QC/QA for Nuclear Medicine Injections

Most nuclear medicine procedures involve an injection. The amount of injected radiotracer is important for the quality and quantification of the image.

Sometimes a paravenous injection of the radiotracer occurs. When the radiotracer is injected or leaks into the tissue surrounding the injection site, it is known as an infiltration or as an extravasation.

An infiltration not only unintentionally exposes the patient’s tissue to more radiation than prescribed, it can also negatively affect the quality and quantification of the images. In PET/CT imaging, precise dose information is necessary to accurately calculate results. Standard practice is to measure the empty syringe in the well counter, so that any remaining radioactivity can be netted from the original syringe value, to establish an accurate net injected dose.

Bolus injections (a volume of fluid injected rapidly) are a standard practice to deliver the radiotracer to the patient’s circulation all at once to start the uptake period. This ensures sufficient 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.

Infiltrations cause PET calculations to be made with erroneous data and therefore can affect PET interpretation and patient management. Infiltrations impact both the dose available to the patient during uptake and the effective length of the uptake period–both key quality indicators. Radiotracer remaining near the injection site means that some portion of the dose is not circulating as required for the full uptake period. Large infiltrations can also expose the patient’s tissue to very high levels of radiation dose.

By providing vital quality control information regarding the injection, the Lucerno system gives the clinicians what they need to determine if an infiltration has occurred and additional information to help characterize the severity. This knowledge helps determine the level of confidence the clinician can have when making patient management decisions based on the nuclear medicine image as well as, helping the clinician understand how much radiation dose was absorbed by a patient’s tissue.

Result: improved patient safety, better quality care, and lower cost.

Infiltrations are surprisingly common

While there is not much public information available on infiltration rates, three large centers have published journal articles indicating their infiltration rate to be between 10% and 20%. Lucerno’s published seven-center quality improvement project results supports the published rate. Automated injectors may reduce the rate, but not to zero. With 18.5 million nuclear medicine scans in the United States each year, Lucerno estimates approximately 2.8 million patients are infiltrated. Of these, approximately 200,000 patients may be harmed by large infiltrations each year in the US.

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 injection site is outside the imaging field of view, so physicians and patients have no idea that an infiltration happened. A recent study indicates that approximately one third of all infiltrations may not be picked up by clinicians reading the scans due to the limits of the field of view. In our experience, the injection site can be out of the field of view even more frequently. In our first 16,000 patient injections, the injection site is likely out of the imaging field of view 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 infiltrations are visible, they are hard to quantify

Even if nuclear medicine static images are visible, they cannot provide true insight into the extent of the infiltration. The Lara System provides information that does not exist today – insight into the extent of remaining radiotracer at the injection area during the uptake process.

Was the injection successful?

Before Lara was available, physicians and patients could not be sure if the injection was ideal.  As a result, patient management decisions may be compromised and patients may be exposed to high levels of unintentional radiation. Lucerno can address this patient safety gap with the Lara® System, a simple tool used in conjunction with the injection process. Lara can provide clinicians with important patient safety and quality information, before the patient is moved to the nuclear medicine camera. By combining Lara’s dynamic data with the static images, the clinician can better characterize the severity of the infiltration before patient management decisions are made.