Counting positrons from PET radio-pharmaceuticals

With half-lives of just 20.4 and 110 minutes respectively, the beta+ emitters 11C and 18F must be produced and administered - and their metabolites identified - in the fastest possible time.

The Posi-Ram coincidence counter from LabLogic Systems has been developed specifically for the low-level beta+ counting necessary for studying the metabolism of the novel radio-pharmaceuticals now being used in PET medicine.

With half-lives of just 20.4 and 110 minutes respectively, the beta+ emitters 11C and 18F must be produced and administered - and their metabolites identified - in the fastest possible time.

The Posi-Ram meets the last of those requirements using the same electronics platform as employed in the company's Beta-Ram on-line radio HPLC flow-through detector.

It has a flat, thin-wall cell coil sandwiched between two opposed 1x1inch BGO crystal photomultiplier assemblies at a separation of <0.2inch - a configuration that creates a good geometric efficiency for collecting the annihilation gammas generated by the positron labels.

At the same time, backgrounds are inherently low.

Only coincidences are recorded, while PMT noise and conventional gamma counter backgrounds are rejected.

The Posi-Ram is a complete counter suitable for gamma measurement as well as positrons.

It has two counting channels and a digital display, and a built-in collector valve at the cell exit responds to manual or automatic control.

There are digital and analogue outputs.

LabLogic's Laura 3 software is available to perform decay correction, to find and integrate peaks automatically, and to control fraction collectors and auto-injectors.

GLP compliance is facilitated by a multi-level, user-defined security system and a comprehensive audit trail that generates accurate and complete copies of records in both human-readable and electronic form.

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