TLC scanner checks beta-emitting radionuclide purity

The Queen Elisabeth Hospital in Birmingham, UK, is using a TLC scanner and software from LabLogic Systems to check the purity of Yttrium-90 Zevalin, the cancer therapy for non-Hodgkin's lymphoma.

Zevalin is prepared from a radiopharmaceutical kit on the day of administration, and the manufacturer specifies that before the dose is administered thin-layer chromatography (TLC) must be used to confirm its radiochemical purity as 95% or more.

Although the Queen Elisabeth's radiopharmacy already had TLC facilities, they were designed – like those of many hospitals – for measuring the more commonly used gamma-emitting radionuclides rather than the pure beta-emitting Yttrium-90 in Zevalin.

The hospital found the beta detection capability it needed in the Mini-Scan TLC scanner and Laura radio-chromatography data collection and analysis software, both from LabLogic Systems.

Lindsey Halliburton, the hospital's specialist urology radiopharmacist, reports that the system began to show a return on investment immediately. "We went live with the Mini-Scan when we were preparing the dose for our first Zevalin patient," she says. "We knew it met the purity standard as soon as the chromatogram was being scanned, and then Laura confirmed it.

"Without the LabLogic system we would have had to do more complex dilutions to get accurate counts that would then have to be interpreted via a spreadsheet, adding time to the process while the patient was waiting for the preparation.

"The Mini Scan had already won our confidence during our initial trials, because it gave us accurate results that we felt were much more trustworthy than the conventional cut and count method."

Determining purity is especially critical in the case of Zevalin which, at around US$24,000 on average, is currently the world's most expensive single-dose drug. It justifies its high cost because it is effectively a complete course of lymphoma therapy delivered in just 7-9 days - one visit for imaging, another for a gamma scan, and the third for the dose itself.