Abstract
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Objectives: The evaluation of different combinations of the binned data in double gated cardiac acquisitions in order to maximise the acquired data used in the reconstruction of motion free cardiac images.
Methods: A dynamic cardiac phantom study having different FDG concentrations in the myocardium, left ventricle and coronaries was used. PET data was acquired in list mode (LM), where both respiratory and cardiac motion triggers were registered. Subsequently data were binned considering 4 cardiac gates (1-3 in the systole and 4 in the diastole) in combination with a variable number of respiratory gates either in amplitude or phase. Each of the respiratory gates contained either the 3 cardiac bins over systole (50% of the cardiac cycle) or bin 4 over the diastole (representing the other 50% of the cardiac cycle). Reconstructed images from each of the respiratory bins considered above were subsequently used in combination with an affine and an elastic registration algorithm to derive transformation parameters allowing the combination of all acquired data in a particular position in the respiratory cycle. Images were assessed in terms of signal to noise ratio and contrast. The methodology was finally applied to a minipig and a human study.
Results: Superior contrast was measured in the combined images using the affine respiratory motion model and the diastole cardiac bin. No such dependence on the cardiac gates included in the respiratory bins was seen in the case of the corrected images derived using the elastic respiratory motion model. For the phantom study three amplitude or phase respiratory bins seem to be adequate for both motion models used.
Conclusions: Respiration corrected cardiac images acquired over the diastole phase lead to reduced motion artefacts as well as improved contrast.
- Society of Nuclear Medicine, Inc.