Gene Therapy - Core Facilities: Animal Imaging

Animal Imaging
Core Facility

MicroPET Imaging System
The Core Facility is purchasing small animal MicroPET Imaging System from Concorde Microsystems, and is expected to arrive in January 2003. Small animal models, particularly genetically engineered mice, are increasingly recognized as powerful discovery tools in cancer, cardiac, pharmacological and neurological research. PET imaging techniques are an important tool for providing data about biochemical, genetic, or pharmacological processes in vivo, and can be performed repetitively in the same animal. Many animal research models suffer from the critical limitation that animals must be sacrificed in order to perform tissue or molecular analysis before the full or long-term implications of the research becomes evident. This prevents researchers from observing in vivo the natural or induced evolution of the processes under study. The PET Imaging Center at LSUHSC-Shreveport's is among the few PET Centers in the world with a a cyclotron onsite capable of producing the radiotracers used in PET imaging. The Scientific Staff at the PET Imaging Center will produce the radioisotopes necessary to generate animal PET data and assist in interpretation of images.

MicroCT Imaging System
alysis.The MicroCAT II in-vivo X-ray micro-CT Scanner (Imtek Inc., Knoxville, TN), is an in-vivo X-ray CT scanner providing isotropic voxel resolutions as high as 15 microns and systems for respiratory- and cardiac-gated data acquisition. The system is configured with a 2048 x 3096, 2element CCD array coupled to a high-resolution phosphor screen thermo-electric cooled detector providing an imaging areas (transaxial x axial) of 50mm x 90mm and pixel size as small as 30 micron x 30 micron. The X-ray source a tungsten anode material with a maximum voltage of 80 kVp, providing a focal spot as low as 9 micron. Data acquisition is capable of up to 5 frames per second (detector dependent) and up to 16 Mega pixels per frame (detector dependent). The reconstructed volume is prodiced from fan beam and cone beam (Feldkamp) filtered back projection algorithms. The image circle is from 35mm up to 110 mm diameter (transaxial field-of-view). The reconstructed volume resolution is as low as 15 micron (10% MTF). An integrated Windows NT based graphical user interface is included for data acquisition, image reconstruction, and AmiraTM (Indeed - Visual Concepts GmbH) data visualization software (includes 3D volume rendering,arbitrary 2D slice visualization, volumetric segmentation tools, etc.). In addition, Beowolf-cluster compatible version of the 3D Feldkamp cone-beam reconstruction software is available. The system is capable of real-time reconstruction engine to reconstruct volumetric data in parallel with scan.

Bioluminescence/Fluorescence Imaging
Xenogen IVIS™ Imaging System includes:
• Low noise, large format CCD camera
• Xenogen imaging chamber
• High sensitivity f/0.95 lens
• Windows® control computer with high-resolution monitor
• WaveMetrics IGOR Pro™ and Xenogen’s Living Image® software (Windows® and Macintosh® compatible)
• Operation manual
• Optional lab workbench or carts available

Operation of the IVIS™ Imaging System is simple and straightforward. Power the system up, and cool the camera. Make sure the acquisition computer is on and the Living Image® software is running. Click “Initialize” in the Camera Control panel (as shown below). Place the anesthetized animal or animals on the shelf in the imaging chamber and close the door. Check the “Live” box in the Camera Control panel. A video image of the sample will appear on the monitor. If you need to reposition the specimen, turn the “Live” image off first. If necessary, adjust the field of view and focus with the “FOV” and “Focus” controls, also in the Camera Control panel. Change the illumination level with the dial on the front of the sample box. Click “Overlay” in the Camera Control panel, and set the exposure time for the luminescent image. Finally, click “Acquire” in the Camera Control panel, and the system will take a picture per your settings and display the data as an overlaid image. The camera creates two images: one black-and-white (or grayscale) background photo of the mouse and a color overlay of the emitted photon data, as shown to the right above. The CCD in the IVIS camera is a photon detector — it detects photons and assigns a numeric value to each pixel corresponding to the number of photons at that location. The emitted-photons image is generated by detecting photons accumulated during the exposure time — from a few seconds to a few minutes — resulting in a two-dimensional array of data. The visual representation of these data appears as a “pseudocolor” image, representing the relative numbers of detected photons, overlaid on the black-and-white background image of the animal. While the numerical photon data in the image file are recorded and constant, the color display can be modified to best visualize the data by using Living Image® software created by Xenogen Corporation. The color of the rainbow spectrum corresponds to a range of detected photons — lowest values indicated as purple, highest value assigned as red. The color range display can be modified with Living Image® software, while the numerical photon data in the image file remain unchanged.

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