Room: Exhibit Hall | Forum 5
Purpose: Tumor tracking during radiotherapy can allow for better treatment accuracy, dose conformity and sparing of healthy tissue. Many methods have been introduced to tackle this utilizing multiple modalities, including the use of the on-board kV imager and internal or external surrogates. Another method is to use the on-board portal imager which is a challenging task due to the inherent decrease in image quality, however this method does not result in additional dose to the patient or rely on accurate correlation between surrogate and tumor motion. A survey of the current literature suggests that tracking algorithms are often demonstrated on a single treatment modality or tumor location.
Methods: We present the further development of the markerless tracking algorithm, utilizing the on-board portal imager of the treatment machine, allowing this method to be implemented in dynamic treatment environments while preserving the application to IMRT treatments published previously. The core of the algorithm is a template matching method and relies on template stability metrics and local relative orientation to perform multiple feature tracking simultaneously. Only a single image is required to initialize the algorithm and features are automatically added, modified or removed in response to the input images.
Results: The tracking algorithm was run successfully on both an IMRT lung treatment and a VMAT prostate treatment with fiducials. The tracking error for the lung patient case agrees with previous publications (2mm) and for the prostate case with fiducial markers is comparable with others in the literature (0.5mm).
Conclusion: A multi-region, markerless tracking algorithm has been developed, capable of tracking multiple features simultaneously without the requirement of a training period and has been shown to be robust in complex tracking environments.
Funding Support, Disclosures, and Conflict of Interest: This work was supported, in part, by award number R01CA188446 from the National Institutes of Health and a research grant from Varian Medical Systems, Inc.