Page 106 - 18F-FDG PET as biomarker in aggressive lymphoma; technical and clinical validation

Chapter 5
Segmentation methods in these studies are generally derived from phantom experiments [4,12], or correlation with pathological specimens in lung cancer [4]. Limited data are available about the differences in ease of use in the lymphoma clinical setting and interobserver reliability of these tumor segmentation methods [10]. Previous studies in DLBCL [10], T cell [14], and Hodgkin lymphoma [15] showed that different segmentation methods, despite having different cutoff values, show comparable accuracy for predicting survival. Therefore, for future use in practice and clinical trials a robust, reliable and easy—i.e., with least required observer interaction—segmentation workflow is necessary. To the best of our knowledge, this is the first pilot study in DLBCL that compares interobserver reliability and ease of use of three workflows for measuring MTV and TLG, and that assesses the effect of manual modification on interobserver reliability.
Materials and Methods
Study Population
Twelve baseline [18F]FDG PET/CT scans from newly diagnosed DLBCL patients with wide variation in number and size of involved organs and lymph nodes lesions were selected from the international PETRA database (http://www. petralymphoma.org). The use of all data within the PETRA imaging database has been approved by the Medical Ethics Review Committee of the VU University Medical Center ( JR/20140414) after patients’ consent to participate in the studies included in the database.
Image Analysis Workflows A and B
Two semi-automated workflows (Workflows A and B) were performed in the same week, by three independent observers using the ACCURATE software tool [16]. Manual modifications of the semi-automatically generated volumes of interest (VOIs) were not allowed initially.The workflow with the best interobserver reliability and ease of use was selected as starting point for manual modification in Workflow C.
Workflow A comprised a user-defined selection of individual lesions.The observers had to select individual lesions (by a single mouse click in the “hottest” part of
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