Abstract
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Objectives This study introduces a new motion correction technique, which combines cardiac ECG gating and bioimpedance-based respiratory gating in cardiac PET.
Methods Cardiac PET/CT studies were conducted with 12 patients in one bed position (10min, listmode). ECG and transthoracic bioimpedance were measured simultaneously using standard ECG locations (II limb lead). The bioimpedance measurement was used to monitor electrical conductivity variation in thorax due to changes in respiratory depth and thorax shape and allowed the delineation of direct respiratory motion [1-3]. Attenuation corrected static (ST), end-expiratory (RE), end-diastolic (CA) and dual-gated (end-expiratory and -diastolic, DUAL) images were reconstructed (3D-OSEM, 3i21s, no filter). To evaluate the effect of gating, images were analyzed for ventricle volume and lateral wall thickness (FWHM) basal to papillary muscles.
Results Respiratory and cardiac gating were successful in all patients. In ventricle volume analysis (7 patients) the median difference between ST vs. RE, ST vs. CA, ST vs. DUAL and CA vs. DUAL images were 3ml, 24ml, 30ml and 1ml, respectively. Respiratory gating resulted in small wall thickness reduction (median 0.5mm, NS, Wilcoxon) compared to ST images. Dual-gating reduced wall thickness significantly (5.2mm, p=0.002). Wall thickness reduction from CA to DUAL was small (0.4mm, NS), but reached 4.6mm in one patient.
Conclusions This study shows the feasibility of a new dual-gating method for cardiac PET. The technique is easily adoptable and enables simultaneous cardiac and respiratory gating using only 4 electrodes. In addition, the volume analysis of this study implies that the advantage of dual-gating over cardiac gating may be limited in measurements of global cardiac parameters. Based on relevant thinning of wall thickness in single patients in this study, dual-gating may offer increased signals in imaging of certain molecular targets, such as in myocardial inflammations.