Comparison of Tumor Volume Between 3D/4D CT and 3D/4D CBCT Under Respiratory Motion
Objective To evaluate the differences of internal target volume imaging between 3D/4D CT and 3D/4D CBCT in different motion modes,and to investigate the accuracy of various imaging methods in image-guided radiotherapy of lung stereotactic body radiation therapy under different motion modes.Methods A dynamic thorax phantom inserted with a mimic tumor with a diameter of 3 cm was programmed to simulate one-dimensional respiratory motion(period:4 s)in the superior-inferior direction.Four tumor motion patterns were simulated with functions of sin(x)and cos4(x),each with an amplitude of 10 mm and 5 mm,to achieve phantom images of 3D/4D CT and 3D/4D CBCT.All the 3D/4D CT images were obtained using Philips CT,all the 3D/4D CBCT images were collected using Elekta XVI Symmetry system.The volume of tumor inserted in the phantom were measured separately in the images of 3D CT,4D CT-average intensity projection(4D CT-AIP),4D CT-maximum intensity projection(4D CT-MIP),4D CT-ALL phases,and 3D CBCT,4D CBCT-AIP,4D CBCT-MIP,4D CBCT-ALL phases.Results The target volume of 3D CT was the smallest.In comparison,the volumes of 4D CT-ALL,4D CT-MIP,and 4D CBCT-MIP were similar.The Dice's similarity coefficient(DSC)between the ITV from 3D CT and ITV-ALL was the lowest,while that between the ITV from 3D CBCT and ITV-ALL was close.The DSC between the ITV(MIP-ALL)of 4D CT and 4D CBCT was the highest,and the DSC between the ITV(AIP-ALL)of 4D CT and 4D CBCT images was lower than that of ITV(MIP-ALL).Conclusion Quantitative information can be extracted from on-board treatment verification imaging(4D CBCT),and the combination of 4D CT and 4D CBCT could be an effective and alternative method for lung SBRT.
万方数据
维普
