| LI Hong-sheng,LI Bao-sheng,SUN Tao,YIN Yong,LI Xu,YU Ning-sha.Study of image-guided radiotherapy for head and neck cancer based on on-line and off-line CBCT setup verification[J].Chinese Journal of Radiological Medicine and Protection,2009,29(3):280-282 |
| Study of image-guided radiotherapy for head and neck cancer based on on-line and off-line CBCT setup verification |
| Received:May 03, 2008 |
| DOI：10.3760/cma.j.issn.0254-5098.2009.03.010 |
| KeyWords:Head and neck cancer Planning target volume Adaptive radiotherapy Image-guided radiotherapy Cone-beam CT |
| FundProject:国家自然科学基金(30670617) |
| Author Name | Affiliation | | LI Hong-sheng | Department of Radiation Oncology, Shandong Tumor Hospital, Jinan 250117, China | | LI Bao-sheng | Department of Radiation Oncology, Shandong Tumor Hospital, Jinan 250117, China | | SUN Tao | Department of Radiation Oncology, Shandong Tumor Hospital, Jinan 250117, China | | YIN Yong | Department of Radiation Oncology, Shandong Tumor Hospital, Jinan 250117, China | | LI Xu | Department of Radiation Oncology, Shandong Tumor Hospital, Jinan 250117, China | | YU Ning-sha | Department of Radiation Oncology, Shandong Tumor Hospital, Jinan 250117, China |
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| Abstract:: |
| Objective To investigate how much the patient setup accuracy for irradiation of head and neck cancer can be improved by online setup verification and offline setup verification using cone-beam computed tomography(CBCT),and the feasibility of image-guided adaptive correction procedure to reduce the PTV margin.Methods 16 patients of head-and-neck cancer treated with three-dimensional conformal radiotherapy (3D-CRT)or intensity modulated radiotherapy(IMRT)were investigated. The first online kV CBCT scan, rigid image registration,setup correction were performed before radiotherapy. The second kV CBCT scan were acquired immediately after treatment and analysis was performed as above. CBCT scans were acquired at two or three fractions weekly during the entire course of radiotherapy and CBCT online-guided correction data were recorded. The data was used to calculate the population-based CTV-PTV margins under the condition of non-correction, correction every fraction and compensation of the systematic setup error respectively.The number of initial images required to predict systematic setup error was evaluated with the permission of 0.5 mm residue error.ResultsTotal of 320 sets of CBCT images were analyzed for 16 patients. Under the condition of non-correction,the margins required to account for total error are 5.7 mm,5.6 mm,and 7.3 mm in the left-right(X axis),cranio-caudal(Y axis),and anterior-posterior(Z axis)directions respectively. when the tumor was corrected every fraction, the margins required to account for intrafraction error are 1.7 mm,1.7 mm,and 2.3 mm in X, Y,and Z axis.To correct the systematic setup error,8 sets of CBCT images are adequate. After compensation for the effect of the systematic setup error, 2.7 mm,2.5 mm,and 3.6 mm PTV margins are necessary in X, Y,and Z axis respectively.Conclusions There exists some extent of setup error in head and neck 3D-CRT or IMRT.The on-line CBCT correction and the approach based on off-line adaptive correction both can be used to reduce the impact of setup error obviously, the required margins for the PTV was reduced accordingly. |
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