Fractionated elution of 99Mo/99mTc generators using calibrated vials

Fractionated elution consists in collecting the fractions of an eluate with the highest radioactive concentration. It may be useful to meet the requirements of a subset of clinical radiopharmacy procedures. This study aims to describe and evaluate straightforward procedures allowing to readily perform fractionated elution on dry and wet columns Mo/Tc generators by using calibrated vials. The main objectives of this study consisted in determining the relationship between eluate volume and elution yield using different vials calibration and assessing repeatability of the procedure. Elution vials were calibrated to obtain different eluate volumes by addition of air for wet column generator (WCG) and subtraction of saline for dry column generator (DCG) (n≥5 for each calibration). The relationship between the eluate volume and the elution yield was determined by a regression model for both DCG and WCG. Then repeatability evaluation was performed using 3-ml vial calibration. Relationships between the eluate volume (V) and the elution yield (Y) for DCG and WCG were Y=57.551 ln(V)+10.526 and Y=50.256 ln(V)+17.597, respectively. For repeatability assessment (n=30 for DCG and n=31 for WCG), the median volume and the interquartile range for DCG and WCG were 2.98 ml (2.92-3.01) and 3.28 ml (2.71-3.40), respectively, and median (interquartile range) eluate yields were 84.73% (81.30-86.33) and 81.78% (78.91-85.20), respectively. The volume was significantly higher for WCG than DCG (P=0.036) and also significantly more variable (P<0.001). The elution yield was significantly lower for WCG than DCG (P=0.025), but no difference in variability between the two generators was found (P=0.874). Easy-to-handle fractionated elution methods are compatible with both DCG and WCG. Fractionation using calibrated vials exhibits a better reproducibility with DCG than WCG generators and represents the only proposed method so far to master fractionated elution with DCG.