Background 18F-FDG PET/CT imaging allows to study oncological patients and their relative diagnosis through the Standardized Uptake Value (SUV) evaluation. During radiopharmaceutical injection, an extravasation event may occur, making the SUV value less accurate and possibly leading to severe tissue damage. The aim of the study was to propose a new technique to monitor and manage these events, in order to evaluate a correction to the calculated SUV value. Methods A cohort of 70 patients undergoing 18F- FDG PET/CT exams was enrolled. Two portable detectors were secured on the patients' arms. The dose-rate (DR) time curves on the injected DRin and contralateral DRcon arm were acquired during the first 10 minutes of injection. Such data were processed to calculate the parameters ΔpinNOR= (DRinmax- DRinmean)/ DRinmax and ΔRt= (DRin(t) - DRcon(t)), where DRinmax is the maximum DR value, DRinmean is the average DR value in the injected arm. OLINDA software allowed dosimetric estimation of the dose in the extravasation region. The estimated residual activity in the extravasation site allowed the evaluation of the SUV's correction value and to define an SUV correction coefficient. Results Four cases of extravasations were identified for which ΔRt [(390 ± 26) µSv/h], while ΔRt [(150 ± 22) µSv/h] for abnormal and ΔRt [(24 ± 11) µSv/h] for normal cases. The ΔpinNOR showed an average value of 0.44 for extravasation cases and an average value of (0.91 ± 0.06) and (0.77 ± 0.23) in normal and abnormal classes, respectively. The percentage of SUV reduction (SUV%CR) ranges between 0.3% and 6%. The calculated self-tissue dose values range from 0.027 Gy to 0.573 Gy, according to the segmentation modality. A similar correlation between the inverse of ΔpinNOR and the normalised ΔRt with the SUV correction coefficient was found. Conclusions The proposed metrics allowed to characterised the extravasation events in the first few minutes after the injection, providing an SUV correction when necessary. We also assume that the characterization of the DR-time curve of the injection arm is sufficient for the detection of extravasation events. Further validation of these hypotheses and key metrics is recommended in larger cohorts.