Picker rewrites gamma camera design with variable-angle triple-head debut

SNM introduction may spell trouble for dual-head market

Nuclear medicine vendor Picker International hopes to revive the moribund market for triple-head gamma cameras with a radically redesigned triple-head system that may unlock the potential of the pricey cameras. Picker plans to unveil a new variable-angle triple-head gamma camera at next week's Society of Nuclear Medicine meeting in San Antonio.

Picker's new Irix triple-head is one of a brace of new gamma camera introductions the Cleveland vendor will make at the SNM meeting. Picker's other new system, Axis, is the company's first variable-angle dual-head camera, and can be upgraded in the field to a triple-head, the first such design in nuclear medicine.

Picker has been one of the few nuclear medicine vendors to continue offering a triple-head system, the fixed-angle Prism 3000XP. Siemens offers a triple-head camera, as does Toshiba, albeit only to the Japanese market. Trionix, another triple-head vendor, has run into financial difficulties lately, due to the collapse of its core market.

The triple-head segment has wilted in the last several years in the face of competition from variable-angle dual-heads, which are capable of conducting faster cardiac imaging studies when in the 90 configuration. Another disadvantage of triple-heads is that most cannot conduct whole-body bone scans.

Cardiac imaging studies make up 40% of nuclear medicine procedural volume, according to Picker, while whole-body bone scans make up another 40%, locking fixed-angle triple-head cameras out of 80% of the market. Fixed triple-head cameras have also suffered as a result of the small fields-of-view found on the systems, according to Josh Gurewitz, marketing manager in Picker's nuclear medicine division. While triple-head cameras have found a niche in brain imaging, procedural volume in that segment has declined due to encroachment by other imaging modalities.

To overcome the flexibility limitations of triple-head cameras, Picker made a major effort to develop a new gantry design that would support variable-angle detectors on a triple-head. The company's effort was aided by improvements made to its nuclear medicine engineering operations, which included the installation of highly advanced computer-aided design (CAD) systems, according to Karl Kellar, product manager for cameras and detectors.

"We spent literally a year building the tools to make the tools," Kellar said. "We put in probably the most advanced CAD capability that's operating in the medical imaging industry."

That effort resulted in what Picker calls its Variable Tangential (VT) gantry and detector architecture, which provides the Irix and Axis cameras with new ways to contour patients by moving detector heads during acquisitions without moving the gantry or patient table.

For the dual-head Axis, VT enables the system to adjust to a 102 configuration, in addition to standard 90 and 180 configurations used on other variable-angle systems. The 102 architecture is useful because it allows Picker to eliminate the corner-gap problem found on dual-heads in the 90 position. The phenomenon results because no photon signals are collected in the area that the detectors abut.

New configurations. The application of VT technology on the triple-head Irix has even more impressive results, however. The camera can conduct studies with all three heads at 90 or 102; two heads in the 90 or 102 configuration and the third head at a 180 position; or two heads in the 180 position and the third positioned laterally. The multiple configurations are appropriate for cardiac, whole-body bone, and 360 SPECT scanning.

In addition, the VT architecture enables the triple-head's detectors to overlap each other when positioned in the classic triangle-shaped triple-head configuration, enabling users to achieve a tight triangle even though the system employs large-field-of-view 15 x 20-inch detectors. The wide variety of configurations means faster throughput and more versatility for Irix users compared with dual-head cameras, Gurewitz said.

"No system is going to be faster than a triple-head for doing noncardiac SPECT," Gurewitz said. "For cardiac SPECT, we'll be just as fast as a variable-angle dual."

Both Irix and Axis will support Positron Coincidence Detection (PCD), Picker's term for its high-energy coincidence detection technique, which will be available as an option as soon as the cameras begin shipping. Irix will immediately be able to conduct dual-head PCD studies, but Picker sees intriguing possibilities in triple-head PCD, as the camera's additional detector will boost its count rate. The low count rate of SPECT cameras in coincidence mode is a major factor inhibiting the sensitivity of SPECT-based positron imaging relative to PET systems. Picker plans to make triple-head coincidence detection a major emphasis of further research.

While Irix and Axis employ radically redesigned gantries, the detectors found on the systems are based on those used in Picker's existing Prism line, with upgraded electronics. These detectors use four 14-bit analog-to-digital converters to digitize signals rather than an ADC on each photomultiplier tube.

Picker's competitors may seize on the detector electronics of Irix and Axis as points of comparison, for a number of gamma camera vendors tout the advantages of an ADC on each PMT. Picker, however, believes that image quality and patient throughput should have the final word, and the technical specifications of its new systems are competitive with those of other digital cameras, Gurewitz said.

Picker has 510(k) clearance for both cameras and plans to ship the first beta units to hospitals in the Cleveland area this summer, with production deliveries beginning in October. The company has not yet released list prices for the systems. All of Picker's Prism cameras will remain in production, giving the vendor a broad product line.

While Axis will shore up Picker's position in the dominant dual-head market, the company believes that Irix will seize market share from variable-angle dual-head cameras, just as those systems have taken market share from the triple-head segment, according to Gurewitz.

"Where are we going to get the market from? We are going to steal it from the dual-head market," Gurewitz said. "We believe that (the triple-head) market is going to get rebuilt by people who are currently looking at dual-head variables, and who will realize that there are significant advantages to going with a triple-head variable from a throughput and flexibility standpoint."