Comparison of gross tumor volume of primary oesophageal cancer based on contrast-enhanced three-dimensional, four-dimensional, and cone beam computed tomography

Background To explore motion information included in 3DCT, 4DCT and CBCT by comparing volumetric and positional differences of GTV. Results Independent of tumor location, significant differences were observed among volumes [IGTV10 > (IGTVCBCT or IGTVMIP) > (GTV3D or GTV4D50)]. The underestimations or overestimations between IGTV10 and IGTVCBCT were larger than those between IGTV10 and IGTVMIP (p < 0.001-0.011; p < 0.001-0.023). For upper oesophageal tumors, GTV4D50/IGTVCBCT negatively correlated with motion vector (r = -0.756, p = 0.011). In AP direction, the centroid coordinates of IGTVCBCT differed from GTV3D, GTV4D50, IGTVMIP and IGTV10 (p = 0.006, 0.013, 0.038, and 0.010). For middle oesophageal tumors, IGTV10/IGTVCBCT positively correlated with motion vector (r = 0.695, p = 0.006). The centroid coordinates of IGTVCBCT differed from those of IGTV10 (p = 0.046) in AP direction. For distal oesophageal tumors, the centroid coordinates of IGTVCBCT showed significant differences to those of IGTVMIP (p = 0.042) in LR direction. For both middle and distal tumors, the degrees of associations of IGTV10 outside IGTVCBCT significantly correlated with the motion vector (r = 0.540, p = 0.046; r = 0.678, p = 0.031). Materials and Methods Thirty-four oesophageal cancer patients underwent 3DCT, 4DCT and CBCT. GTV3D, GTV4D50, internal GTVMIP (IGTVMIP) and IGTVCBCT were delineated on 3DCT, 4DCT50, 4DCTMIP and CBCT. GTVs from 10 respiratory phases were combined to produce GTV10. Differences in volume, position for different targets, correlation between volume ratio and motion vector were evaluated. The motion vector was the spatial moving of the target centroid position. Conclusions IGTVCBCT encompasses more motion information than GTV3D and GTV4D50 for upper oesophageal tumors, but slightly less than IGTV10 for middle and distal oesophageal tumors. IGTVCBCT incorporated similar motion information to IGTVMIP. However, motion information encompassed in CBCT and MIP cannot replace each other.