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Abstract
Purpose
We propose the measurement method of tumor movement for respiratory gated therapy in lung cancer patient for stereotactic radiosurgery, contouring method of tumor for radiation treatment planning using measured tumor movement. And through phantom study, we ascertain that the tumor movement is properly reflected in determination of PTV, and the tumor is properly and safely treated in full respiration phases and respiratory gated therapy.
Materials and Methods
Lung cancer phantom and 1-dimensional moving phantom were made to evaluate respiratory gated radiation therapy for lung SRS. 4D CT scan was performed using these phantoms and 10 sets of CT images and post-processed MIP (Maximum Intensity Projection) images were used to measure the tumor movement. The measured tumor movement in 4D CT images and MIP images were compared. Also, during radiation exposure in full respiration phases and respiratory gated phases, tumor movement included in radiation exposure was measured using EPID image and compared with measured data in 4D CT images and MIP images.
Results
The tumor movement measured in full respiration phases was 28.8mm and 29.1 mm in 4D CT images and MIP images respectively, and in respiratory gated phases, 30∼70% phases, was 12 mm and 12.2 mm respectively. The tumor contoured in each phase images and MIP images was well agreed in full respiration phases and respiratory gated phases. The tumor movement included in radiation exposure was 29.3 mm and 8.4 mm in full respiration phases and respiratory gated phases respectively.
Conclusion
The tumor movement measured in 4D CT images and MIP images was well agreed, so we propose to use of MIP image for contouring of tumor in full respiration phases and respiratory gated phases. In full respiration radiation treatment and respiratory gated radiation therapy, the tumor movement included in radiation exposure was well agreed with measured tumor movement in 4D CT images or MIP images, so we ascertain though this phantom study we can exactly treat the tumor including tumor movement. In respiratory gated radiation therapy, the tumor movement included in radiation exposure was about 30% smaller than measured tumor movement in 4D CT images or MIP images, so we ascertain that we can safely treat the tumor including tumor movement in current provided technique.
References
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Fig. 2.
CT image of manufactured lung cancer phantom. It was seen that CT density of the tumor is larger than surrounding tissue.
Fig. 5.
Tumor movement during (A) full respiratory phases and (B) respiratory gated phases (30∼70%) measured in MIP images.
Fig. 6.
Tumor contoured in (A) CT images for every phase (thick solid for 0%, dotted line for 30%, solid line for 50%), (B) CT images for respiratory gated phases (dotted line for 30%, solid line for 50%) is well encompassed tumor shown in MIP image.
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