NORTHRIDGE, Calif.—Imaging specialist Gamma Medica-Ideas (GM-I) recently announced the installation of a FLEX preclinical SPECT/CT system at the Houston-based MD Anderson Cancer Center. The new system will allow Dr. Juri Gelovani, chairman of experimental diagnostic imaging, and his colleagues to develop new methods for imaging tumors for cancer diagnosis and monitoring the targeting and efficacy of tumor-specific drugs.
While traditionally considered a hospital technique more suited to diagnosing disease in human patients, SPECT/CT and PET are seeing increased application in the laboratory setting, as a way to monitor molecular events within living organisms of varying shapes and sizes.
"For many, many years, researchers have been conducting biodistribution and other studies by sacrificing animals and studying tissue samples," says Patrick Moody, GM-I vice president, marketing. "Only in the last few years have researchers started to learn about the tremendous advantages of in vivo imaging."
In vivo imaging allows researchers to watch biological processes in real time, he says. And because the same animal can be watched over time in a single experiment, the techniques eliminate study variables that occur because of physiological differences between animals.
Perhaps more importantly, Gelovani adds, the system allows for sequential SPECT and CT imaging and generation of SPECT/CT fusion images of an experimental animal within the same system without repositioning of an experimental animal.
"Before this instrument became available, experimental animals had to be imaged on separate SPECT and CT systems, which often resulted in imprecise co-registration of the two image datasets," he explains. "This system is perfectly suited for the development of biodistribution and radiation dosimetry data in rodents that is required for filing of an IND for the FDA."
According to David Wilk, GM-I senior vice president, sales, as more researchers are becoming trained in in-vivo imaging techniques, use of the technology is rapidly becoming more widespread. According to a recent report by Canadian imaging specialist Advanced Research Technologies, preclinical imaging systems are expected to increase their share of the preclinical analytical instrument market to 30 percent by 2008, a compound annual growth rate of 26 percent.
At the same time that application of in-vivo imaging systems becomes more prevalent, regulatory agencies are beginning to feel increased pressure to accept data from these experiments as definitive end points in new drug applications.
According to Gelovani, a variety of SPECT radiolabeled agents that are currently being used in the clinic can be now applied in preclinical research for imaging experimental tumors models and models of other diseases in rodents, such as CNS and cardiovascular diseases. The regulatory agencies, however, have yet to catch up to the technical achievements.
"Currently, these imageable biomarkers are not being used as sole indicators of treatment response or as the endpoints in new drug filings, because the majority of novel imaging agents had not undergone Phase III multi-center validation studies yet," he says. "Two experimental agents, one therapeutic and another imaging, cannot be studied within the same experimental protocol, according to the FDA regulations."
"Biotech and pharmaceutical companies have already used in vivo imaging data in IND applications," Moody says. "In vivo imaging is not yet the standard, but the industry is moving toward making it the standard."
