Quality and Dosimetry for Nuclear Medicine Administrations

Most nuclear medicine procedures involve an injection or an infusion of a radiopharmaceutical. The amount of administered radioactivity is critical to the quality of the procedure.

An infiltration (paravenous injection) is the inadvertent administration of a pharmaceutical into the tissue instead of the vein, as intended. Although an extravasation is typically defined as an infiltration of a vesicant, an infiltration of a radiopharmaceutical can be considered an extravasation due to the effects of ionizing radiation on patient tissue.

An extravasation not only unintentionally irradiates the patient’s tissue with more radiation than prescribed; it can also negatively affect the quality and quantification of the images. In many nuclear medicine procedures, precise dose information is necessary to accurately generate quantitative results.  Standard practice is to measure the empty syringe in the well counter. Any residual radioactivity is subtracted from the original assayed value to establish an accurate net administered dose.

For many diagnostic imaging procedures, bolus injections (a volume of fluid injected rapidly) are a standard practice to deliver the radiopharmaceutical into the patient’s circulation. This ensures sufficient image contrast at time of imaging. Delivering a bolus also helps ensure consistency in the length of the uptake period, when comparing one image to another image.

Extravasations cause quantification errors that can affect image interpretation and patient management. They impact both the dose available to the patient during uptake and the effective length of the uptake period–both key quality indicators. Radiopharmaceutical remaining near the administration site means that some portion of the radioactivity is not circulating as required for the prescribed uptake period. Large extravasations can also irradiate the patient’s tissue with high absorbed doses of radiation.

For therapeutic procedures, an extravasation prevents the complete delivery of the prescribed dose.

By providing vital quality control information regarding the administration, the Lara System provides clinicians what they need to determine if an extravasation has occurred and additional information to help characterize the severity. This knowledge helps determine the level of confidence clinicians can have when making patient management decisions based on the nuclear medicine imaging or therapeutic response.

Result: less variable image quality, more confidence in therapy delivery, and improved patient safety.

Extravasations are surprisingly common

While there is not much public information available regarding radiopharmaceutical extravasation rates, 12 centers have published their extravasation rates (average of 15.5%). A recent quality improvement project of radiopharmaceutical administrations in seven centers involving 2531 patients supports the previously published extravasation rates. With 18.5 million nuclear medicine procedures in the United States each year involving ~30M radiopharmaceutical administrations, it is likely 4.5M patients are extravasated every year. Of these, ~500K+ patients may be harmed by significant extravasations* each year.

*Company estimates based on 22,000+ monitored injections

1367 patients
The quantitative evaluation of patient studies revealed that paravenous injection is a relatively frequent effect (18%).
Silva-Rodríguez, et al
Medical Physics

In many nuclear medicine studies, the administration site is outside the imaging field of view, so physicians and patients have no idea that an extravasation happened. A recent study indicates that approximately one third of all extravasations may not be visible to clinicians interpreting the images based on the imaging field of view (FOV). In our experience, the administration site can be out of the field of view even more frequently. In over 22,000 procedures monitored with the Lara System, the administration site is likely out of the FOV in ~50% of the images.

400 patients
We conclude dose extravasations were commonly encountered (10.5%) in PET/CT. However, it is underreported by at least 31% due to omitting injection site from the FOV. When present, extravasations may lead to underestimation of SUVmax.
Osman, et al

Even if extravasations are visible, they are hard to quantify

Even when extravasations are in the FOV, the static image cannot provide true insight into the extent of the extravasation over time. The Lara System provides dynamic insight that static images cannot provide. The Lara System detects changes in the extravasation during the uptake process. 

Was the administration successful?

Without Lara or repeated imaging during the uptake process, physicians and patients cannot be sure if the administration was ideal.  As a result, patient management decisions may be compromised, and patient tissue may be irradiated with high levels of unintentional radiation. The Lara System can address this patient safety gap.  Lara is a simple tool that can alert clinicians with important patient safety and quality information to help mitigate the effects of an extravasation early in the uptake process. By combining Lara’s dynamic data with the static images, clinicians can better characterize the severity of extravasations before patient management decisions are made.