Positron Emission Tomography Using 64-Copper as a Tracer for the Study of Copper-Related Disorders

Summary

The present protocol describes how to perform ⁶⁴Cu PET/CT and PET/MRI imaging in humans to study copper-related disorders, such as Wilson disease, and the treatment effect on copper metabolism.

Abstract

Copper is an essential trace element, functioning in catalysis and signaling in biological systems. Radiolabeled copper has been used for decades in studying basic human and animal copper metabolism and copper-related disorders, such as Wilson disease (WD) and Menke's disease. A recent addition to this toolkit is 64-copper (⁶⁴Cu) positron emission tomography (PET), combining the accurate anatomical imaging of modern computed tomography (CT) or magnetic resonance imaging (MRI) scanners with the biodistribution of the ⁶⁴Cu PET tracer signal. This allows the in vivo tracking of copper fluxes and kinetics, thereby directly visualizing human and animal copper organ traffic and metabolism. Consequently, ⁶⁴Cu PET is well-suited for evaluating clinical and preclinical treatment effects and has already demonstrated the ability to diagnose WD accurately. Furthermore, ⁶⁴Cu PET/CT studies have proven valuable in other scientific areas like cancer and stroke research. The present article shows how to perform ⁶⁴Cu PET/CT or PET/MR in humans. Procedures for ⁶⁴Cu handling, patient preparation, and scanner setup are demonstrated here.

Introduction

Copper is a vital catalytic cofactor that drives multiple important biochemical processes essential for life, and defects in copper homeostasis are directly responsible for human diseases. Mutations in the ATP7A or ATP7B genes, encoding copper-transporting ATPases, cause Menke's and Wilson diseases, respectively. Menke's disease (ATP7A) is a rare lethal disorder of intestinal copper hyperaccumulation with severe copper deficiency in peripheral tissues and deficits in copper-dependent enzymes¹. Wilson disease (WD) (ATP7B) is a rare disease characterized by the inability to excrete excess copper to bile....

Protocol

A few clinical trials using this ⁶⁴Cu PET/CT or PET/MRI protocol have been approved by the Regional Ethics Committee of Region Midt, Denmark [1-10-72-196-16 (EudraCT 2016-001975-59), 1-10-72-41-19 (EudraCT 2019-000905-57), 1-10-72-343-20 (EudraCT 2020-005832-31), 1-10-72-25-21 (EudraCT 2021-000102-25), and 1-10-72-15-22 (EudraCT 2021-005464-21)]. Written informed consent was obtained from the participants at enrollment. The inclusion criteria for all participants were age >18, and for females the use of safe contraception. The exclusion criteria for Wilson disease patients were decompensated cirrhosis, a Model for End-stage Liver Disease (MELD) sco....

Results

Dose calculation
Based on dosimetry calculations, the effective radioactivity dose for IV administration is 62 ± 5 µSv/MBq tracer¹⁰. Thus, a 50 MBq dose is recommended depending on the time frame. Up to 75-80 MBq is applicable for longer examinations and provides good-quality images without exceeding an ethically approved dose. The effective dose for oral administration is 113 ± 1 µSv/MBq tracer, due to intestinal accumulation of the tracer. Thus, a lower dose needs to be cons.......

Discussion

The method is like any other PET method, but the long half-life of 12.7 h offers the opportunity to investigate long-term copper fluxes (we have good results from up to 68 h after IV tracer injection). All steps in the protocol must be handled by personnel familiar with PET, although they are no more critical than any other PET examination.

Troubleshooting
Because we often use ⁶⁴Cu for long-term investigations, the PET signal will be noisier than usual. This i.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.22 micrometer sterilizing filter	Merck Life Science
Cannula 21 G 50 mm	BD Microlance	301155
Cannula 25 G 16 mm	BD Microlance	300600
Dose calibrator	Capintec CRC-PC calibrator
PET/CT scanner	Siemens: Biograph
PET/MR scanner	GE Signa
PMOD version 4.0	PMOD Technologies LLC
Saline solution 0.9% NaCl	Fresenius Kabi
Sodium acetate trihydrate BioUltra	Sigma Aldrich	71188
Solid 64CuCl2	Danish Technical University Risø
Sterile water	Fresenius Kabi
Venflon 22 G 25 mm	BD Venflon Pro Safety	393280