A. Martinez-Möller, W. Howe, M. Schwaiger, S. Nekolla Motion Free Images by Dual Gating of PET Listmode Acquisitions World Congress of Cardiology, held in Barcelona, Spain, September 2006 (bib)
	Cardiac and respiratory motion decrease PET image quality by reducing the observed spatial resolution. Whereas cardiac motion has been corrected using ECG gated acquisitions, respiratory motion is still an unsolved issue. In this work we prove the feasibility of dual gated acquisitions in a clinical setup. The resulting images are evaluated to assess the extent of the respiratory motion. Methods: The ECG and respiratory signals of the patients were recorded synchronized to the listmode acquisition. The listmode events were sorted according to the cardiac and respiratory phases, and the sinograms were reconstructed into corresponding dual gated images. 12 heart scans were acquired with a Siemens Biograph16 PET/CT, the systolic component of the heart cycle was discarded and reconstructions with 4 and 8 respiratory gates were performed. The respiratory motion of the heart in each of the cases was assessed. Results: Respiratory motion of the heart could be clearly observed on the gated PET images (see Fig 1). The average displacement of the apex between end inspiration and end expiration phases was 7.0±2.1 mm in the craniocaudal direction. Local motion was 5.6±1.0 mm in the inferior wall and 3.3±1.0 mm in the anterior wall, indicating that the heart has an elastic motion due to respiration. Conclusions: Dual gated studies were successfully performed with virtually no impact on the clinical workflow. The respiratory motion of the heart was in the same range as the thickness of the normal myocardial wall (7-13 mm) and its correction could improve the observed spatial resolution in myocardial PET. Dual gated acquisitions are particularly promising for hot spot cardiovascular imaging where the targeted structures are likely to be smaller than the motion itself.
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