Evaluation of tumor progression and detection of new tumors during repeat SRS utilizing the co-registration process of the Leksell Gamma Plan

Jagdish Bhatnagar1, Yoshio Arai2, Douglas Kondziolka, MSc, MD3, Ajay Niranjan, MCh3, Dade Lunsford2, Saiful Huq2

1Pittsburgh, United States 2University of Pittsburgh Cancer Institute, Pittsburgh, USA 3Department of Neurological Surgery, University of Pittsburgh

Keywords: brain metastasis, radiotherapy, gamma knife, Imaging, technique

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     Stereotactic gamma knife radiosurgery is used frequently for the management of patients with brain metastases, and increasingly multiple procedures are performed in the same patient over time. It is often time consuming and difficult to determine the response of previously irradiated tumors, or to identify new tumors when adjacent to older tumors.  
     Our hypothesis was that the image co-registration software in Gamma Plan could be used to efficiently evaluate new images.
     We evaluated 100 treated tumors using this technique.
     The images from the previous SRS were imported into the Leksell Gamma Plan treatment planning system and co-registered with the current images. In the co-registered image when displayed in the red-green color format, the red areas represented new or progressing tumors and the green areas represented stable or regressing tumors. However, in the color blended image, small tumors were difficult to identify. For this the lens technique was used wherein the old and the new images are directly compared. 
     We classified results of 100 treated tumors into five groups related to tumor size: decreased (33%), increased (20%), no change (20%), new tumor (12%), and disappeared (15%). Tumors less than 3 mm in diameter were easily detected in this study.
     This was a retrospective series.
     The technique described in this study allows us to treat metastases with minimal progression and to treat newly discovered tumors less than 3 mm.
     We also can use this approach for efficient decision making to avoid repeat SRS for stable or resolving tumors.


Project Roles:

J. Bhatnagar (), Y. Arai (), D. Kondziolka (), A. Niranjan (), D. Lunsford (), S. Huq ()