Zinc imaging could be used to track a spate of diseases

A preliminary imaging study with Zn-63 zinc citrate confirmed a protocol for preparation and showed encouraging preclinical biodistribution. This technique holds promise for a wide variety of diseases involving zinc disorder, including a range of cancers and metabolic disorders, according to a study published July 21 in the Journal of Nuclear Medicine.

In addition to being able to image zinc deficiency, zinc imaging has the potential to be used as a radiotracer for the imaging of metabolic syndrome and diabetes; and a number of cancers, including pancreatic, breast and prostate cancer. Additionally, some Alzheimer’s research has pointed to a potential therapy in metal chelation, whereby clinicians seek to dial down zinc and copper binding with beta-amyloid in the brain. Zinc imaging could be a useful tool for the development of this therapy.

“Clearly, a non-invasive method to measure zinc dynamics in the body would be of high interest for understanding the pathophysiology of a broad range of diseases,” wrote Timothy R. DeGrado, PhD, from the Mayo Clinic in Rochester, Minn., and colleagues. “It may also be useful for monitoring therapies that are directed at changing zinc homeostasis.”

DeGrado’s team evaluated the appropriate methodology for preparation of the radiotracer. The researchers used solutions of Cu-63 copper nitrate in dilute nitric acid and irradiated it with protons in a cyclotron. The Zn-63 is then procured by automated purification in the target solution. The solution is further processed and Zn-63 eluted in a solution of mostly acetone and neutralized before being captured in a carboxymethyl cartridge, rinsed and eluted with isotonic 4 percent sodium citrate.

Zn-63 is not the only possible tracer for zinc PET imaging, but it is the most feasible due to the ability to produce it in a cyclotron and due to improved decay rates over other zinc tracers. Results of the preclinical PET imaging portion of the study showed normal biodistribution. However, additional studies will need to be conducted before zinc PET could enter general clinical practice.

“Zn-63 PET represents a new tool to begin to evaluate zinc transport in these various disease states and the effects of zinc-related therapies. Although the 38.5-minute half-life of Zn-63 will limit measurements of slower (more than two hours) intracellular zinc turnover times, it is anticipated that dynamic PET imaging data may provide quantitative assessments of transport and more rapid turnover processes.”