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 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 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.

Objective To analyze artifacts of gross tumor volume (GTV) and correlated factors in each phase images of four dimensional CT (4DCT) for peripheral lung cancer based on three dimensional CT (3DCT) assisted with active breathing control.Methods Nineteen patients with peripheral lung cancer underwent 3DCT (CTFB) and 4DCT simulation scans during free breathing and then underwent 3DCT simulation scans in end inspiration hold (CTEIH) and end expiration hold (CTEEH) assisted with active breathing control.The relative deviations (Devref) between the reference GTV (GTVref) and the GTVsdelineated based on CTFB (GTVFB) and all phases of 4DCT were calculated respectively.Correlations between GTVref and Devmax and between the tumor motion in the cranio-caudal (CC) direction and Devref were analyzed.Results The maximum median Devref of GTV was GTVFB with 17.83％,and the maximum median Devref of the GTV in all phases of 4DCT was GTV30 with 17.20％.A significant negative correlation was found between GTVEIH and Devmax (r =-0.691,P =0.001).The Devref was crrnelated with the tumor motion amplitude in the CC direction (r =0.323-0.617,P =0.005-0.150).The partial regression coefficient of influence of GTVref size and motion amplitude in the CC direction to the tumor Devmax were -0.500 and 0.583,P =0.002 and 0.001,respectively.Conclusions The GTV artifacts in different phase of 4DCT for the peripheral lung cancer were different to each other,and the influence of target displacement to artifacts was larger than that of target volume,so artifacts could be reduced by controlling breathing to reduce target displacement.

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 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.

Objective To investigate the correlations of the whole breast displacement in different respiratory cycle during free breathing (FB) following breast-conserving surgery to the displacement of selected skin marker,nipple,and selected surgical clip based on four-dimensional computed tomography (4D-CT).Methods Thirteen breast cancer patients who had undergone breast-conserving surgery received whole breast intensity-modulated radiotherapy (IMRT).Respiration-synchronized 4D-CT image data were gathered during FB and were exported to the Varian Eclipse treatment planning system,and the whole breast target,nipple,superior clip,and metal marker on the skin at the anterior body midline were delineated on the CT images of ten phases of the respiratory cycle by the same radiotherapist based on the same delineating criteria.The displacement distances of the delineated target in the mediolateral (x),anteroposterior (y),and superoinferior (z) axles were achieved,and the correlations of the whole breast target displacement to the displacement of the clip,nipple,and skin marker were analyzed.The ipsilateral lung was delineated on the CT images of every phase of the respiratory cycle,and the changes in ipsilateral lung volume were analyzed during the respiratory cycle relative to the displacement of the breast.Results The maximal displacement distances of the whole breast target in the x,y,and z axles during FB were 0.71,0.76 and 1.29 mm,respectively ( F =5.755,P ＜ 0.05 ).There was no relationship between the three-dimensional (3D) displacement of the whole breast and the volume of the whole breast (r =-0.264,P ＜ 0.05 ),and there was no relationship between the displacemeat of the whole breast and the volume change of the ipsilateral lung ( r =0.346,P ＜ 0.05).There was no significant difference among the mean target displacement distances in 3 axles,and among 2 selected successive end-inspiration (EI) phases and 3 selected successive end-expiration (EE) phases.There was no significant difference between the volumes of the whole breast targets at the selected El and EE phases.There was no relationship between the displacement of the whole breast target and the displacement of the nipple,skin marker or superior clip in the cavity along the x- and z-axles.Along the y-axle,8/13,7/11 and 9/13 of the patients showed displacement of the whole breast target relative to the displacement of the nipple,skin marker and superior clip respectively.However,according to a population-based analysis,the displacement of the whole breast target was only significantly associated with the displacement of the superior clip ( r =0.657,P ＜ 0.05 ).Conclusions The clip registration is more credible and sensitive than a skin marker or the nipple for measuring and correcting the displacement of the whole breast target during radiotherapy.

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 compare the position,volume and matching index (MI) of patientspecific internal gross tumor volume (IGTV)delineated by 4 different approaches based on three- dimensional and four - dimensional CT ( 3 DCT and 4 DCT ) image for primary esophageal cancers.Methods Thirteen patients with primary esophageal cancer underwent 3DCT and 4DCT simulation scans during free breathing,and the patient were divided into group A (tumor located in the proximal thoracic esophagus) and B (tumor located in the mid-and distal thoracic esophagus).IGTV were delineated using four approaches: The gross tumor volume (GTV) contours from 10 respiratory phases were combined into IGTV10 ;IGTV2 was acquired by combining the GTV from 0％ and 50％ phases; IGTVMIP was the GTV contour delineated from the maximum intensity projection (MIP) ;IGTV3D was acquired from the enlargement of 3 DCT-based GTV by each spatial direction on the motion amplitude measured in the 4DCT.ResultsTarget movement in lateral (LR),anterio-posterior (AP),superio-inferior (SI) directions showed no statistically significant difference (0.11 cm,0.09 cm,0.18 cm,respectively; χ2 =1.06,P=0.589),and there was no statistically significant difference in centroid positions between IGTV10 and IGTV2 or IGTV3D in group A (t =-2.24,-0.00,P =0.089,- 1.000 ),MI between IGTV10 and IGTV2,IGTV10 and IGTV3D were 0.88,0.54,respectively. For group B, target movement amplitude in SI direction was bigger than in LR, AP ( 0.47 cm,0. 15cm,0. 12 cm,X2= 12.00,P = 0.002).Therewasno significantdifference betweenIGTV10 andIGTV3D inLR, AP, SI ( t =- 0.80.- 0.82,- 1.16,P = 0.450.0.438.0.285 ), MI was 0.59 ; but the target center coordinates was demonstrated significant difference in SI between IGTV10 and ICTV2 for group B ( t = 2.97.P = 0.021 ), Mlwas 0.86.Thevolume of IGTVMIPwassmaller thanIGTV10 ( t =- 2.84,P = 0.025 ), but the position of IGTv10 and ICTVMIp were with no statistically significant difference in the LR,AP,SI ( t =- 0.25,0. 84. - 1.22,P = 0. 809,0.429.0.263 ) ,MIbetweenIGTV10andIGTVMIp was 0.78.Conclusions Patient-specific IGTV can be acquired from 4DCT with correct target coverage while avoiding a geographic miss for the thoracic esophageal cancer,but IGTV2 and IGTVMIP can not contain all the information about primary tumor position,shape.and size at different phases of the respiratory cycle.