By law, nuclear-imaging gamma cameras must be tested weekly to ensure that they are performing properly. But traditional tests, which measure the camera's ability to discern small objects and to position images correctly on film, can take 20 minutes or more per machine. Multiply a couple of cameras, some of them with two or three detector heads, by 52 tests each year and you have nuclear medicine-imaging facilities losing hundreds of hours that could be spent testing patients.

So the question is, how can quality-control tests be performed more quickly and efficiently without compromising their effectiveness?

Joseph W. Vilani, clinical assistant professor of nuclear medicine and a board-certified medical and health physicist, has come up with a solution: the UB Gamma Camera Test Pattern.

One-image testing

Traditional test patterns, composed of bar patterns of varying thicknesses, must be imaged four times, rotating the plate by quarter turns, in order to test all of the gamma camera's quadrants.

Vilani has redesigned the test pattern to enable technicians to perform the same tests in one image.

"The 20 or 30 minutes that it takes to test each camera could be the time it takes to see a patient. That's money that's being lost out of the department each time a camera is down for testing," Vilani said.

Considering there are as many as 6,000 cameras throughout the United State, the industry could be losing millions of dollars each year.

Vilani's test pattern, which is in the process of being patented, is being manufactured by Nuclear Associates, a company that specializes in the manufacture of accessories for radiology, nuclear medicine, radiation therapy and radiation protection.

The 20-by-20-inch test plate is made up of four frequencies of parallel-line, equally spaced bars that are a quarter of an inch, three-sixteenth of an inch, five-thirty-seconds of an inch and one-tenth of an inch in thickness and arranged in L-shaped configurations.

The test plate is constructed of Lexanª, the same plastic that is used in bank windows, because it can be machined precisely to create the plate's parallel channels. The channels are filled with Cerrobendª, a metal alloy composed of bismuth, lead, antimony and cadmium. This high-density alloy melts at the boiling point of water, which makes it easy to work with since, at that relatively low temperature, it will not warp the plastic test plate.

Prototype made at UB

The prototype for the test plate was manufactured in the Department of Nuclear Medicine's machine shop.

In routine quality-control testing, the shadows created by this unique test pattern are used to evaluate the gamma camera's spatial resolution-its ability to see small objects-and spatial linearity-its ability to correctly position image data.

According to Vilani, Nuclear Associates will produce an initial lot of 100 of the UB Gamma Camera Test Pattern, which is expected to save the average nuclear-imaging facility thousands of dollars in down-time each year.

"I know of a clinic in town that wants to buy three now," he added.