Scintigraphy of inflammation with nanometer-sized colloidal tracers

Area of Science:

• Nuclear medicine
• Radiopharmacology
• Biomedical imaging

Background:

• Assessing the biodistribution of nanometer-sized colloids is crucial for developing effective radiopharmaceuticals.
• Inflammation can alter tissue permeability, potentially influencing tracer uptake.
• Current diagnostic methods for inflammation may have limitations.

Purpose of the Study:

• To evaluate the biodistribution and uptake of a nanometer-sized 99Tcm-labelled colloid in experimentally induced inflammation.
• To determine the potential of this colloid as a radiopharmaceutical for detecting inflammatory conditions in humans.

Main Methods:

• A 30 nm 99Tcm-labelled colloid was administered intravenously to rats with turpentine-induced abscesses and histamine-induced oedema, alongside a control group.
• Biodistribution was studied 1 hour post-injection.
• The colloid was then administered to patients with arthritis, osteitis, and osteomyelitis for scintigraphic visualization.

Main Results:

• The nanometer-sized colloid showed limited accumulation in oedematous tissue but high uptake in inflamed muscle in rats.
• All inflammatory sites in patients (arthritis, osteitis, osteomyelitis) accumulated the radiopharmaceutical.
• Scintigraphic visualization was successful 45 minutes after administration, correlating with other diagnostic modalities.
• Hyperaemia alone did not cause significant uptake.

Conclusions:

• The uptake mechanism involves regional spilling into the extravascular space through damaged basement membranes.
• Nanometer-sized 99Tcm-labelled colloid is a promising radiopharmaceutical for detecting inflammation, particularly in extremities.
• This tracer offers a convenient method for visualizing inflammatory processes.