Author: Rashmi Benda, Qinghao Chen, Shifeng Chen, Giovanni Lasio, Peter Olivieri, Huijun Xu, Junliang Xu, Byong Yong Yi, Baoshe Zhang, Jinghao Zhou 👨🔬
Affiliation: University of Maryland Baltimore Washington Medical Group, Department of Radiation Oncology, University of Maryland School of Medicine, Capital Region Medical Center, University of Maryland Shore Regional Cancer Center 🌍
Purpose:
We investigated if the patients receiving lung stereotactic body radiation therapy (SBRT) have adequate planning target volume (PTV) margins by evaluating the intrafraction motion using a fiducial marker.
Methods:
The data were collected from 2 lung SBRT patients with total 10 fractions treated in our institution. One fiducial marker had been implanted near tumor and 5mm PTV margin was used in treatment planning; and during each fraction of treatment, the patients were aligned to the tissue with CBCT images. Prior to the CBCT images, patients were aligned based on tattoos. During the treatment, the intrafraction motion was monitored using triggered kV imaging of fiducial markers which represent the location of target. The distances between fiducial markers in triggered kV imaging to those in DRRs of planning CT are extracted and the PTV margins with and without correction for SBRT are calculated.
Results:
The average of magnitude of distances between fiducial markers in triggered kV imaging to those in DRRs of planning CT is 0.279cm. The PTV margins with and without correction for SBRT are 0.525cm and 0.502cm, respectively.
Conclusion:
The preliminary findings show the 5mm PTV margin used in lung SBRT is adequate based on evaluating the intrafraction motion using a fiducial marker. More patient data will be collected for this study.