New Scanner Captures 3D Image of Entire Human Body at Once

This spring, researchers at the University of California, Davis (UCD), anticipate a roll-out of the EXPLORER PET/CT scanner, described as the world’s first medical imaging system that can capture a 3D image of the entire human body simultaneously.

Unveiled in November 2018, EXPLORER can scan up to 40 times faster and use up to 40 times less radiation dose than current PET systems. Because it captures radiation more efficiently than other scanners, it can produce an image in as little as one second and can produce a diagnostic scan of the whole body in as little as 20 seconds.

Human scans using EXPLORER PET/CT scanner, courtesy of UC Davis and Zhongshan Hospital.

With further research, it is projected that EXPLORER will also be able to create movies that track radiolabeled drugs as they move around the body. Reduced scanning time could also improve image quality, because there would be far less patient motion.

In a subgroup of patients initially believed to have a high probability of malignancy, the use of CEUS showed 78% of the tumors were not malignant. In another subgroup of patients thought to have a 100% chance of malignancy, 38.7% of the kidney masses were found to be nonmalignant.

Following successful testing of the scanner last year, the goal is to have the system up and running at the EXPLORER Imaging Center in Sacramento by June 2019. Developed at the UCD biomedical engineering department, in collaboration with Shanghaibased United Imaging Healthcare, the technology was conceived 13 years ago by Simon Cherry, distinguished professor in the UCD department of biomedical engineering, and Ramsey Badawi, chief of nuclear medicine at UCD Health and vice-chair for research in the department of radiology. The project was launched with a $1.5-million grant from the National Cancer Institute in 2011. The first working model was made possible by a $15.5-million grant from the National Institutes of Health in 2015.

“The level of detail was astonishing, especially once we got the reconstruction method a bit more optimized. We could see features that you just don’t see on regular PET scans,” Badawi said in an interview with UCD Health.

“And the dynamic sequence showing the radiotracer moving around the body in three dimensions over time was, frankly, mind-blowing. There is no other device that can obtain data like this in humans, so this is truly novel,” Badawi added.

Other capabilities of the EXPLORER system include making it possible to conduct repeated studies in an individual and dramatically reducing the radiation dose in pediatric studies. The system can also allow practitioners to see what is happening simultaneously in multiple areas of the body. For example, it could quantitatively measure blood flow or show how the whole body takes up glucose. Researchers further envision being able to use the system to study cancer that has spread beyond a single tumor site, as well as inflammation, infection, and immunological, or metabolic disorders. In addition, the system can be used for research in systems medicine, including endocrine and immunological signaling related to the brain-gut and hypothalamus-pituitary-adrenal axes, which are implicated in a range of debilitating disorders, including irritable bowel syndrome. 

In current whole-body PET scans, roughly 85–90% of the body is outside the FOV of the scanner, thus no signal is collected from those regions of the body. Even for those regions inside the scanner FOV, no more than 5% of the available signal can be collected because the radiation is emitted isotopically and most of it does not intercept the detector rings. EXPLORER was designed to address these limitations by extending the detector rings to cover the entire body, a concept called total-body PET, to allow maximal detection of the radiation emitted from the body.

“While I had imagined what the images would look like for years, nothing prepared me for the incredible detail we could see on that first scan,” Cherry stated. 

“The tradeoff between image quality, acquisition time, and injected radiation dose will vary for different applications, but in all cases we can scan better, faster, with less radiation dose, or some combination of these,” Cherry said.

“I don’t think it will be long before we see a number of EXPLORER systems around the world,” he continued. “But that depends on demonstrating the benefits of the system, both clinically and for research.”

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