Program Information
Feasibility of Kilo-Voltage Projection-Based Real-Time Tracking of Intrafractional Patient Motion During Spine Stereotactic Radiosurgery Or Stereotactic Body Radiation Therapy
J Kim1 , Y Park2 , G Sharp3 , B Winey4*, (1) Massachusetts General Hospital, Boston, MA, (2) UT Southwestern Medical Center, Dallas, TX, (3) Massachusetts General Hospital, Boston, MA, (4) Massachusetts General Hospital, Boston, MA
Presentations
TH-AB-205-2 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 205
Purpose: To develop a real-time tracking method for vertebral targets during spine stereotactic radiosurgery (SRS) and evaluate the clinical feasibility of the proposed spine tracking method.
Methods: Using real-time kV projection streaming within XVI (Elekta XVI), kV projection-based tracking was applied to the target vertebral bodies. Two-dimensional in-plane patient translation was calculated via an image registration between digitally reconstructed radiograph (DRR) and kV projections. DRRs were generated from the registered pretreatment CBCT, which represented the patient geometry aligned prior to treatment using a six degrees-of-freedom robotic couch system. During a mid-treatment CBCT, each kV projection was streamed for an intensity gradient-based image similarity metric image registration to the offset DRR. The ground truth displacement was calculated at the beam isocenter using the couch correction applied to the patient setup after the mid-treatment CBCT acquisition. The resulting translation by the DRR-projection registration was compared to the ground truth displacement. The proposed tracking method was retrospectively evaluated using five spine patients received spine SRS. The tracking method was real-time tested for one spine SRS patient.
Results: The couch correction applied after the mid-treatment CBCT acquisition was (-0.2 ± 0.5, 0.1 ± 0.6, 0.2 ± 0.5) mm and (0.1 ± 0.8, 0.2 ± 0.4, 0.2 ± 0.6) ° for all patients. The absolute 2D difference between the ground truth and resulting translations was (0.6 ± 0.3, 0.2 ± 0.2) mm, demonstrating that the real-time in-plane patient motion was detected with sub-millimeter accuracy. The intrafractional motion was within 3 mm for all the patients considered.
Conclusion: It was demonstrated that the proposed spine tracking method has a capability to track the intrafractional motion in real-time with sub-millimeter accuracy.
Funding Support, Disclosures, and Conflict of Interest: This study was supported by the Elekta Motion Management Grant.
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