Nuclear camera alters Anger method

Iain Stark, former president of the North American subsidiaryof Scottish gamma camera manufacturer Scintronix (SCAN 12/28/88),has invented an innovative "non-Anger" nuclear medicinecamera. Stark lined up Canadian venture capital last year to supportcommercialization of the product.

The patent-pending camera converts analog image data (the lightproduced by the scintillation crystal) to digital form withinthe camera's photomultiplier tubes. Analog to digital conversionin the PM tubes has been explored in the past, but handling themassive amount of digital data produced in the process proveddifficult, Stark told SCAN.

Stark has found a way to process up to 300 megabytes of digitaldata per second rapidly enough to determine a position for eachnuclear event and provide a sufficiently high count rate. Thekey is not raw computer power, he said. Although Stark's prototypedoes have seven computers to guide signal processing, gantry movementand postacquisition processing, these computers are not outlandishlyfast, he said.

"No computer can handle 300 megabytes a second, let alonedo the calculations on an event-by-event basis. That is the problem.That is why other people haven't done it," Stark said.

Stark founded and is president of Independent ScintillationImaging Systems (ISIS) of Montreal. ISIS attended the Societyof Nuclear Medicine meeting last month to introduce its system,although the firm was not able to bring the prototype to the exhibitfloor.

ISIS has not yet signed on a partner to help sell the system.A number of parties expressed interest at the SNM show, and thefirm plans to develop its commercialization strategy over thenext two months, Stark said.

Stark's technology overcomes several fundamental problems linkedto the image formation process in scintillation cameras that havebeen in use since H. O. Anger proposed the concept in 1957. Theprinciple of the Anger camera is flawed in a way that requirescomplicated linearity and energy correction as well as thresholdpreamplifiers that cut off the information from distant PM tubes,he said.

"The advantages of having solved the problem (of handlingdigital data from the PM tubes) are tremendous. You have betterpositional resolution, energy resolution and linearity. You obtaina bigger field-of-view out of the same crystal, and you are ableto image off-peak in a way other cameras cannot," Stark said.

Patents have also been filed on the camera's mechanical system.The unit automatically changes collimators and can be programmedto run quality assurance tests prior to each day's use, he said.

The camera's gantry can perform circular and noncircular SPECTprocedures, including body contouring, without having to movethe patient bed. Setup for contour exams is rapid since the bedis stationary and its coordinates are programmed into the computer'sguidance system.

"The camera can synthesize any motion in a completelyindependent way. Since the bed height is fixed, the only variabilityis how deep the patient is. When you drive the camera down untilit touches the patient, it (the computer) knows all the parameters.Setup for SPECT takes eight to ten seconds," Stark said.