Small Animal Imaging
Small animal research is a key translational link between fundamental research and clinical research. Animal models are utilized for essential preclinical in vivo information, such as sample dosage, for many biomedical therapies and devices prior to clinical acceptance.
When conducting preclinical in vivo studies, there are multiple imaging techniques to gather information. X-ray and UV-VIS-NIR detection has been commonly used within medical imaging, each with their own advantages and limitations. X-rays provide good sample penetration but are unable to give soft tissue information. UV and visible wavelengths can provide soft tissue information but are limited by penetration depth due to the high scattering of these wavelengths within tissue.
Near infrared (NIR) wavelengths are advantageous as they have reduced scattering within biological soft tissue and are thus used for preclinical in vivo studies. NIR can be separated into two distinct windows, with NIR-I encompassing wavelengths in the 750-1060 nm range, and NIR-II encompassing wavelengths in the 1060-1700 nm range. NIR-I wavelengths can be imaged via silicon CCDs but are only able to penetrate a few millimetres into soft tissue. NIR-II can penetrate deeper into tissue, due to reduced light scattering and autofluorescence, but can only be detected by InGaAs cameras. NIR-II methods have recently been developed for small animal imaging to investigate predominately early disease detection. Majority utilize fluorophores, such as single-walled carbon nanotubes and quantum dots, that fluoresce in the NIR-II region.
Integrated Systems for Small Animal Imaging
In vivo Raman scatting in the NIR wavelength region, used for cancer diagnostics, image-guided surgery and biosensing, requires high sensitivity over the 650-1350 nm region. The TPIR 785 offers NIR optimized technology, with high-throughput and high performance over the 80-3650 cm-1 spectral range for real-time, non-destructive data acquisition.
As a complete system, the TPIR 785 is fully integrated, with incorporated NIR optimized spectrometer, low-noise camera and a 785-laser source. With multiple camera options, the TPIR 785 can be combined with either a standard, broad range CCD sensor, or a high NIR sensitivity CCD sensor.
The TPIR 785 comes with an assortment of accessories, such as a 785 nm Raman probe, cuvette holder, and filter chamber, which are easily switchable to tailor the system for multiple in vivo applications.
Cameras for Small Animal Imaging
NIR-II fluorescence is used within small animal imaging due to penetration depth and reduced scattering, however a typical silicon based sensor cannot image those wavelengths. The NIRvana family of InGaAs camera features high sensitivity in the 900 – 1700 nm range, ideal for capturing low-light NIR-II/SWIR fluorescence from small animal fluorescence probes.
Noise is reduced with the NIRvana as it is thermoelectrically cooled, with temperatures reaching as low as -85℃, providing the lowest level of dark noise for small animal imaging. The cryogenically cooled NIRvana LN camera is also available, reaching temperatures of -190℃.
With high signal-to-noise ratios up to 250 full frames per second, the NIRvana family allows for fast capture of fluorescence even with extremely low exposure times.
Small animal optical imaging relies on light emitted from molecular probes within the animal. The PI-MAX4 combines the advantages of EMCCDs and ICCDs to deliver excellent precision timing, sensitivity, intelligence and speed for measuring in vivo fluorophores.
The PI-MAX4 offers high quantum efficiency in the wavelength region of 200 – 900 nm, encompassing the NIR-I window.
The coupling of the EMCCD to an image intensifier allows for a 6x higher light throughput between the image intensifier and the detector in comparison to lens-coupled configurations. This ensures imaging of even the faintest fluorophores.
For small animal spectroscopy, highly sensitive NIR spectroscopy is required. The BLAZE CCD cameras are able to offer this high sensitivity alongside low dark current.
The BLAZE delivers fast spectral rates to capture all available information alongside True -100℃ cooling. This level of deep cooling provides low spectral noise, ideal for low light applications and long exposure times – two experimental parameters useful for small animal imaging.