ABSTRACT
Objective To use the fusion image of the end-inhalation holding (EIH) phase and endexhalation holding (EEH) phase to define the target volume of individual patient with liver cancer,and to evaluate the target geometry,feasibility,and clinical significance of the technology.Methods Eighteen patients with liver caucer who were treated in our hospital from 2012 to 2013 were enrolled as subjects.With the same posture and scan range,all patients underwent contrast-enhanced three-dimensional computed tomography (3DCT) scans in the phases of free breathing (FB),EIH,and EEH.Gross tumor volume (GTV),clinical target volume (CTV),and organ of risk (OAR) were delineated on the above images.CTVFB was defined as GTV on the FB phase image (GTVFB) plus a margin of 10 mm,while planning target volume (PTVFB) was defined as CTVFB plus a margin of 10 mm in the right-left and anterior-posterior directions and a margin of 20 mm in the superior-inferior direction.GTVEI and GTVEE were defined as GTV on the EIH and EEH images,respectively.Based on the EEH images,the registered EEH and EIH images were fused to form GTVEI+EI.CTVEI+EE was defined as GTVEI+EI plus a margin of 10 mm,while PTVEI+EE was defined as CTVEI+EE plus a margin of 5 mm in the right-left and anterior-posterior directions and a margin of 10 mm in the superior-inferior direction.The Pinnacle3 v8.0m treatment planning system was used to design two 3D conformal radiotherapy plans for each patient.The volume,degree of inclusion (DI),matching index (MI),and central displacement of CTVFB and CTVEI+EE,as well as PTVFB and PTVEI+EE,were compared between the two plans.Results In the 18 patients,the mean CTVFB was significantly smaller than the mean CTVEI+EE(149.00±87.54 cm3 vs.188.17± 125.72 cm3,P=0.014);there was no significant difference between the mean PTVFB and PTVEI+EE (276.68± 146.41 cm3 vs.253.66± 117.35 cm3,P=0.080).DI of CTVFB to CTVEI+EF,PTVFB to PTVEI+EE,CTVEI+EE to CTVFB,and PTVEI+EE to PTVFB were (99.83±0.09)％,(84.55±8.45) ％,(80.83± 12.31) ％,and (99.78±0.08) ％,respectively.MI of CTVEI+EE to CTVFB and PTVEI+EE to PTVFB were 0.83± 0.07 and 0.87± 0.03,respectively.The central displacements of CTVEI+EE from CTVFB in x,y,and z axes were 0.55± 1.07 cm,0.76±3.02 cm,and-0.26± 1.98 cm,respectively (P =0.432,0.971,0.587).Conclusions In the treatment of liver cancer,the target volume delineation and image fusion using 3DCT images in EIH and EEH phases may avoid target omission due to respiratory movement,making it possible to increase radiation dose to target volume and improve the efficacy of radiotherapy.
ABSTRACT
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.
ABSTRACT
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.