Open AccessAnalysis of the advantage of individual PTVs defined on axial 3D CT and 4D CT images for liver cancer
Author(s) -
Li Fengxiang,
Li Jianbin,
Xing Jun,
Zhang Yingjie,
Fan Tingyong,
Xu Min,
Shang Dongping,
Liu Tonghai,
Song Jinlong
Publication year - 2012
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1120/jacmp.v13i6.4017
Subject(s) - liver cancer , computed tomography , cancer , nuclear medicine , medicine , radiology , mathematics
The purpose of this study was to compare positional and volumetric differences of planning target volumes (PTVs) defined on axial three dimensional CT (3D CT) and four dimensional CT (4D CT) for liver cancer. Fourteen patients with liver cancer underwent 3D CT and 4D CT simulation scans during free breathing. The tumor motion was measured by 4D CT. Three internal target volumes (ITVs) were produced based on the clinical target volume from 3DCT (CTV 3 D): i) A conventional ITV (ITV conv) was produced by adding 10 mm in CC direction and 5 mm in LR and and AP directions toCTV 3 D; ii) A specific ITV (ITV spec) was created using a specific margin in transaxial direction; iii)ITV vectorwas produced by adding an isotropic margin derived from the individual tumor motion vector.ITV 4 Dwas defined on the fusion of CTVs on all phases of 4D CT. PTVs were generated by adding a 5 mm setup margin to ITVs. The average centroid shifts between PTVs derived from 3DCT andPTV 4 Din left–right (LR), anterior–posterior (AP), and cranial–caudal (CC) directions were close to zero. ComparingPTV 4 DtoPTV conv,PTV spec, andPTV vectorresulted in a decrease in volume size by 33.18% ± 12.39 % , 24.95% ± 13.01 % , 48.08% ± 15.32 % , respectively. The mean degree of inclusions (DI) ofPTV 4 DinPTV conv, andPTV 4 DinPTV spec, andPTV 4 DinPTV vectorwas 0.98, 0.97, and 0.99, which showed no significant correlation to tumor motion vector ( r = ‐ 0.470 , 0.259, and 0.244; p = 0.090 , 0.371, and 0.401). The mean DIs ofPTV convinPTV 4 D,PTV specinPTV 4 D, andPTV vectorinPTV 4 Dwas 0.66, 0.73, and 0.52. The size of individual PTV from 4D CT is significantly less than that of PTVs from 3DCT. The position of targets derived from axial 3DCT images scatters around the center of 4D targets randomly. Compared to conventional PTV, the use of 3D CT‐based PTVs with individual margins cannot significantly reduce normal tissues being unnecessarily irradiated, but may contribute to reducing the risk of missing targets for tumors with large motion. PACS number: 87