Physicists Collaborate to Improve PET Scanning

Physicists are developing new electronics for identifying subatomic particles in high-energy accelerators that may also enable radiologists to detect cancer at an earlier, more curable stage.

"The electronics needs in medical imaging look very closely related to the needs we have in high-energy physics,” said Dr. Henry Frisch, professor of physics at the University of Chicago (IL, USA). "Physics tends to advance by new capabilities in measurement, the same in radiology.”

Radiologists, medical physicists, and high-energy physicists share a desire to measure more precisely the velocity and position of subatomic particles, according to Dr. Frisch. A considerable improvement in positron emission tomography (PET) technology could mean the difference between life and death for some patients, according to Dr. Chin-Tu Chen, associate professor in radiology at the University of Chicago. Being able to detect a tumor measuring a quarter of an inch in diameter rather than half an inch would mean starting treatment when the disease mass is eight times smaller by volume.

Drs. Frisch, Chen, and physicist Karen Byrum of Argonne [U.S.] National Laboratory (Argonne, IL, USA) are pursuing the joint effort with initial funding provided by the U.S. Department of Energy (DOE), Argonne, and the University of Chicago Cancer Research Center. Their project is part of an international scientific trend to apply high-energy physics technology to biomedical imaging techniques.

Whereas medical physicists look for disease, high-energy physicists try to identify what types of subatomic particles they generate in collider studies.

Current high-energy physics experiments typically measure particle velocities to within an accuracy of 100 picoseconds (a trillionth of a second). A photon can travel approximately one inch in 100 picoseconds. Dr. Frisch would like to increase the resolution to one picosecond.

In the PET environment, more accurate particle velocity measurements would mean improved image quality and therefore more accurate diagnoses, according to Dr. Chen. Achieving this would require an emerging technique called time-of-flight PET, which provides a positional measurement that conventional PET technology lacks.

In December 2006, the first commercial time-of-flight PET scanners become available. These scanners provide a time-of-flight resolution of 750 picoseconds, which corresponds to a resolution of a couple inches. "That's really not useful for improving the spatial resolution of PET,” said Dr. Chien-Min Kao, assistant professor in radiology at the University of Chicago.

Gathering of new time-of-flight data permits determination of signal locations in a direction at a right angle to the detector face as well. "If time-of-flight measurements can be assessed with an accuracy less than 30 picoseconds, better resolution in both directions can be achieved, essentially eliminating the need for complex and costly image reconstruction,” Dr. Chen said.


Related Links:
University of Chicago
Argonne [U.S.] National Laboratory