A $15+ million effort to develop the world’s first total-body PET scanner is one of several UC Davis efforts to improve imaging efficacy and safety for cancer and other conditions


Clinicians have a choice of scanners to diagnose what ails us, but not all are alike. Unlike CT, MRI, X-rays and other imaging techniques that help us visualize bodily structures, positron emission tomography or PET can tell us what cells in the body are actually doing.

This can be extremely useful. PET scans are widely used to diagnose and track a variety of diseases, including cancer, because they show how organs and tissues are functioning and can see tumors as glowing bright spots.

PET can also be used as a tool in the development of new drugs, helping to determine early in the research process whether they go where they’re intended or drift elsewhere to cause toxic side effects.

While PET has been around for decades, it still has shortcomings that keep it from fulfilling its potential. But perhaps not for long. Simon Cherry, distinguished professor in the Department of Biomedical Engineering, in collaboration with Ramsey Badawi, chief of the Division of Nuclear Medicine, is working with colleagues at UC Davis and beyond to improve PET technology and provide faster, clearer scans using less radiation.

A team led by Cherry and Badawi was recently awarded $15.5 million to build the world’s first total-body PET scanner, which could fundamentally change the way cancer and other diseases are diagnosed and tracked and put the university on the nation’s leading edge of molecular imaging research and practice.

The Transformative Research Award, part of the National Institutes of Health High-Risk, High-Reward Program, supports bold and untested ideas that have the potential to be paradigm shifting. The five-year grant will be administered by the National Cancer Institute and funds the UC Davis-led EXPLORER project, which also involves University of Pennsylvania and Lawrence Berkeley National Laboratory researchers.

“The vision of the EXPLORER project is to solve two fundamental limitations of PET as it is currently practiced,” said Cherry, who directs the UC Davis Center for Molecular and Genomic Imaging, co-leads the UC Davis Comprehensive Cancer Center’s Biomedical Technology Program and in February was elected to the National Academy of Engineering. “The first is to allow us to see the entire body all at once. The second huge advantage is that we’re collecting almost all of the available signal, which means we can acquire the images much faster or at a much lower radiation dose.

“That’s going to have some profound implications for how we use PET scanning in medicine and medical science.”

Speed and safety

In the case of a total-body PET, the increase in the signal collected can mean dramatic improvements in speed and safety. Standard PET machines can only see the body in 20-centimeter chunks, which amounts to about 8 inches. To image the entire body, clinicians have to “step” it through one chunk at a time.

“By developing a scanner that covers the entire body, allowing us to see the radioactively labeled molecules we have given the patient in all organs simultaneously, we can either drop the radiation dose by a factor of 40 or image 40 times faster,” Cherry said. “Rather than a scan taking 20 minutes, it could take just 30 seconds.”

The reduced radiation dose (roughly equivalent to that received from a round trip flight from the west coast to Europe) could benefit pediatric and other patients who might be more sensitive to radiation. It could be particularly helpful for patients who require several scans to track disease progression or determine if a treatment is working. In addition, capturing scans much more quickly could mean images will be less blurred by movement of the patient, allowing physicians to get a clearer view of smaller tumors or other early signs of disease.

Total-body PET scanners could also better track how far metastatic cancer has spread, monitor how patients are responding to treatment, or clarify how immunotherapy activates the body’s ability to attack cancer.

“This scanner could help with anything that’s a whole-body phenomenon,” Cherry said. “Think inflammation, infection, immune and cell-based therapies, and development of new drugs.”

The advantages of a bigger PET scanner are obvious, but have not yet come to fruition because the technological challenges are quite daunting. For example, a larger scanner means handling huge amounts of data.

To overcome this and other issues that prevent PET scanning from reaching its full potential, Cherry’s team is collaborating with multiple researchers and companies around the world to develop better data-tracking technology and improve sensors.

Research benefits

Though direct patient care is the ultimate goal for a full-body PET, it’s expected that research applications could provide the greatest benefits in the near future.

“There are many questions that we couldn’t possibly ask before – and now we will be able to ask them,” Badawi said. “This is not just a big instrumentation grant. It’s going to give us a tool that will allow us to see things we’ve never seen before.”

The scanner could follow a drug’s path through the body, helping pharmaceutical and biotech companies determine if an agent is hitting its target and whether it’s sequestered in the heart, liver or kidneys– a potential warning sign for toxicity.

The information could give medicinal chemists and pharmacologists early opportunities to redesign a molecule – or try another compound entirely – to avoid toxicity and move potentially life-saving drugs down the pipeline. This possibility is already intriguing drug companies interested in the early prototype being developed by Cherry and Badawi’s team.

Fundamental research for the project was made possible by the UC Davis Research Investments in the Sciences and Engineering program, designed to launch large-scale interdisciplinary research activity at UC Davis.