Featured Research

from universities, journals, and other organizations

Texas Researchers Promise More Accurate PET Scans

Date:
September 26, 2001
Source:
Texas A&M University
Summary:
Tumors, seizure disorders and cardiac diseases are best detected at early stages with a technique called Positron Emission Tomography, but each PET scan costs about $2500 - until recently at the patient's personal expenses. Now PET scans have been approved for medical insurance reimbursement, and physicists at Texas A&M University and the University of Texas at Austin are working to improve PET scanners to make them even more accurate in the detection of abnormalities in human organs.

COLLEGE STATION, - Tumors, seizure disorders and cardiac diseases are best detected at early stages with a technique called Positron Emission Tomography, but each PET scan costs about $2500 - until recently at the patient's personal expenses.

Now PET scans have been approved for medical insurance reimbursement, and physicists at Texas A&M University and the University of Texas at Austin are working to improve PET scanners to make them even more accurate in the detection of abnormalities in human organs.

PET acts like a camera that produces images of an ailing organ by imaging radiation produced from energy related to the metabolic rate of the organ; the harder the organ works, the brighter the image.

"About 60 percent of these devices are used for brain research," says John A. McIntyre, a professor emeritus at Texas A&M who has been working on PET scans for the last 25 years. "Physicians inject glucose labeled with a radioactive chemical in the patient's body. The brain burns glucose, so the glucose goes to where the brain is working, and since the glucose produces radiation, the PET scan can image it. So it is a powerful way to look inside the brain."

A radiation-producing chemical emits particles called positrons. When a positron meets an electron from a nearby atom, the positron and the electron annihilate, creating two gamma rays moving in opposite directions.

"When scientists realized that the two gamma rays come out opposite to each other," McIntyre says, "they realized that if you could detect them, then somewhere on the line between them was the source."

To detect the pairs of gamma rays emitted by the radioactive source - and subsequently the damaged part of the brain - scientists surround the source with gamma ray detectors called scintillators.

"The instrument is a big ring," McIntyre says, "with slices inside the ring, just like inside a CAT (Computer-Assisted Tomography) scanner, each containing a scintillator.

"The challenge is to find out precisely where the source is," he adds. "When gamma rays have been detected in two opposite detectors in the ring, you draw a line between the detectors. Then you take another pair of detectors that have detected two other gamma rays, and you draw a second line. The source is at the intersection of these two lines."

Sharp pictures of the source depend on the size of the detectors. The larger the detector, the broader the reconstructed line and the fuzzier the picture.

"All you know is that the gamma ray hit the detector somewhere, but you do not know precisely where," McIntyre says, "so if you have a detector that is one centimeter across, the source of the gamma ray will always look one centimeter across. The width of the reconstructed point cannot be any smaller than the size of the detectors."

So McIntyre and his collaborators decided to make an instrument with more than one ring of detectors. They built a prototype with eight concentric rings of detectors so that, in addition to knowing the angular position of the gamma rays, they could also determine the gamma rays' radial positions.

The detectors in the radial direction are each tilted by a small angle so that each detector gives unambiguously the positions of eight points instead of one, enhancing the quality and sharpness of the picture.

To stop the gamma rays, high-density detectors are needed. Current PET scanners use crystal scintillators usually made of bismuth germanate oxide (BGO). Since McIntyre uses plastic scintillators which are one-eighth as dense as crystal scintillators, his device is radially eight times as thick as current PET scanners.

Plastic scintillators have many advantages over crystal scintillators: they are cheaper, they collect more light, and they collect it faster, McIntyre says. Indeed the ratio of the amount of collected light over the collection time is 480 times larger for a plastic scintillator than for a crystal scintillator, he adds.

"It is important to stop as many gamma rays as possible," says John Paulson, research associate of physics at the University of Texas at Austin, who recently finished his doctoral thesis on McIntyre's prototype and is now developing computer simulations to improve it. "These gamma rays provide the information for the image produced by the PET. And, the number of gamma rays available is limited by the amount of radioactivity that can safely be injected into the patient."

"We are now working on publishing all the results that we have," Paulson says. "New concepts are not accepted by the scientific community until they have passed the inspection of peer review and have been published in a scientific journal. After publications, the capabilities of the Texas A&M tomograph will be recognized."

Because of its cost (about $2 million), a PET scanner is usually affordable only for use in large medical centers. But PET scanners are also being shared by smaller hospitals. Trailer-mounted, they travel from one hospital to the next throughout one state and/or across neighboring states.

For example, a PET scanner is available at St. Joseph's Medical Center in Bryan, Texas, on Thursday of every other week. The scanner is mounted on a trailer and is traveling throughout Texas and Colorado.

"Cancer is the primary target of the scanner, but we also use it for brain disorders such as seizures" says Michael L. Wallin, nuclear medicine technologist at Radiation Corporation of America, the company operating the PET scanner.

The patient lies on a table that slides into the middle of the scanner. The scanner's electronics record the gamma rays produced by the scintillators and map an image of the area where the radioactive source is located.

"Once we get the patient positioned, we tell him or her just to relax, we turn down the lights, and we go in the control room where data are automatically processed in the computer," Wallin says. "The patient usually needs to lie still for 45 minutes to an hour."

It could take a few years before a PET scanner becomes available to more patients, time for McIntyre and Paulson to demonstrate the advantages of the novel design of the Texas A&M PET.


Story Source:

The above story is based on materials provided by Texas A&M University. Note: Materials may be edited for content and length.


Cite This Page:

Texas A&M University. "Texas Researchers Promise More Accurate PET Scans." ScienceDaily. ScienceDaily, 26 September 2001. <www.sciencedaily.com/releases/2001/09/010926071252.htm>.
Texas A&M University. (2001, September 26). Texas Researchers Promise More Accurate PET Scans. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2001/09/010926071252.htm
Texas A&M University. "Texas Researchers Promise More Accurate PET Scans." ScienceDaily. www.sciencedaily.com/releases/2001/09/010926071252.htm (accessed July 22, 2014).

Share This




More Matter & Energy News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins