Picker joins ADAC in club of vendorswith coincidence-detection clearance

Company ramped up work due to clinical interest

ADAC Laboratories may claim to be the leader in high-energy coincidence-detectionimaging, but it can no longer claim to be the only company ableto market a product using this promising new nuclear medicinetechnology. Picker International received Food and Drug Administration510(k) clearance for its Positron Coincidence Detection (PCD)technique last month, only a year after starting a crash programto catch up with ADAC's work in the modality.

ADAC took the nuclear medicine market by surprise last yearwhen it received clearance for Molecular Coincidence Detectionless than six months after debuting the technology at the Societyof Nuclear Medicine meeting in Minneapolis (SCAN 12/13/95 and6/21/95). Coincidence detection enables standard SPECT camerasto image fluorodeoxyglucose, which is usually imaged with costlyPET cameras.

Picker was not caught completely off-guard, however. The companyhad conducted early work in coincidence detection some years ago,but had put the work on the back burner due to concerns aboutavailability of FDG, according to marketing manager Josh Gurewitz.

Picker ramped up its program when it saw the amount of clinicalinterest MCD was receiving. Picker showed early work at last year'sRadiological Society of North America meeting, and had clinicalimages at this year's SNM conference (SCAN 7/3/96).

The beauty of coincidence detection is that it gives nuclearmedicine physicians the ability to gain the metabolic informationavailable through PET imaging without the high cost of a PET camera.The technology holds the promise of revitalizing the sluggishgamma-camera market, which, since the arrival of SPECT in the1980s, has been awaiting a breakthrough new technology to spurpurchasing.

PET proponents are wary of coincidence detection, however,concerned that it may cannibalize their long-suffering market.Interestingly, neither ADAC nor Picker, the only companies withFDA-cleared coincidence-detection products, markets PET cameras.

There are some drawbacks to coincidence detection in comparisonto PET, most notably in the count rates of the respective systems.Since the SNM meeting, Picker has made headway in boosting thecount rate of gamma cameras using PCD to approximately one millionsingles counts per second (the singles count rate is the standardcount rate of gamma cameras when not in coincidence mode, whichdiscards single annihilation events in favor of coincident events).

Still, the coincidence count rate most clinicians are experiencingis about 10,000 to 15,000 counts per second, far less than a PETcamera's 200,000 counts per second. The lower rate means thatcoincidence-detection studies will take much longer than PET scans,though not much longer than a standard nuclear medicine SPECTstudy, Gurewitz said. In any event, Picker believes the PCD imagesare clinically useful.

PCD's resolution is about 4.5 mm, compared with above 4 mmfor PET cameras. Despite recent advances, there is still a noticeabledifference in image quality between a SPECT camera in coincidencemode and a PET camera, Gurewitz said. SPECT cameras may closethe gap as gamma-camera detector electronics improve, however.

PCD is designed for Picker's dual-head Prism 2000 XP gammacameras, and may be adapted for the Prism 3000 XP system, dependingon clinician interest in triple-head coincidence detection. TheCleveland vendor plans to begin placing PCD at beta sites in thenext several weeks, with commercial shipments slotted for earlynext year. Picker will offer PCD in two versions: one with a standard3/8-inch crystal and another with a thicker crystal for highercount rates.

Coincidence detection collects massive amounts of data, butPicker has dealt with that problem through a new version of itsOdyssey nuclear medicine workstation. Odyssey FX succeeds OdysseyVP and employs new Digital Equipment Alpha microprocessors. OdysseyFX is available in three configurations, each based on Alpha chipsthat carry SPECint95 ratings of 380, 451, and 729, respectively.

Like other nuclear medicine executives, Gurewitz hopes thatPCD, and other coincidence-detection techniques, will providethe spark that will help the gamma-camera market rebound fromits long slump.

"The interest in being able to do coincidence detectionhas started some incremental demand for systems that may not havebeen there prior to this," Gurewitz said. "All the manufacturersare hoping that the dual-head segment of the gamma-camera marketwill see an upturn because of this."

In other Picker nuclear medicine news, the vendor won 510(k)clearance last month for its simultaneous transmission -emissionprotocol attenuation correction technique for Prism 2000 XP. Pickerwill use the clearance to investigate oncology applications ofSTEP with the opposing dual-head camera.