Once the desired optical images are captured, the radiographic (Xray) phosphor screen can be moved into the imaging field by simply sliding the screen under the animal chamber (Fig. 1b). The phosphor screen comes into close contact with the thin plastic sheet that supports the animal in the animal chamber, placing the screen essentially at the same focal plane setting used with the optical images. The image capture setting in software is switched to X-ray and the microfocus X-ray generator emits a maximum energy of 35 Kvp for the desired imaging time (typically <30 s). The X-rays are differentially absorbed by bone and soft tissue, creating a projection of the animals anatomical structure on the phosphor screen. The bright-field image of the phosphor screen is captured and digitized in the camera and read into the computer.
As the images of each modality are captured without movement of the animal and with no change in optical focus or zoom, the images can easily be merged or overlayed in the Kodak MI software for precise coregistration.
Multimodal imaging examples
Demonstration of the coregistration of fluorescence and X-ray imaging is shown in Figure 2. The mouse was injected with OsteosenseTM 750, a near-infrared fluorescent diphosphonate probe that binds to bone. This high-resolution image of the animals paw shows the fluorescent signals coming from the probe attached to the digits in the paw (Fig. 2a). The X-ray image details the bones in the digi