Feasibility of CBCT online registration by target areas in stereotactic body radiotherapy for lung cancer(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2019年第3期
- Page:
- 282-286
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Feasibility of CBCT online registration by target areas in stereotactic body radiotherapy for lung cancer
- Author(s):
- SUN Xiaohuan; TAN Li’na; WANG Zhongfei; XIAO Feng
- Department of Radiation Oncology, the First Affiliated Hospital of Air Force Medical University, Xi’an 710032, China
- Keywords:
- Keywords: lung cancer; stereotactic body radiotherapy; cone beam CT; shifting of target area; dose distribution; online registration
- PACS:
- R815
- DOI:
- DOI:10.3969/j.issn.1005-202X.2019.03.007
- Abstract:
- Abstract: Objective Positioning verification before cone beam CT (CBCT)-guided stereotactic body radiotherapy (SBRT) is of great importance. However, due to the respiratory motion, target areas were seriously deviated from planning image when using the bony structure or the skin marker to align the CBCT with planning CT, and the bony structure or the body outline would not match when using the image registration based on target areas. Herein the feasibility of CBCT online registration by target areas is discussed. Methods Nine patients receiving SBRT for lung were enrolled in this study. All the patients were scanned with 4DCT. Varian Eclipse 13.5 treatment planning system was used to design volumetric modulated arc therapy (VMAT) plans for each patient, with a prescribed dose of 60 Gy/10 F, and Varian iX accelerator was adopted in the treatment. The planning target volume (PTV) on original CT image was shifted to the right, feet and back by 0.5 or 1.0 cm, and according to the shifting of PTV, the isocenter of each plan was shifted by 0.5 or 1.0 cm. Subsequently, the dose distribution was recalculated to generate a PTV-shift plan. The differences in the dosimetric parameters of target areas and organs-at-risk between the original plan and PTV-shift plan were evaluated, so as to investigate the effects of PTV-shift on dose distribution. Results The maximum dose (Dmax), minimum dose (Dmin), mean dose (Dmean) and V60 of PTV in the original plan were 108.5%±1.6%, 98.3%±0.2%,101.1%±0.9%, 95.1%±0.3%, respectively (Dmax, Dmin, Dmean were represented by the percentage relative to target prescription dose). The Dmax of the spinal was (9.7±1.9) Gy, and the V20 and Dmean of lungs were 5.2%±1.9% and (3.9±1.4) Gy, respectively. Statistical differences between two plans were found in the Dmax of PTV after PTV was shifted by 1 cm in X direction, 0.5 or 1.0 cm in Y and Z directions, and in Dmin and V60 of PTV after PTV was shifted by 0.5 cm in Y direction, but the results still satisfied the requirements of RTOG report 0915. Moreover, statistical differences were also found in the dose of spinal cord after PTV was shifted by 0.5 or 1.0 cm in Z direction, and in the V20 and Dmean of lungs after PTV was shifted by 0.5 or 1.0 cm in Y direction, but the results still satisfied the requirements of RTOG report 0915. Conclusion For patients receiving SBRT for lung cancer, the image registration based on target areas is recommended in CBCT online registration. Repositioning is not necessary if the setup error was small than 1 cm, and therapy can be initiated after adjusting the treatment couch.
Last Update: 2019-03-25