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In vivo luminescence imaging

May 28, 2019 |
The Centre for Microscopy and Molecular Imaging (CMMI) has updated its luminescence imaging equipment. The new machine is multimodal, modular, more powerful, and can produce images of more subjects.

In late 2018, CMMI acquired a PhotonIMAGERTM Optima. ‘Our new luminescence imaging machine(1) is more sensitive than the one it replaces’, comments Lionel Larbanoix, head of CMMI’s non-ionising molecular imaging department. ‘It has a larger chamber that lets us image up to ten mice at the same time, or a hundred each day. This makes our results more statistically sound, and lets us be more confident in the results of our studies.’

Other benefits
The new machine offers more improvements:
• It is modular. Two modules are currently fitted onto it: ‘Macrolens’, which can zoom in on a small area, and ‘4View-3D’, which enables subject animals to be examined simultaneously from 4 sides.
• Luminescence imaging is harmless. The same animal can go through the machine multiple times.
• It is an in vivo imaging technique that is cheap and easy to deploy.
• The new machine was installed in an area that is certified for radionuclear imaging, which means that radioisotopes may be used.

Bioluminescence imaging
The new machine is multimodal, and can visualise three types of luminescence. The most frequently used one (accounting for 90% of the machine’s activity) is bioluminescence imaging (BLI). ‘Bioluminescence is the result of a biochemical reaction between luciferase and luciferin’, explains Lionel Larbanoix. ‘It can be observed in nature, for instance in glowworms. BLI involves modifying cells in vitro so that they express luciferase(2), and implanting them in the subject. Then, the modified cell lines will emit light if you inject luciferin.’
BLI is very helpful to monitor the evolution of cancer cells, stem cells, parasites, etc., and to see how they react to a certain drug, for instance.

Fluorescence and Cherenkov luminescence
Fluorescence imaging (FLI) can be used to detect meaningful biomarkers with targeted fluorophores. ‘FLI is used for similar applications as nuclear imaging, such as the detection of biomarkers linked to cancer, inflammation apoptosis, etc., except it does not rely on radioisotopes.
Cherenkov luminescence imaging (CLI) is more marginal, and it can show the biodistribution of certain radioisotopes that emit blue light but that cannot necessarily be seen using conventional nuclear imaging techniques (PET and SPECT). These include yttrium-90 (90Y), for instance. CLI can be used to check that this radioisotope used in radiation therapy—coupled with the adequate antibody—has attached itself to the target tumour.

Notes:
(1) Luminescence is the emission of energy as light (photons) from a molecule undergoing excitation.
(2) No terrestrial vertebrate has cells that naturally express luciferase.

Candice Leblanc