A hybrid functional/anatomical imaging system for high-throughput planar projection mouse imaging
© BioMed Central 2003
Published: 1 October 2003
Imaging the mouse has become a valuable adjunct to genomic and cancer research. Although tomographic techniques such as high-resolution positron emission tomography (microPET) and computed tomography (microCT) are extremely useful, there is also a need for the rapid assessment of mouse anatomy and function at very low radiation doses, with low cost and high throughput. A system was designed using a stimulable phosphor BaFBr imaging plate (commonly called computed radiography [CR]) as the detector. A planar emission image (I-125) is acquired onto one side of the 18 cm × 24 cm CR detector. Subsequent to the emission image acquisition, precise translation of the mouse platform over the CR plate allows the acquisition of an X-ray radiographic image onto the other side of the same CR plate. The image is then read out in a CR reader, which produces a 1770 × 2370 pixel digital image with 0.100 mm pixel pitch. The I-125 and X-ray images are extracted from the larger image, and are mechanically registered, allowing the functional I-125 emission data to be overlaid onto the anatomical X-ray image. Because the CR imaging plates and other required hardware are relatively inexpensive, it is possible that up to 20 mice could be imaged simultaneously using 20 imaging plates, limited only by how many mice can be safely anesthetized and monitored by the technician(s). Once the mice are safely back in their cages, the CR plates can then be read out and the images processed. The overall design of the dual imaging system will be discussed, and the results of a prototype system currently in our laboratory will be presented. Monte Carlo techniques were used to assess the X-ray-associated radiation dose levels with the hybrid imaging system, and the findings suggest that the radiation levels due to the X-ray procedure are far lower than for microCT. We conclude that for appropriate research applications such as monitoring tumor growth over time, or monitoring tumor regression due to therapy, the hybrid imaging system may provide useful tumor kinetic information with high spatial and temporal resolution, and using low radiation dose levels.