Abstract
BACKGROUND: (18)F-FDG PET/CT imaging allows to study oncological patients and their relative diagnosis through the standardised 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 study aimed to propose a new technique to monitor and manage these events, to provide an early evaluation and correction to the estimated SUV value through a SUV correction coefficient. METHODS: A cohort of 70 patients undergoing (18)F- FDG PET/CT examinations was enrolled. Two portable detectors were secured on the patients' arms. The dose-rate (DR) time curves on the injected DR(in) and contralateral DR(con) arm were acquired during the first 10 min of injection. Such data were processed to calculate the parameters Δp(in)(NOR) = (DR(in)(max)- DR(in)(mean))/DR(in)(max) and ΔR(t) = (DR(in)(t) - DR(con)(t)), where DR(in)(max) is the maximum DR value, DR(in)(mean) 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 ΔR(t) [(390 ± 26) µSv/h], while ΔR(t) [(150 ± 22) µSv/h] for abnormal and ΔR(t) [(24 ± 11) µSv/h] for normal cases. The Δp(in)(NOR) showed an average value of (0.44 ± 0.05) 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 to 0.573 Gy, according to the segmentation modality. A similar correlation between the inverse of Δp(in)(NOR) and the normalised ΔR(t) 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 early SUV correction when necessary. We also assume that the characterisation 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.