A series of PET studies using phantoms is presented to characterize the imaging and quantitative performance of the positron-emitting iodine isotope 124 I. Measurements were performed on the 2D-PET scanner GE 4096+ as well as on the Siemens PET scanner HR+ operated in both 2D and 3D modes. No specific correction was applied for the g-rays emitted together with the positrons. As compared to 18 F, in studies with 124 I there is a small loss of image resolution and contrast, and an increase in background. The quantitative results varied between different scanners and various acquisition as well as reconstruction modes, with an average relative difference of À6713% (mean7SD) in respect of the phantom radioactivity as measured with g-ray spectroscopy. We conclude that quantitation of a radiopharmaceutical labelled with 124 I is feasible and may be improved by the development of specific corrections. r

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Recently published methods for motion correction in neurological PET include the multiple acquisition frame (MAF) and LOR rebinning methods. The aim of the present work was to compare the accuracy of reconstructions obtained with these methods when multiple, arbitrary movements were applied to a Hoffman brain phantom during 3D list mode acquisition. A reflective target attached to the phantom enabled a Polaris optical motion tracking system to monitor the phantom position and orientation in the scanner coordinate frame. The motion information was used in the motion correction algorithms. The MAF method was applied to the list-mode data after sorting them into a series of dynamic frames, while the LOR rebinning method was applied directly to the list-mode data. A proportion of the list mode events had to be discarded during rebinning because the application of the corrective spatial transformation removed them from the 3D projection space. A correction for these 'lost' events was implemented as a global post-reconstruction scale factor, based on the overall fraction of lost events. Reconstructions from both motion correction methods were compared with a motion-free reference scan of the same phantom. Motion correction produced a marked improvement in image clarity and reduced errors with respect to the reference scan. LOR rebinning with global loss correction was found to be more accurate than the MAF method.

Maximal oxygen uptake is the major performance limiting factor in endurance sports. Sophisticated training methods have been developed to increase this variable. On the other hand, attempts have been made to improve maximal oxygen uptake by artificial means: blood doping and the misuse of recombinant human erythropoietin have beneficial effects on aerobic exercise capacity. Both methods have been banned by international sporting federations. A new class of substances might represent the next step of fraudulent improvement of the maximal oxygen uptake: artificial oxygen carriers, such as solutions based on recombinant, bovine or human hemoglobin and perfluorocarbon-emulsions have been shown to improve oxygen delivery to the muscle. Hemoglobin-based solutions improve aerobic exercise capacity in animal and human testing. Both substances have potentially lethal side effects including renal toxicity, increased systemic and pulmonary blood pressure and impairment of the immune system. Hemoglobin-based carriers can be detected in drug testing with routine laboratory tests based on the detection of free hemoglobin. Perfluorocarbon is not metabolized by the body and exhaled through the lung and can be measured with chromatography. No screening for these substances in drug tests has been performed so far. International sporting federations should be aware of this new, emerging doping threat.