The Bruker BioSpec 70/20 USR Magnetic Resonance Imaging (MRI) System is a state-of-the-art equipment for non-invasive preclinical imaging of small animals. The system is equipped with multiple radio frequency (RF) coils designed for scanning various body parts of small rodents, and is able to deliver high spatial and temporal resolution at the organ, tissue or even molecular level. It is ideal for structural, functional and dynamic imaging for anatomical analysis, assessment of disease progression and optogenetic applications. Contrast agents can be applied to enhance the contrast for cardiovascular imaging and distinguish between normal and pathological tissue. Our Bruker MRI System is also equipped with the MRI CryoProbes, which is a cryogenically-cooled RF probe to further enhance the signal-to-noise ratio of MR images to up to 20 µm with a shorter scan time.
The MRI principle is based on applying a strong magnetic field which causes protons to align to and create magnetic vector oriented along the axis of the magnet. A radio wave is then pulsed through the sample and deflect the magnetic vector. When the radio wave is switched off, the magnetic vector returns to the resting state and release radio wave which is then detected to create magnetic resonance images. The time taken for the protons to fully relax is measured as T1 and T2 relaxation time. T1 relaxation is the time needed for the magnetic vector to return to the resting state; while the T2 relaxation is the time taken for the axial spin to return to the resting state. Different tissues have different proton density and, therefore, can be identified according to the brightness and contrast in T1- and T2- weighted images. For example, tissue with higher fat content appears brighter in T1-weighted images, while tissue with higher water content appears brighter in T2-weighted images. Tissue such as bone cortex and pharynx appears dark in both T1- and T2-weighted images, as they contain very low amount of free protons.
The applications our MRI system cover diffusion tensor imaging (DTI), such as fibre tracking; functional MRI (fMRI), such as brain connectivity and optogenetics; MR spectroscopy (MRS), such as detection of metabolites, amino acids, lipids; angiography and cardiac imaging.
The ULS offers several equipment for non-invasive preclinical imaging. The MRI system offers high image quality for soft tissues with high water content and is radiation-free. However, animals with ferro-magnetic objects implanted cannot be used and the image processing time is relatively long. Our Bruker SkyScan 1276 Micro-CT Scanner is suitable for imaging hard tissues and can generate high-quality spatial images at a relatively high imaging speed. However, the use of X-ray may be harmful to certain living samples. The Fujifilm Ultrasound/Photoacoustic Imaging System employs high frequency sound waves to generate reasonably good images. It has a quick turnaround time, therefore, physiological changes or movement in the animal can be observed instantaneously. The IVIS Lumina Pre-clinical In Vivo Animal Imaging System detects fluorescent and bioluminescent signals from samples. It is easy-to-use and allows simultaneous multi-channel imaging, but the image resolution is relatively low.
