Excretion of FDG into saliva and its significance for PET imaging

Summary

Aim: Assessment of the salivary excretion of FDG and its significance during PET imaging. Methods: Salivary samples from 16 patients were obtained during the first three hours after FDG injection and their activity concentrations were measured. Furthermore, regional FDG accumulations in whole body PET scans (60 min p. i., ROI technique) were determined in the following locations: vestibulum oris, floor of the mouth, hypopharynx, parotid gland, submandibular gland. This ROI analysis was repeated after drinking water (0.2 l) and a second scan (120 min p. i.). Results: The salivary FDG concentrations (SUV) at the first, second and third hour p. i. were 0.2 ± 0.1, 0.4 ± 0.2, and 0.3 ± 0.2, respectively. The FDG uptake in the investigated cranial and cervical sites ranged from SUV 1.2 ± 0.5 in the major salivary glands to 2.1 ± 0.5 in the floor of the mouth. These values remained unchanged after drinking of water. Conclusion: The salivary FDG concentration is higher than expected from the low physiologic content of glucose. This may – similarly to renal excretion – reflect a different behavior of FDG and glucose during reabsorption processes. Nevertheless, the salivary concentration of FDG is so low that no relevant influence on PET imaging is to be expected. Accordingly, the drinking of water prior to the scan is of no benefit for FDG PET imaging of the head and the neck.

Zusammenfassung

Ziel: Untersuchung der Speichelausscheidung von FDG und deren Bedeutung für die Positronenemissionstomographie (PET). Methodik: Von 16 Patienten wurden während der ersten drei Stunden nach FDG-Injektion Speichelproben gewonnen und deren Aktivitätskonzent-ration gemessen. Des Weiteren wurde in GanzkörperPET-Untersuchungen (60 min p. i.) die regionale FDGSpeicherung für folgende Lokalisationen semiquantitativ bestimmt (SUV, ROI-Technik): Vestibulum oris, Mundboden, Hypopharynx, Glandula parotis, Glandula submandibularis. Nachdem der Patient 0,2 l Wasser getrunken hatte, wurde ein zweiter Scan (120 min. p. i.) durchgeführt und die Auswertung für die o. g. Regionen wiederholt. Ergebnisse: Die FDG-Konzentration im Speichel (SUV) betrug in der ersten Stunde p. i. 0,2 ± 0,1, in der zweiten 0,4 ± 0,2 und in der dritten 0,3 ± 0,2. Die FDG-Speicherung in den Regionen von Kopf und Hals reichte von SUV 1,2 ± 0,5 in den großen Speicheldrüsen bis zu 2,1 ± 0,5 im Mundboden.

Keywords

Fluorine-18-fluorodeoxyglucose - positron emission tomography - saliva

Schlüsselwörter

Fluor-18-Fluordeoxyglukose - Positronenemissionstomographie - Speichel

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