From the June 2017 issue of HealthCare Business News magazine
Ramsey D. Badawi, professor and molecular imaging chair in radiology at the University of California, Davis, and chief of nuclear medicine, and Simon R. Cherry, Ph.D., a distinguished professor of biomedical engineering and radiology at UC, Davis, are two men with a single vision: to build a PET scanner large enough to image an entire human in a single scan. The mission to create this “whole body” PET scanner became their passion – and now they’re on the verge of seeing that vision come true. HealthCare Business News interviewed the two men so they could detail how they are meeting this challenge.
HCB News: How did this whole body PET project initially get started?
Badawi & Cherry:
In the fall of 2005, we were discussing future projects that we could collaborate on. I mentioned that I had done some simulations of long PET scanners in the past and that we should try to build one, perhaps 60 cm long or so. Simon replied that if we were to do this, we should go the whole hog and build a two-meter one that would cover the entire body! We both got very excited about this idea and decided to pursue it. We launched the project in 2006, when Simon described the idea at the Henry Wagner Jr. lecture at the SNMMI annual meeting. It took us 10 years from the time of the initial idea to finally obtaining funding from the NIH to build the first prototype.
HCB News: What are the perceived benefits from whole body PET compared to conventional PET imaging?
B & C:
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There are two main features that lead to a range of benefits: for total body applications, one can collect ~40x as much signal as with a conventional scanner (or about 5x more signal if one is only interested in a single organ) and one can scan the entire body simultaneously.
Due to the increased sensitivity to signal, one can either:
- Scan faster for the same image quality, reducing a 20-minute scan to perhaps 30 seconds and a single breath-hold. This should reduce the effects of motion blurring and allow many more patients to be scanned in the same amount of time. It also reduces the need for anesthesia in pediatric patients, which is a major plus.
- Scan better. We can use the extra signal collected to make much clearer images, allowing us to see smaller and more subtle changes due to disease, and to use more complex models to describe radiopharmaceutical behavior in the body.
- Scan longer. PET scans involve injecting a small amount of radioactive material (such as a sugar analog) and using the scanner to see where it goes. These materials decay with a certain half-life. The most commonly used materials decay with a roughly two-hour half-life, but some have a 75-second half-life and some have a three-day half-life. Current scanners can image for about ~3 half-lives before the signal gets too weak. EXPLORER should be able to scan for ~eight half-lives. This is very exciting and has not been attempted before. What will we learn about the human body when we can scan so long after injection of the radioactive material? We don't know yet.