Fig. 2
From: Optimal definition of biological tumor volume using positron emission tomography in an animal model
Fused images. Co-registered images from Rat 5 in supine position, with tumor on its back. a Transverse section of the rat through limb (L), spine (S), scapular (SC), and tumor (T). The central white portion of the tumor represents viable tumor areas, while the more peripheral red portion of the tumor represents necrotic tumor areas with hemorrhage. b The corresponding FDG-PET image. c The fused images of a and b, where the FDG-PET image voxel signal intensities closely correlate with the geographic distribution of the viable and necrotic tumor areas. Note the well-overlapped fiducial markers on the dorsal aspect of the tumor. d Four gross tumor areas (GTAs) generated from variable percentages of tumor peak voxels (Cpeak) as well as PERCIST (1.5 × Cliver mean + 2 × Cliver SD) were overlaid onto the histological image: Red represented 70 % of Cpeak, blue represented 50 % of Cpeak, green represented 30 % of C max , and yellow represented the PERCIST based threshold. Among the four GTAs, 30 % Cpeak (green) best delineated the viable portion of the tumor