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Erschienen in:
01.05.2011 | Original Article
Effect of the positron range of 18F, 68Ga and 124I on PET/CT in lung-equivalent materials
Erschienen in: European Journal of Nuclear Medicine and Molecular Imaging | Ausgabe 5/2011
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Purpose
The aim of this study was to investigate the effect of positron range on visualization and quantification in 18F, 68Ga and 124I positron emission tomography (PET)/CT of lung-like tissue.
Methods
Different sources were measured in air, in lung-equivalent foams and in water, using a clinical PET/CT and a microPET system. Intensity profiles and curves with the cumulative number of annihilations were derived and numerically characterized.
Results
68Ga and 124I gave similar results. Their intensity profiles in lung-like foam had a peak similar to that for 18F, and tails of very low intensity, but extending over distances of centimetres and containing a large fraction of all annihilations. For 90% recovery, volumes of interest with diameters up to 50 mm were required, and recovery within the 10% intensity isocontour was as low as 30%. In contrast, tailing was minor for 18F.
Conclusion
Lung lesions containing 18F, 68Ga or 124I will be visualized similarly, and at least as sharp as in soft tissue. Nevertheless, for quantification of 68Ga and 124I large volumes of interest are needed for complete activity recovery. For clinical studies containing noise and background, new quantification approaches may have to be developed.