Generalization of three-dimensional golden-angle radial acquisition to reduce eddy current artifacts in bSSFP CMR imaging

Figures

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  Fig. 1. Graphical representation of the different trajectories. The golden and tiny trajectories all are perceptually uniform compared to the random trajectory. All trajectories were calculated with the same number of sample points, N = 28,657

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  Fig. 2. Mean angle between successive spokes (dashed line). The solid line represents the angular step with a superior-inferior spoke interspersed every 25th TR

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  Fig. 3. a Schematic illustration of the Clustered-Random-Regular (CRR) metric, together with the conventional golden-means distribution. The top left panel describes a clustered appearance, with CRR < 1. The top right appearance describes a random distribution with CRR = 1. The bottom left panel describes the golden-means distribution with CRR = 1.58 The bottom right panel describes a perfectly regular pattern, with CRR = 2. A quasi-random distribution is expected to fall in the range between 1 and 2. b CRR-values for a selection of tiny orders up to 55, the presented value is the average CRR for the range from 233 to 121,393 spokes

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  Fig. 4. a Representative Voronoi diagrams used to assess the k-space uniformity after binning for the conventional double golden-angle and the proposed Tiny-13 profile ordering. Red points represent the origin or end of a readout spoke. Blue lines represent the boundaries of the Voronoi cells. b Bar plots describing the outcome of the binning simulations. The standard deviation of Voronoi cell areas was calculated for all combinations of respiratory and cardiac phases. Numbers are represented as mean ± SD. The blue bars represent the conventional double golden-angle profile ordering, whereas the red bars represent Tiny-13

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  Fig. 5. Phantom experiments demonstrate the improved image quality from the tiny golden profile orderings. a Normalized average absolute deviation (NAAD) was used to measure the image uniformity in a spherical phantom, which showed increasing uniformity with increasing tiny order. b Corresponding images of a bottle phantom

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  Fig. 6. Phantom experiments indicating reduced sensitivity to off-resonance effects. a Normalized average absolute deviation (NAAD) is measured in a spherical volume of interest in a spherical phantom scanned with both the conventional three-dimensional golden-angle profile ordering, as well as the novel tiny golden-angle profile ordering Tiny-13. b Corresponding images are displayed, corroborating the numerical findings

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  Fig. 7. In vivo images show improved image quality with the reduced angular step, although the difference in eddy current-induced artifacts are not as pronounced as in the phantom experiments. With the conventional double golden-angle profile ordering there is an apparent signal loss in the right atrium and the epicardial fat (indicated by white arrows) which is not present with Tiny-13. Both images were acquired during free breathing and reconstructed from 126,478 spokes. The images represent the end-expiratory respiratory phase and the end-diastolic cardiac phase