GE strengthens nuclear medicine linewith new variable-angle gamma camera

Clinical roles for solid-state camera examined

The nuclear medicine unit of GE Medical Systems made its biggestsplash in recent years at the Society of Nuclear Medicine meetingthis month, with the launch of dual-head variable-angle cameratechnology, improvements in acquisition and display software,and clinical images that demonstrated progress for its solid-statecamera design.

The dual-head Millennium MG, shown as a work-in-progress atthe Denver meeting, will transport GE into the true variable-angledual-head market for the first time. The heads adjust from 101°to 180° to gain maximum sensitivity close to the collimators,while reducing the dead space normally associated with variable-headcameras, according to James Shepard, general manager of GE's globalnuclear and PET business.

With a gantry footprint of roughly 20 square feet, MG is themost compact camera in its class, Shepard said. It is equippedwith two DigitalCSE detectors employing a new summation techniqueto generate additional diagnostic information from distant, smallsignals that are not processed by traditional Anger cameras.

The single-head rectangular Millennium MPR scanner, a work-in-progressat last year's Radiological Society of North America show, isnow a commercial product. The ring gantry is equipped with thesame DigitalCSE detector featured on MG. The table rises to gurneyheight or lowers to knee level for patients in wheelchairs. Thescanner plugs into a standard 110-volt wall outlet.

GE has retired the Starcam computer system in favor of a newGenie acquisition platform. The change creates an upgrade pathfor its Optima 90° dual-head customers to Optima NX, whichfeatures the Genie computer system. Attenuation correction forOptima is a work-in-progress. A commercial launch is planned laterthis year.

The new PC-based Genie acquisition system employs the sameauto-tab filing system introduced with Genie image processingworkstations two years ago. Auto-tab gives users simultaneousaccess to patient data, energy information, termination requirements,and image statistics needed to set up a study. Instant onlinehelp from Sherlock, an interactive training software program,was featured in GE's booth.

The company showed coincidence and collimation approaches tohigh-energy SPECT. Shepard envisions potential clinical rolesfor both techniques. Collimated high-energy imaging appears applicablefor cardiac and possibly brain imaging, he said, while coincidenceimaging has a potential role in oncological applications.

GE showed clinical images acquired with the coincidence imagingtechnique on its dual-head Maxxus. But with a hugeinvestment inpositron emission tomography (PET), GE officials were understandablycircumspect about the potential of FDG imaging with modified gammacameras.

GE's solid-state camera technology may be several years awayfrom commercial reality, but the company gave the prototype cameraheadline treatment to show it is a serious contender in this field.

With partners eV Products, a division of II-VI in Pittsburgh,and Isorad in Israel, GE last year announced development effortson a solid-state gamma camera based on cadmium zinc telluridedetectors that convert gamma rays directly into electrical signals(SCAN 7/6/95). The 16 x 16-cm CZT flat-plate detector comprisessolid-state material attached to preamplifiers. The resolutionis equivalent to standard Anger cameras, according to Shepard.Details regarding the specific configuration were not released.

The detector is connected to a flexible cable, which in turnis attached to a combined image display and central processingunit. The entire system is similar in size and weight to a standardultrasound scanner. It is mounted on wheels for movement aroundthe hospital.

Although the camera is not yet capable of SPECT imaging, thedevelopers have met all system requirements needed for a deliverableproduct, Shepard said. Clinical images acquired with a prototypecamera were presented, including planar cardiac studies and thyroidand pediatric kidney images.

Several issues concerning CZT crystal production must be addressed,however. The partners have to find a way to manufacture largequantities of CZT inexpensively before GE can introduce a commercialproduct, Shepard said.

"We have to increase the yields of our material so thatwe get to the point where we are going into a second-generationprototype camera," he said.

For extra emphasis, GE presented an industrial design mockup.It was equipped with a working 13-inch liquid-crystal flat-paneldisplay. The monitor presented 1280 x 1024-resolution images drawnfrom a standard GE Genie workstation.

GE also elaborated on possible clinical applications for thelightweight configuration. The heart function of a patient withchest pain could be examined with the scanner in the emergencyroom, or the detector could be positioned against the chest ofa patient in a wheelchair in an outpatient department, Shepardsaid. GE engineers are developing detachable heads for the scanners,similar in concept to transducers used in diagnostic ultrasound.The company displayed a fingertip-type intraoperative probe, forexample, that eventually may find a role in surgical settings.