Characterization of 'cold' vertebrae on 18F-FDG PET/CT.

Abstract

A photon-deficient ('cold') vertebra on fluorine-18 fluorodeoxyglucose (F-FDG) PET is a known entity and can arise as a result of varying etiologies. A proper interpretation of this observation is required to make an accurate diagnosis for appropriate management. Twelve cases with 'cold' vertebrae on F-FDG PET/computed tomography (CT) were selected and analyzed from a population of 600 patients with a known malignancy who had undergone whole-body F-FDG PET/CT for staging, disease viability assessment, response to treatment, or suspected recurrence purposes. The patterns were studied and correlated with clinical history and the results of the low-dose CT performed with the PET scan for attenuation correction and anatomical localization. The most common cause for cold vertebrae was found to be postexternal radiotherapy, causing photopenia involving multiple vertebrae corresponding to the radiotherapy portals. Two other causes found in the study were the destruction of the vertebral marrow cavity by metastatic tumor cells and vertebral hemangioma. Characteristic features of 'cold' vertebrae have been described in the study with illustrations. Pattern recognition coupled with clinical history and CT correlation of 'cold' vertebrae on F-FDG PET/CT can help in diagnosing the correct underlying etiology, which can help in better management of the patients.