Quantitative imaging with PET requires accurate measurements of the amount of radioactivity injected into the patient and the concentration of radioactivity in a given region. Recently, new positron emitters, such as 124I, 89Zr, 82Rb, 68Ga, and 64Cu, have emerged to promote PET development, but standards are still largely lacking. Therefore, we propose to validate a simple, robust, and replicable methodology, not requiring the use of any standards, to accurately calibrate a dose-calibrator for any β+-emitter. On the basis of 18F cross-calibration, routinely performed with fluorine-18-fluorodeoxyglucose (18F-FDG) in nuclear medicine departments, a methodology was developed using β+-emitting’ phantoms to cross-calibrate the dose-calibrator for measuring the activity of positron emitters and quantifying the standardized uptake value (SUV). 68Ga phantoms filled with activities measured with various dose-calibrator settings were imaged to establish calibration curves (SUV values as a function of the dose-calibrator settings) and to identify the setting value, yielding an SUV value of 1.00 g/ml, reflecting an accurate measurement of 68Ga activity. Activities measured with the identified setting were finally checked with a γ-counter. The setting of 772±1 was identified as ensuring that the studied dose-calibrator is correctly calibrated for 68Ga to ensure an SUV value of 1.00±0.01 g/ml. γ-Ray spectrometry confirmed the accurate measurement of 68Ga activities by the dose-calibrator (relative error of 2.9±1.5%). We have developed a phantom-based method to accurately standardize dose-calibrators for any β+-emitter, without any standards.
aBordeaux University Hospital Center, Nuclear Medicine Department, Haut-Levêque Hospital
bUniversity of Bordeaux, INCIA, UMR 5287
cCNRS, INCIA, UMR 5287, Bordeaux, France
Correspondence to Clément Morgat, PharmD, Bordeaux University Hospital Center, Haut-Levêque Hospital, Avenue de Magellan, 33600 Pessac, Bordeaux, France Tel: +33 5 57 65 64 08; fax: +33 5 57 65 68 39; e-mail: email@example.com
Received August 8, 2014
Accepted September 11, 2014