Abstract
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 [IGTV(10) > (IGTV(CBCT) or IGTV(MIP)) > (GTV(3D) or GTV(4D50))]. The underestimations or overestimations between IGTV(10) and IGTV(CBCT) were larger than those between IGTV(10) and IGTV(MIP) (p < 0.001-0.011; p < 0.001-0.023). For upper oesophageal tumors, GTV(4D50)/IGTV(CBCT) negatively correlated with motion vector (r = -0.756, p = 0.011). In AP direction, the centroid coordinates of IGTV(CBCT) differed from GTV(3D), GTV(4D50), IGTV(MIP) and IGTV(10) (p = 0.006, 0.013, 0.038, and 0.010). For middle oesophageal tumors, IGTV(10)/IGTV(CBCT) positively correlated with motion vector (r = 0.695, p = 0.006). The centroid coordinates of IGTV(CBCT) differed from those of IGTV(10) (p = 0.046) in AP direction. For distal oesophageal tumors, the centroid coordinates of IGTV(CBCT) showed significant differences to those of IGTV(MIP) (p = 0.042) in LR direction. For both middle and distal tumors, the degrees of associations of IGTV(10) outside IGTV(CBCT) 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. GTV(3D), GTV(4D50), internal GTV(MIP) (IGTV(MIP)) and IGTV(CBCT) were delineated on 3DCT, 4DCT(50), 4DCT(MIP) and CBCT. GTVs from 10 respiratory phases were combined to produce GTV(10). 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: IGTV(CBCT) encompasses more motion information than GTV(3D) and GTV(4D50) for upper oesophageal tumors, but slightly less than IGTV(10) for middle and distal oesophageal tumors. IGTV(CBCT) incorporated similar motion information to IGTV(MIP). However, motion information encompassed in CBCT and MIP cannot replace each other.