I. Introduction
Akey prognostic factor in patients with early stage cancer is A the metastatic status of the regional nodes draining the primary tumor [1],[2],[3]. The metastasic status of local and distant nodes helps identifying the choice of therapy, tumor staging, and patient outcome. While the FDA-approved 18F-FDG in tumor detection and patient staging has been a triumph of diagnostic imaging, with the exception of large nodes with high uptake, other nodes cannot be visualized in whole-body PET (WB-PET) images. The primary reason is simply the geometry of PET where the detectors are many centimeters away from the lesion of interest and poor sensitivity of these systems that can pick only ~1-3% of all gamma-rays originating from the human body. Reviewing literature indicates that conventional WB-PET can reliably detect lymph nodes (LNs) larger than 1 cm [4] and they have less than 23% sensitivity to detect nodes smaller than 5 mm.