applying the enhanced four-dimensional computed tomography (4DCT) images with deformable registration technology.Methods Ten HCC patients who accepted radiation therapy were selected in this study.The 4DCT in free breathing,non-enhanced 3DCT and arterial phase enhanced 3DCT in end inspiration breath holding associated with active breathing coordinator were acquired sequentially.4DCT were sorted into ten series CT images according to breath phase,and named CT00,CT10..…CT90.Gross tumor volume (GTV) were contoured on different CT series and the IGTV1 was merged by ten phases GTVs of 4DCT.The GTV of enhanced 3DCT was registered to different CT series of 4DCT and the IGTVDR was obtained by merging the GTVs after deformable registration.The target volumes differences were compared by paired t-test.Results The edge of tumor was difficult to define on 4DCT and non-enhanced 3DCT images.The enhanced 3DCT image showed clearer tumor edge,and the GTV increased by mean 37.99％ compared to GTV on 4DCT different series images and non-enhanced 3DCT image (P =0.002).The GTV after deformable registration on 4DCT different phase images increased by mean 36.34％ (P =0.011),which were similar to GTV on enhanced 3DCT image (P =0.632).The IGTVDR increased by 19.91％ (P =0.017),compared to IGTV1.Conclusions The contrast-enhanced 4DCT image which was obtained by combining enhanced 3DCT and 4DCT images with deformable registration technology could raise the position precision of the HCC IGTV effectively.

Objective To investigate the variations of the spatial position and overlap ratio for gross tumor volume (respiratory phase 50％) (GTV50) and internal gross tumor volume (IGTV) of primary thoracic esophageal cancer during conventional fractionated radiotherapy based on repeated four-dimensional computed tomography (4DCT) scans.Methods Thirty-three patients with thoracic esophageal cancer underwent contrast-enhanced 4DCT scans before radiotherapy and at the 10th and 20th fractions of radiotherapy.Scans were registered to the baseline 4DCT scan using bony landmarks.The GTV50 was delineated by the same radiotherapist on each 4DCT imaging data set,and the IGTV was constructed accordingly.The target volume,degree of inclusion (DI),and matching index (MI) were compared in different phases.Results The volumes of GTV50 and IGTV decreased along with treatment course.No significant changes in the centroid position were observed for the GTV50 and IGTV.The median DIs of the target volumes at the 10th and 20th fractions in the original target volume were 0.75 and 0.63(P =0.000) for GTV50 and were 0.79 and 0.66(P=0.000) for IGTV,while the median MIs were 0.61 and 0.56(P=0.002) for GTV50 and were 0.68 and 0.58 (P =0.005) for IGTV.A positive correlation between the variation of volume ratio and the variation of DI was found for GTV50 and IGTV (r =0.632,r =0.783),and the variation of volume ratio was also positively correlated with the variation of MI (r =0.387,r =0.483) ;the 3D vector was negatively correlated with the MI (r =-0.455,r =-0.438).Conclusions During conventional fractionated radiotherapy,the variation of spatial position is less than 0.8 cm for GTV50 and IGTV of primary thoracic esophageal cancer,and the decline of the target leads to varying degrees of decreases in DI and the MI.

Objective To compare and analyze the dosimetric characteristics of the intensity-modulated arc therapy (RapidArc) combined with active breathing coordinator (ABC) in the thoracic esophageal carcinoma radiation therapy. Methods Ten thoracic esophageal carcinoma patients undergoing radiotherapy were selected for this study.The CT simulations were performed under three breath patterns respectively:moderate deep inspiration breath-hold (mDIBH) with ABC aid; Set the trigger threshold to 80％ of the peak of the respiration curve; and free breathing (FB).Based on the corresponding CT image sets,three treatment plans were generated for each patient respectively:Arc-ABC( three small arcs),ArcFB (consisted of two coplanar full arcs) and IMRT-FB plan.The following dosimetric parameters were compared among different plans:D2％,D98％,V95,homogeneity index ( HI),conformal index ( CI ) the percentage of volume receiving dose of over x Gy (Vx),monitor unit (MU),control points and treatment time.Results The planning target volume ( PTV ) of FB was 376 cm3 which decreased to 260 cm3 after using ABC.For mDIBH and FB patients,the total lung volumes were 5964.6 cm3(35％ more than FB) and 3838.8 cm3 respectively; the heart volumes were 524.4 cm3 and 642.7 cm3 respectively. No significant difference was observed among Arc-ABC,IMRT-FB and Arc-FB in terms of D2,D98,V95,CI and HI.For Arc-ABC plans,there were significant decreases of radiation dose in total-lung's V10,V20,V30,V40 and mean lung dose ( F =4.38,5.34,4.07,3.89,4.28,P ＜0.05).Various dose decreases of heart V20,V3,V40,Dmean and spinal cord Dmax were observed,yet no statistically significant difference existed.The MUs and total control points of Arc-ABC plans were significantly lower than other plans ( F =26.86,12.56,P ＜ 0.05 ).Conclusions When thoracic esophageal carcinoma patients were treated with radiotherapy,the combined utilization of RapidArc and ABC can potentially decrease the volume of irradiated lung yet escalate the dose in target.

ObjectiveTo explore the influence of the CT scanning mode on the gross tumor volume (GTV) delineation of solitary pulmonary lesion (SPL),and to evaluate the feasibility of the spiral CT scan in CT simulation.Methods Sixteen patients with SPL underwent axial scan,spiral scan during free breathing.Compare the target position,volume between GTVS and GTVA (paired t-test).The matching index (MI) between GTVS and GTVA and correlations between MI and the tumor volume were calculated ( bivariate correlation analysis).ResultsGTVS and GTVA volume was 8.95 cm3 and 9.38 cm3 ( t =0.43,P =0.667),respectively.The centroid position for GTVS and GTVA in x,y and z axises were 6.80 cm and 6.81 cm (t =0.27,P =0.794),36.19 cm and 36.05 cm (t =0.37,P =0.717),and 4.99 cm and 4.96cm (t =0.65,P =0.526),respectively.There were also no statistically significant difference in the distance between the centroidal position and origin of coordinates for GTVS and GTVA (38.31 cm∶ 38.23 cm,t =0.47,P =0.646 ).MI between GTVS and GTVA was 0.36 ( range 0-0.77 ),correlated with the tumor volume (r =0.587,P =0.017).ConclusionsThere was no significant difference between the axial scan and spiral scan in the GTV volume and position for SPL,but MI between GTVS and GTVA were small.A correlation was found for the MI between GTVS and GTVA with the tumor volume.Spiral CT scan was more timesaving,and was feasible in CT simulation scan.

ObjectiveTo measure the displacement of solitary pulmonary lesion (SPL) using fourdimensional CT (4DCT), and to compare the planning target volume using 4D maximum intensity projection (MIPMIP) ( PTV4DMIP ) with the empirical PTV3D.Methods Data were acquired from 24 consecutive patients with SPL. For each patient, respiration-synchronized 4DCT images and standard axial CT scans were obtained during free breathing.In lung window setting,the 4D technique was used to measure the displacement of SPL in three dimensions. We compared an PTV created using the MIP (PTV4DMIP) to the PTV created from the gross tumor volume (GTV) enlarged isotropically for each spatial direction by 1.0 cm and 1. 5 cm in the PTV3D1.0cm and PTV3D1.5cm. Results The SPL located in the lower lobe showed significant difference with the upper and middle lobe in y axis (0. 44 cm,0. 92 cm, t =2. 87, P =0. 000),but there was no difference in both x and z axis (0. 27 cm,0. 39 cm,t =1.44 ,P =0. 116 and 0. 29 cm,0. 40 cm,t =1.51, P =0. 227). SPL showed significantly greater displacement in y axis than in both x and z axis [0.60 cm and0. 31 cm (t =4.23,P=0.000) ,0.60 cm and 0.32 cm (t =4.65,P=0. 000)], but there was no significant difference between x and z axis (0. 31 cm,0. 32 cm,t =0. 33 ,P =0. 741 ). There was no statistically difference between the peripheral lung cancer and the pulmonary metastasis tumor in three directions ( x axis : 0. 37 cm,0. 32 cm, t =0. 52, P =0. 223 ; y axis : 0. 54 cm, 0. 95 cm, t =- 1.38, P =0.061;z axis:0.42 cm,0.37 cm, t=0.29, P=0.859).Both PTV3D1.0cm and PTV3D1.5cm showed significantly greater volume than PTV4DMIP(46. 73 cm3 ,86. 52 cm3 and 30. 02 cm3 ,t =- 11.35, - 12. 09,P =0. 000,0. 000). ConclusionsThe displacement of SPL in y axis is much greater than x and z axis. The empirical PTV3D is much bigger than PTV4DMIP, which suggests that 4DMIP provide adequate coverage of the moving target and minimize dose to normal tissues.

Objective To research the feasibility of using three-dimensional CT (3DCT) associated with active breathing control (ABC) in determination of the individual internal tumor volume (ITV) for hepatocellular carcinoma (HCC) comparing the four-dimensional CT (4DCT).Methods After 4DCT scans of 15 HCC patients who had accepted TACE,completed the 3DCT scans associated with ABC in three ways of breathing:free breathing ( FB),end inspiration hold ( EIH),end expiration hold (EEH).4DCT images were sorted into 10 phases and the maximum intensity projection (MIP) images were constructed.The GTVs were manually contoured on 4DCT and 3DCT images (labeled as GTV0,GTV10.….GTV90,GTVMIP,,GTVFB,GTVEIH and GTVEEH).GTV0…GTV90,GTV0 and GTV50,GTV0,GTV20 and GTV50,GTVEIH and GTVEEH were respectively merged into IGTV1,IGTV2,IGTV3,IGTV4.The volume and geometry displacement of GTVs and IGTVs were compared.Results All patients were compatible with the ABC technique and completed the CT scans in two ways.The motion of diaphragm measured between 4DCT and 3DCT images was not significantly different ( 1.39 cm and 1.39 cm,t =-0.02,P =0.983 ),it was similar to the volume difference among GTV0,GTV20,GTV50,GTVEIH,GTVEEH and GTVFB (56.4,54.6,55.5,55.6,55.2,59.7 cm3,F =0.01,P =1.000 ).The comparison result of volume difference among IGTV1,IGTV2,IGTV3,IGTV4 and GTVMIP (77.9,71.4,73.4,72.3 and 66.3 cm3,F =0.02,P =1.000)were similar to the differences of geometry displacement in x,y and z axial among them (F =0.48,0.04,0.02,P =0.750,0.997,0.999,respectively).Conclusion The application of 3DCT associated with ABC in determination of the individual IGTV for HCC is feasible and safe comparing to 4DCT.