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Influence of radiation source geometry on determination of 111In and 90Y activity of radiopharmaceuticals

Peitl, Petra Kolenca; Tomse, Petraa; Kroselj, Markoa; Socan, Aljaza; Hojker, Sergeja; Pecar, Slavkob; Stopar, Tanja Gmeinera

Nuclear Medicine Communications: October 2009 - Volume 30 - Issue 10 - p 807-814
doi: 10.1097/MNM.0b013e32832fd0ea
ORIGINAL ARTICLES
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Objective Yttrium-90 (90Y)-labelled peptides such as DOTATOC and antibodies such as Zevalin are widely used in radionuclide therapy. Indium-111 (111In) is used as a 90Y surrogate for imaging and dosimetry purposes. We aimed to investigate accuracy, geometry (vials and syringes) and volume dependencies for both radionuclides in several different radionuclide calibrators.

Methods 90YCl3 and 111InCl3 solutions were gravimetrically dispensed into the most frequently used containers. In each container several dilutions of the parent solutions were performed. Mass, activity and time were recorded for each calibrator and measurement. Aliquots of both parent solutions were calibrated at the National Metrology Laboratory, Vienna, Austria (BEV). From our measurements and results from BEV, correction factors were determined and further partitioned into calibration, geometry and volume correction factors.

Results Using the nominal calibration factors provided by the manufacturer, measured activity in P6 vials was overestimated by up to 25% for 111In, depending on the calibrator. 90Y activity was either underestimated (by up to 20%) or overestimated (by up to 25%) using different radionuclide calibrators. This is the result of the difference in containers used to set the manufacturer's calibration factor values and the containers used in nuclear medicine departments and in this study. There was little geometry dependence for glass vials but strong geometry dependence for syringes for both radionuclides in all calibrators.

Conclusion The results should constitute a warning for all personnel responsible for preparation of radiopharmaceuticals. Every nuclear medicine department should incorporate a proper quality-control regimen for radionuclide calibrators and a quality-assurance system.

aDepartment for Nuclear Medicine, University Medical Centre Ljubljana, Zaloska

bUniversity of Ljubljana, Faculty of Pharmacy, Askerceva, Ljubljana, Slovenia

Correspondence to Petra Kolenc Peitl, University Medical Centre Ljubljana, Department for Nuclear Medicine, Zaloska 7, 1000 Ljubljana, Slovenia

Tel: +386 4 180 54 47; fax: +386 1 522 22 37; e-mail: petra.peitl@kclj.si

Received 6 March 2009 Revised and Accepted 16 June 2009

© 2009 Lippincott Williams & Wilkins, Inc.