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Medical imaging advances on small animals presented at conference

During the SPIE annual meeting in San Diego August 27-31, a researcher discussed the development of single-photon emission computer tomography (SPECT) to examine small animals for medical research.

Bruce Hasegawa of the University of California San Francisco’s Department of Radiology gave a presentation titled “Recent Advances in Small Animal SPECT/CT” during the conference’s Biomedical Imaging session. “It’s really hard to estimate how big this field is going to get,” Hasegawa said.

The mouse is now the dominant animal used in medical research; approximately 90 percent of animals currently used in research projects are mice. Hasegawa noted the applications of SPECT to enhance drug development, a process which currently averages 15 years and $802 million to bring a drug to the consumer phase. That process includes 6 1/2 years of pre-clinical development, 7 years of clinical development, and 1 1/2 years to obtain Federal Drug Administration approval. Between 5,000 and 10,000 candidate compounds are reduced to approximately five compounds for clinical trials before one compound is selected.

Much of the research currently being performed on animals is “invasive;” one animal is sliced up at a specific phase which requires review of a different animal at a later phase. The SPECT technology allows for in vivo examination, meaning that the animal does not die. This allows for serial study on the same animal and requires the use of fewer animals.

SPECT involves the insertion of a biologically active molecule for labeling and a scintillation camera with a pinhole collimator. That provides for a small field-of-view, although with multiple pinholes the necessary detail is increased. “You can build a collimator that has multiple pinholes in it to project a fairly complete image of the anatomy,” Hasegawa noted. “You can greatly improve detection efficiency.”

Hasegawa also noted that SPECT agents have long half-lives. “This is especially important with therapeutic agents,” he remarked.

“Small animal SPECT has the capability to image multiple isotopes,” Hasegawa added.

At this point the focus of SPECT is on research. “Small animal SPECT is a laboratory tool and not a clinical tool,” Hasegawa said.

 

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