Program Information
Feasibility of Treatment Field Delivery Verification Using Cherenkov Imaging: IMRT and Matched Fields
Y Na , P Black*, C Wuu , Columbia University Medical Center, New York, NY
Presentations
SU-E-601-7 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: 601
Purpose: Cherenkov light emission has been shown to correlate with ionizing radiation dose delivery in solid tissue. An important clinical application of this is the real-time verification of radiation treatment delivery in vivo. To test the feasibility of treatment verification, we acquired Cherenkov images during beam delivery to phantom material, testing two treatment modalities: IMRT and electron-photon matched fields.
Methods: Cherenkov light was captured using a PI-MAX4 intensified charge coupled device system, positioned at 40° relative to the beam central axis. A Varian Trilogy linear accelerator was operated at 6MV and 400MU/min to deliver an Anterior-Posterior beam to a 5cm thick block phantom at 100cm Source-to-Surface-Distance. For matched fields, overlap and gap distances of 2, 5, and 10 mm were delivered and evaluated. IMRT fields were used from patient plans created to treat two sites: lung and brain. Before all beam deliveries the image of a projected light field of 10x10 cm2 was acquired for pixel size calibration in subsequent images. Geometric perspective distortions were corrected using landmark correspondence. Composite images were created through average summation of frames followed by background subtraction. All images were evaluated using ImageJ and Matlab software packages.
Results: Cherenkov images exhibited field size parameter discrepancies of 2-5 mm, depending on the beam delivery characteristics. Specifically, gap width and overlap widths of 5 mm were easily detected, indicating the feasibility of detecting similar errors in a clinical situation involving matched fields. For IMRT field delivery, images reflected the planar dose and MLC leaf positions exported from treatment planning, again indicating the feasibility of verifying accurate treatment delivery in a clinical situation.
Conclusion: Our study indicates that Cherenkov imaging can be used to improve upon current treatment delivery verification techniques, improving our ability to recognize millimeter-scale delivery and positioning errors.
Contact Email: