New starch-based radiotracer for lung perfusion scintigraphy

Area of Science:

• Nuclear medicine
• Radiopharmaceutical development
• Biomaterials science

Background:

• Human serum albumin macroaggregates (MAA) pose microbiological risks for lung perfusion scintigraphy.
• Development of safer alternatives is crucial for diagnostic imaging procedures.

Purpose of the Study:

• To develop a novel Tc-99m radiopharmaceutical based on starch microparticles.
• To evaluate its suitability as a lung perfusion imaging agent, mitigating risks associated with MAA.

Main Methods:

• Oxidised starch coupled to natural polyamine was used to create microparticles for Tc-99m complexation.
• Ready-to-use kits were formulated for simplified, one-step radiolabelling.
• Microparticle characterization included particle-size analysis, electron microscopy, and confocal microscopy.
• In vivo studies involved dynamic scintigraphic acquisitions and biodistribution in Wistar rats.

Main Results:

• Starch microparticles exhibited a homogenous population of spherical/oval shapes, with sizes ranging from 7 to 63 microm.
• Radiochemical purity exceeded 95% and remained stable for at least 8 hours, even in the presence of histidine and human plasma.
• Biodistribution studies in rats showed over 80% of the injected dose accumulating in the lungs within 15 minutes.

Conclusions:

• Starch-based microparticles demonstrated high lung accumulation (over 80% ID at 15 min).
• Key characteristics include a lung half-life of 3 hours, lung-to-vascular ratio of 900, and lung-to-liver ratio of 90.
• These properties indicate the potential of starch microparticles as an effective and safer new lung perfusion agent.