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Purpose of the liver due to respiratory motion in three-dimensional displacement direction and lead to three-dimensional conformal radiation therapy (three dimensional conformal radiation therapy, 3DCRT) in liver enlargement or accuracy of the drop target. Application of four-dimensional CT (four dimensional computed tomography, 4DCT) techniques to determine primary liver cancer include breathing mobility of individualized target volume (within the target area), compared with conventional 3D 4D program planning target volume, displacement, normal liver tissue radiation dose and target dose distribution differences, evaluation techniques developed based on 4DCT radiotherapy planning and dosimetric advantage geometry to explore the technology used in the clinical significance of liver cancer radiotherapy. Methods 12 patients met the inclusion criteria of primary liver cancer patients each were performed Enhanced 3DCT and 4DCT scans and CT scans were obtained corresponding images. Which 4DCT image consists of 10 different respiratory phase of CT sequences. Images were sketched in 3DCT target solid tumors target (gross tumor volume, GTV), clinical target volume (clinical target volume, CTV), planning target volume (planning target volume, PTV) and the organs at risk; respectively in 4DCT images delineate tumor target IGTV, within the target (internal target volume, ITV) ITV, IPTV and organs at risk. GTV is 3DCT image tumor boundaries, IGTV as 4DCT images 10 different Respiratory Phase GTV overlay; GTV and CTV IGTV were expanded to 0.8cm and ITV; 3DCT the PTV to CTV plus conventional security perimeter (including respiratory move degree and setup errors), ie the direction of the left and right and front and both expansion 0.8cm, head and foot orientation are expanding 1.5 ~ 2cm; 4DCT's IPTV plans for the ITV plus boundary (position error) that are expanding 0.5cm. Application Xio treatment planning system designed sets for each patient radiotherapy treatment planning: 3D and 4D planning programs. Two sets of plans prescribed dose, radiation field are the same quantity and angle, and to ensure organs at risk does not exceed its tolerance dose. Comparing two sets of plans and IPTV PTV volume and dose distribution, GTV and IGTV displacement conditions and normal liver radiation dose differences. Results 12 patients PTV average volume of 249.54 ± 136.54cm ~ 3, IPTV, the average volume of 148.20 ± 92.02cm ~ 3, IPTV PTV volume reduction compared with 101.34 ± 63.87cm ~ 3, there was significant difference (P = 0.000) . With respect to the three-dimensional coordinates of the center IGTV, GTV in X, Y, Z-axis displacement were 0.23 ± 1.37cm, 0.05 ± 3.88cm, 0.12 ± 0.71cm, and moves to the left in the X-axis, Y axis cephalic move, Z dorsal axial movement, but the results were not statistically significant (P = 0.582,0.965,0.582). Compared with the 3D program, 4D planned dose distribution is more uniform, normal liver mean dose (mean dose to normal liver, MDTNL) decreased to 18.81 ± 3.89Gy the 14.59 ± 4.47Gy, V23 from the decreased to 34.78 ± 7.83% 26.18 ± 9.47%, V30 decreased by a 30.21 ± 7.30% to 22.95 ± 9.28%, normal liver tissue complication probability (normal tissue complication probability, NTCP) by the 12.72 ± 9.27% ??down to 6.46 ± 6.69%, the results were significantly different (P respectively 0.000,0.000,0.001). Conclusion Conventional 3DCT inaccurate positioning target phenomenon exists, and thus make it difficult precisely defined target volume 3DCRT, causing target range is too large or drop some targets, resulting in dose reduction target and normal liver tissue into excessive target. 4DCT technique can accurately record the track tumor movement with respiration, pinpoint target position, to avoid losing target; individualized determination of target volume, reducing the scope of foreign expansion, to avoid some unnecessary irradiation of normal liver tissue, in order to reduce the normal liver The NTCP, improved target dose thus improving liver cancer radiotherapy offer possible.
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