Safety injections of nuclear medicine radiotracers: towards a new modality for a real-time detection of extravasation events and 18F-FDG SUV data correction

Abstract

Background: ¹⁸F-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 ¹⁸F- FDG PET/CT examinations was enrolled. Two portable detectors were secured on the patients' arms. The dose-rate (DR) time curves on the injected DRⁱⁿ and contralateral DR^con arm were acquired during the first 10 min of injection. Such data were processed to calculate the parameters Δpⁱⁿ_NOR = (DRⁱⁿ_max- DRⁱⁿ_mean)/DRⁱⁿ_max and ΔR_t = (DRⁱⁿ(t) - DR^con(t)), where DRⁱⁿ_max is the maximum DR value, DRⁱⁿ_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 Δpⁱⁿ_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 Δpⁱⁿ_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.

Keywords: 18F-FDG; Dosimetry; Extravasation; PET; Radiopharmaceutical; SUV.

Fig. 1

A The RadEye SPRD-ER device. B RadEye is positioned on the injection arm, which in this case is the left arm. C Configuration of signal monitoring procedure during a patient administration by positioning both detectors on the injection (left) and the contralateral (right) arm

Fig. 2

On the left, ¹⁸F-FDG energy spectrum acquired by the RadEye SPRD-ER device during the initial check. On the right, an illustration of an ideal DR-Time curve. The continuous line is the signal acquired on the injection arm; the dashed line is the contralateral signal

Fig. 3

A Example of DR-time curves under normal administration together with the corresponding PET image. B Example of DR-time curves under abnormal administration together with the corresponding PET image. C Example of DR-time curves in case of extravasation together with the corresponding PET image

Fig. 4

The figure shows the trend of ΔR_t with time. A Box plot related to the normal administration cases. B Box plot related to administration with abnormal behaviour. C Box plot related to extravasation cases

Fig. 5

Presentation in boxplot of the Δpⁱⁿ_NOR values for the normal, abnormal, and extravasation cases

Fig. 6

Fitted curves of the inverse of Δpⁱⁿ_NOR (figure a) and ΔR_t.^NOR (figure b) versus SUV correction coefficients presented in Table 2. Ideal and abnormal cases were associated with a cumulative point with an SUV correction coefficient equal to 1

Fig. 7

Potential workflow for real-time detection of extravasation events and SUV correction calculation. In round brackets is indicated the time required to complete the two principal steps of the process