Patient-specific Extravasation Dosimetry Using Uptake Probe Measurements

Abstract

Extravasation is a common problem in radiopharmaceutical administration and can result in significant radiation dose to underlying tissue and skin. The resulting radiation effects are rarely studied and should be more fully evaluated to guide patient care and meet regulatory obligations. The purpose of this work was to show that a dedicated radiopharmaceutical injection monitoring system can help clinicians characterize extravasations for calculating tissue and skin doses. We employed a commercially available radiopharmaceutical injection monitoring system to identify suspected extravasation of 18 F-fluorodeoxyglucose and 99m Tc-methylene diphosphonate in 26 patients and to characterize their rates of biological clearance. We calculated the self-dose to infiltrated tissue using Monte Carlo simulation and standard MIRD dosimetry methods, and we used VARSKIN software to calculate the shallow dose equivalent to the epithelial basal-cell layer of overlying skin. For 26 patients, injection-site count rate data were used to characterize extravasation clearance. For each, the absorbed dose was calculated using representative tissue geometries. Resulting tissue-absorbed doses ranged from 0.6 to 11.2 Gy, and the shallow dose equivalent to a 10 cm 2 area of adjacent skin in these patients ranged from about 0.1 to 5.4 Sv. Extravasated injections of radiopharmaceuticals can result in unintentional doses that exceed well-established radiation protection and regulatory limits; they should be identified and characterized. An external injection monitoring system may help to promptly identify and characterize extravasations and improve dosimetry calculations. Patient-specific characterization can help clinicians determine extravasation severity and whether the patient should be followed for adverse tissue reactions that may present later in time.

The Scientific and Clinical Case for Reviewing Diagnostic Radiopharmaceutical Extravasation Long-Standing Assumptions

“…6 Additionally, it has never been easier to characterize extravasations than today. A recent article describes using patient-specific biological clearance and reference tissue volumes (5cc) to quickly assess absorbed dose to tissue ( 7 ).…”

“…We calculated absorbed tissue dose using methods previously described in the literature ( 7 ). When considering extravasations, the calculated dose is for that tissue which contains residual radiopharmaceutical, and the absorbed energy comes from the radiopharmaceutical itself—self dose.…”

“…Using the methods described by Osborne et al ( 7 ), we used the GATE Monte-Carlo framework to simulate absorbed energy per decay for both 18F and 99mTc. Simulations consisted of 5-gram spheres of water uniformly containing 1 MBq of each isotope as an ion source.…”

“…This combination can be found using multiple image-based measurements of the area ( 8 – 13 ), or through measurements with a scintillation counter or other radiation detection system ( 14 ). We used data from external radiation detectors to estimate the effective half-life as described previously by Osborne et al ( 7 ). The external detector data indicates the rate of change of localized radioactivity over time, to which we fit a mono-exponential function to obtain the effective half-life.…”

Detection of Excess Presence of 99mTc-MDP Near Injection Site—A Case Report

“…Significant extravasations can also potentially lead to high absorbed radiation doses to underlying tissue and skin (18). While bone scans and other routine diagnostic studies are often viewed as very low risk to patients, recent research indicates that significant extravasations of routinely used diagnostic radiopharmaceuticals like 99m Tc-MDP can result in high doses to the tissue and adverse tissue reactions (16,18).…”