Abstract
1639
Objectives: Respiratory motion artifacts frequently confound clinical PET imaging of the thorax, as patient compliance and reproducibility remain a challenge. However, in animal studies with anesthesia and controlled ventilation, a high degree of reproducibility may be expected. A MicroPET acquisition protocol that gates on the inspiratory pause of the breathing cycle is proposed, thereby eliminating the effects of respiratory motion, while minimizing the amount of data that is rejected through gating. Such a protocol could significantly enhance the study of primate models of lung disease (e.g., tuberculosis, pneumocystis).
Methods: An anesthetized cynomolgus monkey (7kg) was injected with ~2 mCi of FDG and ventilated at 10 breaths per minute with a 30% inspiratory pause. The gating signal was generated using a pressure transducer, and the acquired data histogrammed into ten respiratory gates.
Results: Three adjacent gates were identified as corresponding to the period of inspiratory pause, with no indication of relative motion between the images. These gates comprise 30% of the total acquired data. Images without gating showed severe artifacts due to respiratory motion. Individual reconstructed gates showed little or no motion, though the image noise was much higher due to the poorer statistics. Combining the gates corresponding to the period of plateau resulted in images without motion artifacts and with less noise than the individual gated images.
Conclusions: Using respiratory gating together with an inspiratory pause allows for motion-free images to be obtained while retaining as much of the original data as possible. These images correspond to a well defined inspiratory state, and can readily be registered with other images obtained with the same degree of inflation.
- Society of Nuclear Medicine, Inc.