Program Information
Spatial Co-Localization of F-18 NaF Vs. F-18 FDG Defined Disease Volumes
P Ferjancic1*, S Harmon1 , S Chen2 , U Simoncic3 , R Jeraj1 , (1) University of Wisconsin, Madison, WI, (2) 1st Hospital of China Medical University, Shenyang, Liaoning, (3) Jozef Stefan Institute, Ljubljana
Presentations
WE-H-207A-5 (Wednesday, August 3, 2016) 4:30 PM - 6:00 PM Room: 207A
Purpose:
Both [F-18]NaF and [F-18]FDG show promise for quantitative PET/CT assessment in metastatic prostate cancer to bone. Broad agreement between the tracers has been shown but voxel-wise correspondence has not been explored in depth. This study evaluates the spatial co-localization of [F-18]NaF PET and [F-18]FDG PET in bone lesions.
Methods:
Seventy-three lesion contours were identified in six patients receiving dynamic NaF PET/CT and FDG PET/CT scans two hours apart using identical fields-of-view. Tracer uptake (SUV) reflecting 60 minutes post-injection was modeled from kinetic parameters. Lesions were segmented by a physician separately on NaF PET and FDG PET. PET images were rigidly aligned using skeletal references on CT images. Lesion size, degree of overlap, voxel-wise tracer uptake values (SUV), and CT density distributions were compared using Dice coefficient, Positive Predictive Value (PPV), and Spearman rank correlation tests.
Results:
Across all patients, 42 lesions were identified on NaF PET (median 1.4 cm³, range <1-204 cm³) compared to 31 using FDG PET (median 1.8 cm³, range <1-244 cm³). Spatial co-occurrence was found in 25 lesion pairs. Lesions on NaF PET had PPV of 0.91 and on FDG a PPV of 0.65. Overall, NaF-defined lesions were 47% (±24%) larger by volume with moderate overlap to FDG, resulting in mean Dice coefficient of 34% (±22%). In areas of overlap, voxel-wise correlation of NaF and FDG SUV was moderate (ρ=0.56). Expanding to regions of non-spatial overlap, voxels contained in FDG-only contours were almost exclusively low HU (median 118), compared to dense regions of NaF-only voxels (median 250). In sclerotic sub-volumes (HU > 300) NaF-defined contours encompassed 83% of total FDG volume.
Conclusion:
Moderate voxel-wise correlation of FDG and NaF PET/CT uptake was observed. Spatial discrepancies in FDG and NaF PET/CT imaging of boney metastases could be influenced by poor sensitivity of FDG PET/CT in sclerotic regions.
Funding Support, Disclosures, and Conflict of Interest: Funded by Prostate Cancer Foundation
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