Program Information
Evaluation of Tumor Motion Management with Dynamic MRI in Lung Cancer Patients
S Park1 , R Farah1 , S Shea2 , E Tryggestad3 , R Hales1 , J Lee1*, (1) Johns Hopkins University, Baltimore, MD, (2) Loyola University Chicago, Maywood, IL, (3) Mayo Clinic, Rochester, MN
Presentations
SU-K-605-12 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 605
Purpose: To assess tumor motion management strategies using dynamic MRI in radiation therapy of lung cancer patients.
Methods: Dynamic MRI was obtained from 10 lung cancer patients with four MR-compatible external fiducials placed at different locations (two on tumor side, two on non-tumor side) on the patient’s chest. A 4D-MRI was first reconstructed from a multi-slice sagittal 2D-MRI by phase binning and group-wise registration. A two-slice sagittal 2D-MRI was also taken to simultaneously image both the tumor and fiducials. 3D tumor template volumes were obtained from the reconstructed 4D-MRI, and 3D tumor motion was computed by matching the tumor template to 2D-MRI. An external surrogate signal was extracted by matching a 3D model of each fiducial to its segmentation in 2D-MRI. The external surrogate-based tumor tracking approach was evaluated by comparing the computed 3D tumor and fiducial motions. The computed 3D tumor motion was also compared to the 4D-CT-based internal target volume (ITV) to assess ITV-based motion management.
Results: The tumor and the external surrogate signal correlated in general, but often showed a noticeable phase mismatch. The 3D tumor trajectory varied each cycle and the external surrogate signal was not sensitive enough to capture such variation. Furthermore, there are considerable phase mismatch between surrogate signals obtained from different fiducials. On average, 85% of the tumor was moving within the ITV while up to 18% of the tumor was moving outside ITV, implying that ITV may not represent the tumor motion for long duration especially when the tumor motion is large.
Conclusion: Tumor motion management strategies were evaluated using dynamic MRI. Our results show that external surrogate motion has significant variance in relation to tumor motion, and ITV may not represent the long-duration tumor motion well. Motion management strategy should be chosen carefully considering the tumor location and its motion.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by NIH/NCI under the grant R21CA178455.
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