PET Imaging

Molecular imaging allows visualization, characterization, and measurement of biological processes in vivo at the molecular and cellular levels. Current techniques used for molecular imaging include magnetic resonance (MR) imaging, optical imaging, positron emission tomography (PET), and single photon emission computed tomography (SPECT). Depending on the signal of the detected imaging agent, molecular imaging can enable imaging of specific targets or pathways. As a functional imaging technique, positron emission tomography (PET) observes and measures changes in metabolic processes, including blood flow, regional chemistry, and other physiological activities such as absorption, using radioactive tracers. Different tracers are used for different imaging purposes. PET is a medical scintigraphy technique used in nuclear medicine for medical and research tools in preclinical and clinical settings. It mainly includes tumor imaging and diagnosis of brain diseases. In addition, as a valuable research tool, PET can enhance our understanding of brain and heart function as well as support the development of drugs.

Main concepts of image acquisition and quantification in PET. (Duclos V, et al., 2021)

PET Imaging Agents

With imaging agents, PET can provide physiological and biological information in vivo for disease diagnosis, treatment detection and prognosis assessment. Imaging signals such as metal oxides, fluorescent molecules or radionuclides are available for different imaging modalities. To date, many positron-emitting isotopes are available for PET imaging. Short-lived positron emitters include¹⁵O,¹³N,¹¹C,¹⁸F and ⁶⁸Ga, with half-lives ranging from 2 to 110 minutes, and long-lived positron emitters with half-lives of hours or days, such as ⁶⁴Cu, ⁷⁶Br, ⁸⁹Zr, ¹²⁴I and ⁷⁴As, which can be applied to relatively slow processes and certain effects such as permeability and retention (EPR) effects. To meet the growing demand for molecular imaging, novel PET imaging agents must be developed to improve imaging therapeutics and detection specificity. With the continuous advances in nanotechnology, various nanoparticles (NPs) can be used as PET imaging agents, including but not limited to liposomes, polymers, and dendrimers.

Dendrimer-based PET Imaging Agents

As a nanomaterial, dendrimers have a well-defined structure, highly controllable size, and many functional groups on the surface. In addition. The nanoscale size of dendrimers ensures that they are directly eliminated by the renal system without degradation. These unique features allow dendrimers to be easily used for the construction of nanoscale contrast agents, especially nanoprobes using different positron-emitting radionuclides. Dendrimers can be used as versatile scaffolds for the construction of various PET imaging agents, and their unique structural properties allow for ligand modifications with targeted functions. When constructing PET imaging agents with dendritic macromolecules, isotopes and effective radiolabeling strategies must be considered. Several radiolabeling methods for different isotopes have been successfully developed.

Dendrimer-based imaging probes for dual-mode imaging of ovarian cancer. (Zhao L, et al., 2017)

Application of Dendrimer-based PET Imaging Agents

• Cancer Imaging
  Positron isotope (¹⁸F, ⁶⁴Cu, ⁶⁸Ga)-labeled dendrimers can be used for cancer imaging.
• Cardiovascular and Inflammatory Diseases
  In addition to cancer imaging, PET imaging is also widely used for cardiovascular and inflammatory diseases, such as atherosclerosis, ischemic diseases, and the degree of myocardial viability.
• Drug Delivery
  Since dendrimers can be loaded with a variety of drugs, genes and therapeutic radionuclides, more types of dendrimer therapeutic systems can be developed to expand the application of molecular imaging, especially PET image-guided drug delivery.

How We Can Help

As a trusted CRO, CD BioSciences is committed to providing innovative dendrimer products and high-quality, cost-effective, and hassle-free customization services to customers worldwide. Our dedicated scientists will address each of your specific needs and solve virtually any problem in the development of dendrimer-based imaging agents. If you are interested in our services or have any other questions, please feel free to contact us.

References

1. Duclos V.; et al. PET Molecular Imaging: A Holistic Review of Current Practice and Emerging Perspectives for Diagnosis, Therapeutic Evaluation and Prognosis in Clinical Oncology. Int J Mol Sci. 2021, 22: 4159.
2. Zhao L.; et al. Dendrimer-based contrast agents for PET imaging. Drug Deliv. 2017, 24: 81-93.