Abstract：Objective To determine the positional and volumetric differences between the target volumes delineated based on three-dimensional computed tomography (3DCT), four-dimensional computed tomography (4DCT), and cone-beam computed tomography (CBCT) in non-small cell lung cancer (NSCLC). Methods Thirty-one patients with peripheral NSCLC sequentially underwent 3DCT and 4DCT simulation scans of the thorax during normal breathing. A 3D conformal treatment plan was created based on 3DCT. Before the first treatment, CBCT was performed and registered to the planning CT using bony anatomy registration. All contours were delineated by a radiation oncologist using the same contouring protocol. GTV3D and GTV4D50% were contoured based on 3DCT and end-expiration phase (50% phase) of 4DCT, respectively;internal GTVs (IGTVMIP and IGTVCBCT) were contoured based on maximum intensity projection (MIP) of 4DCT and CBCT, respectively. The differences in the position, size, and degree of inclusion (DI) between these volumes were determined by Wilcoxon rank-sum test and paired t-test. The Pearson test was used for the correlation analysis on 3D motion vector of GTV. Results The mean size ratio of GTV3D, GTV4D50%, and IGTVMIP to IGTVCBCT were 0.77, 0.84, and 1.10(z=－2.91, P=0.004;z=－2.79, P=0.005;z=－1.81, P=0.070) for tumors in the upper lobe of the lung and 0.67, 0.65, and1.17(z=－3.30, P=0.001;z=－3.30, P=0.001;z=－2.32, P=0.020) for tumors in the middle/lower lobe of the lung. GTV4D50%/IGTVCBCT ratio was negatively correlated with the 3D motion vector of GTV (r=－0.45, P=0.012) in all the patients. The mean DIs of GTV3D, GTV4D50%, and IGTVMIP in IGTVCBCT were 0.65, 0.65, and 0.62, respectively, and the DI of GTV3D or GTV4D50% in IGTVCBCT showed no significant difference from that of IGTVMIP in IGTVCBCT (t=－0.90, P=0.375;t=－1.42, P=0.167);the mean DIs of IGTVCBCT in GTV3D, GTV4D50%, and IGTVMIP were 0.47, 0.49, and 0.67, respectively, and the DI of IGTVCBCT in IGTVMIP was significantly greater than that of IGTVCBCT in GTV3D or GTV4D50%(t=－8.28, P=0.000;t=－5.70, P=0.000). Conclusions CBCT can help to acquire significantly more information on tumor motion than 3DCT and end-expiration phase of 4DCT, but with slightly less information than 4DCT MIP. The use of 3DCT or 4DCT registered to CBCT based on bony anatomy may still result in a serious target miss in radiotherapy, which should be focused on when we perform adaptive radiotherapy and rectify treatment planning based on CBCT.
LI Feng-xiang,LI Jian-bin,SHAO Qian et al. A comparative study of target volumes based on three CT images in non-small cell lung cancer[J]. Chinese Journal of Radiation Oncology, 2013, 22(4): 286-290.
[1] Underberg RWM, Lagerwaard FJ, Slotman BJ, et al. Use of maximum intensity projections (MIP) for target volume generation in 4DCT scans for lung cancer. Int J Radiat Oncol Biol Phys,2005,63:253-260. [2] Li FX, Li JB, Zhang YJ et al. Comparison of the planning target volume based on three-dimensional CT and four-dimensional CT images of non-small-cell lung cancer. Radiother Oncol,2011,99:176-180. [3] 李奉祥,李建彬,张英杰,等.四维影像在肿瘤放射治疗中的应用.中华肿瘤杂志,2011,33:721-725. [4] Wang Z, Wu J, Marks LB, et al. Cone-beam CT localization of internal target volumes for stereotactic body radiotherapy of lung lesions. Int J Radiat Oncol Biol Phys,2007,69:1618-1624. [5] 王利宁,李建彬,徐敏,等.勾画者及勾画标准对基于4DCT周围型肺癌靶区勾画的影响.中华放射医学与防护杂志,2012,32:494-497. [6] Galerani AP, Grills I, Hugo G, et al. Dosimetric impact of online correction via cone-beam CT-based image guidance for stereotactic lung radiotherapy. Int J Radiat Oncol Biol Phys,2010,78:1571-1578. [7] Hof H, Rhern B, Haering P, et al. 4D-CT-based target volume definition in stereotactic radiotherapy of lung tumors:comparison with a conventional technique using individual margins. Radiother Oncol,2009,93:419-423. [8] Wulf J, Hadinger U, Oppitz U, et al. Stereotactic radiotherapy of extracranial targets:CT-simulation and accuracy of treatment in the stereotactic body frame. Radiother Oncol,2000,57:225-236. [9] Guckenberger M, Meyer J, Wilbert J, et al. Cone-beam CT based image-guidance for extracranial stereotactic radiotherapy of intrapulmonary tumors. Acta Oncol,2006,45:897-906. [10] Yeung AR, Li JG, Shi W. Tumor localization using cone-beam CT reduces setup margins in conventionally fractionated radiotherapy for lung tumors. Int J Radiat Oncol Biol Phys,2009,74:1100-1107. [11] George R, Chung TD, Vedam SS, et al. Audio-visual biofeedback for respiratorygated radiotherapy:impact of audio instruction and audio-visual biofeedback on respiratory-gated radiotherapy. Int J Radiat Oncol Biol Phys,2006,65:924-933. [12] Persson GF, Nygaard DE, Munck Af Rosenschld P, et al. Artifacts in conventional computed tomography (CT) and free breathing four-dimensional CT induce uncertainty in gross tumor volume determination. Int J Radiat Oncol Biol Phys,2011,80:1573-1580. [13] Haasbeek CJ, Spoelstra FO, Lagerwaard FJ, et al. Impact of audio-coaching on the position of lung tumors. Int J Radiat Oncol Biol Phys,2008,71:1118-1123.
2013, Vol. 22 
