Real-time gamma detection identifies radiopharmaceutical extravasation, enabling SUV correction and reducing therapeutic risk

Radiopharmaceutical extravasation, where injected activity remains in soft tissue instead of entering the bloodstream, poses a significant challenge in oncology. This issue can severely compromise quantification in positron emission tomography/computed tomography (PET/CT) by leading to inaccurate Standardized Uptake Value (SUV) measurements, potentially causing misdiagnosis and necessitating repeat examinations. In therapeutic settings, extravasation delivers high local radiation doses, increasing patient risk. A simple, real-time method for detecting these events during administration is crucial to enable immediate management and quantitative correction, addressing a critical gap in current theranostic protocols.

Researchers assessed a real-time monitoring approach using portable gamma detectors during radiopharmaceutical administration. The study was applied to 885 diagnostic PET examinations, utilizing 18F-FDG, 68Ga-DOTATOC/TATE, and 68Ga-PSMA-11, and 15 administrations of 177Lu-DOTATATE therapy. The primary objective was to identify extravasation events and assess the feasibility of deriving SUV correction factors. Dose-rate-time curves were analyzed to establish practical thresholds for extravasation detection, and the impact on patient management and workflow was evaluated.

In the diagnostic cohort of 885 PET examinations, 53 extravasation events were successfully identified and subsequently confirmed on PET images. Analysis of the dose-rate-time curves yielded practical thresholds for reliable extravasation detection: Δpinnor = 0.30 and ΔRt = 388 µSv/h. A statistically significant association was observed between SUV correction factors and specific curve parameters, indicating the potential for prospective adjustment of SUV measurements before image interpretation. This capability is critical for maintaining diagnostic accuracy.

In the therapeutic cohort, one extravasation event was detected during 15 177Lu-DOTATATE administrations, with an estimated absorbed self-dose of 11.6 Gy to the affected region. The real-time monitoring enabled timely intervention, which limited unnecessary radiation exposure and minimized workflow disruption. Feasibility analyses further indicated that for diagnostic procedures, a single detector could be sufficient for both reliable extravasation identification and the derivation of SUV correction factors, highlighting the method's operational simplicity and cost-effectiveness.