IRM cerveau de Hyène

Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI)

A 3D in and/or ex vivo imaging approach for anatomical, functional or metabolic analyses.

MRI uses a strong magnetic field and radio waves to create a detailed cross-sectional image of internal organs and structures of the human body, animals in or ex vivo and even on objects containing water molecules.
Currently doctors and researchers continue to refine MRI techniques to assist in medical procedures and research. We use MRI to examine the inside of animals' bodies in detail and in a non-invasive manner.
Here are some examples where MRI is used on the PIXANIM PF:

Brain imaging

The brain of a sheep (or pig or...) is used to study, locate and name different brain areas. The anatomy of a sheep's head below shows fine details that the machine can give.

IRM tête de brebis

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Figure 1: Ewe's head in different planes: Sagittal (A), coronal (B).

From these images, it is possible to extract ultra-precise information which can be used to produce an atlas for example (below) which allows the community of neurobiologists, ethologists, veterinarians etc... as well as the international scientific community (e.g. the Roslin Institute at the University of Edinburgh) to have a common repository  (Magnetic Resonance Imaging, 2015) and (The Journal of Comparative Neurology, 2017) for alternative studies (Animal Frontiers, 2019) and (Psychoneuroendocrinology, 2019).

IRM Atlas cerveau de brebis

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Figure 2: Sagittal section of sheep brain. (A) Lateral (or profile) view of a 3D surface rendering of the gyri segmented from a populationaverage template MR image of sheep brains compared to (B), a paraformaldehyde-fixed ex vivo sheep brain. Note the absence of the olfactory bulbs and the pituitary gland in (B) due to the constraints of ex vivo dissection. Color labels and corresponding gyrus annotations are found in the table to the right.

Furthermore, functional/structural imaging can also be obtained to study connectivity between different brain areas - tractography - (figure 3 below). Tractography is performed using a special MRI technique which is based on diffusion tensor imaging to highlight neural pathways.

tractographie cerveau de brebis

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Figure 3: Tractography in sheep brain. It is a method representating the neural network (fiber tracks) through different colors.

Moreover, it is also possible to study MR Spectroscopy (S) which allows to highlight metabolites present in a specific location. For example, the figure below shows a spetrum of the presence of several metabolites in chicken breast.

SRM in vivo sur filet de poulet

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Figure 4: SRM in vivo in chicken breast. On the spectrum we can see three separate metabolites (from left to right) such as choline, creatine and citrate.

Example of surgery imaging: Knee cartilage imaging

Functional regeneration of articular cartilage remains difficult and it is essential to restore focal osteochondrial defects and prevent secondary osteoarthritis (Nanomedecine: Nanotechnology, Biology, and Medecine, Octobre 2020). By combining autologous stem cells with a therapeutic medical device, it has been possible to develop a two-compartment implant that could promote the regeneration of both articular cartilage and subchondral bone.

IRM cartilage genou defectueux brebis

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Figure 5: MRI on ewe's knee. (A) showing a cartilage defect in the ewe's knee (see white arrow) in comparison with (B) a normal cartilage.

Imaging of vascularisation for blood flow calculation

MRI can be used to calculate blood flow as shown in the following study (Hepatobiliary & Pancreatic Diseases International, 2018).

Imagerie de contraste de phase débit sanguin

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Figure 6: Blood flow rate calculation. (A) Phase contrast imaging, the black dot indicate a cross section of the blood vessel of interest; (B) magnitude image of the same cross section as shown in (A); (C) combination of phase and magnitude image in the vessel in order to calculate the blood flow rate.

In-vivo ovary imaging

In mammalian ovaries, the thec layers of the growing follicles are essential to maintain their structural integrity and support androgen synthesis. By combining postnatal monitoring of the ovaries by abdominal magnetic resonance imaging, endocrine profiling, hormonal analysis of the follicular fluid of growing follicles and transcriptomic analysis of follicle theca cells, it has been shown that exposure of ovine foetuses to excess testosterone activates postnatal follicular growth and strongly affects the functions of the follicle theca in adulthood. (Cellular and Molecular Life Sciences, 2020).

Ovaire agnelle brebis in vivo

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Figure 7: Ewe's pelvis, the ovaries are circled in red, the follicles correspond to the white dots inside the ovaries.

 

Ex-vivo ovary imaging

The IMAGO project proposes to use, at the same time, three ex-vivo imaging modalities: Magnetic Resonance Imaging (MRI), Optical Imaging (OI) and Molecular Imaging by Mass Spectrometry (MMS) in order to analyse the ovary of ewes and to have a visualisation of the distribution of different lipids in its entirety, in 3D.

IRM-ISM ovaire brebis

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Figure 8: Ovary using MRI and MSI. (A) 3D MRI volume rendering technique; (B) 2D section view of follicles' segmentation; (C) 3D volume rendering technique of the segmented follicules; (D) MSI 2D section of the follicles.

Ex-vivo sheep cervix imaging

 

IRM cervix brebis

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Figure 9: MRI of sheep cervix. (A) light 3D MRI volume rendering technique; (B) 3D volume rendering technique of the segmented light (in red); (C) histological sections; (D) a 3D reconstruction.

 

Ex-vivo lung imaging

Bovine tuberculosis caused by Mycobacterium bovis remains one of the most important animal diseases in the world, killing at least 12,500 people a year. In Europe, the prevalence of tuberculosis can be very high in cattle (as in the UK and Ireland) and is increasing in some local areas of France, Spain and Portugal, with a significant financial, social and environmental impact. The eradication of tuberculosis in cattle is urgent. Wildlife often acts as a reservoir for tuberculosis, and the development of oral veterinary vaccines is an international effort to reduce the long-term risks of transmission to cattle in a sustainable way. This objective requires imaging studies of pathological processes in order to test and measure the protective efficacy of vaccines as effectively as possible.

IRM poumon de blaireau

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Figure 10: MRI of a badger lung with bovine tuberculosis in the right median lobe (area stained in red).

Notice that this list is not exhaustive. The use of MRI technology is constantly expanding.

Modification date: 01 August 2023 | Publication date: 06 October 2020 | By: VL