ABSTRACT
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.
ABSTRACT
Objective To compare positional and volumetric differences of internal gross tumor volume (IGTV) delineated separately by three approaches based on four-dimensional CT (4DCT) for the primary tumor of non-small cell lung cancer (NLCLC). Methods Twenty-one patients with NLCLC underwent big bore 4DCT simulation scan of the thorax. IGTVs of the primary tumor of NSCLC were tumor on the MIP images were delineated to produce IGTVMIP. The position of the target center, the volume of target, the degree of inclusion (DI) and the matching index (MI) were compared reciprocally between IGTV10, IGTVEI+EE and IGTVMIP. Results Average differences between the position of the center of IGTVs on direction of x,y and z axes were less than 1 mm, with no statistically significant difference. The volume of IGTV10 was larger than that of IGTVEI+EE, the difference was statistically significant (t=2.37,P=0.028);the volume of IGTV10 was larger than that of IGTVMIP, but the difference was not statistically significant(t=1.95 ,P=0.065). The ratio of IGTVEI+EE with IGTV10, IGTVMIP with IGTV10 were 0.85±0.08 and 0.92±0.11, respectively. DI of IGTVEI+EE in IGTV10, IGTVMIP in IGTV10 were 84.78% ± 8. 95% and 88.47% ±9.04%. MI between IGTV10 and IGTVEI+EE, IGTV10 and IGTVMIP were 0.85 ±0.09, 0.86±0. 09, respectively. Conclusions The center displacement of the IGTVs delineated separately by the three different techniques based on 4DCT images are not obvious; IGTVEI+EE and IGTVMIP can not replace IGTV10 , however , IGTVMIP is more close to IGTV10 comparing to IGTVEI+EE . The ratio of GTVEI+EE with IGTV10 is correlated to the tumor motion vector. As the vector increases, the ratio of GTVEI+EE with IGTV10decreases, especially for small tumors.