Diagram illustrating the two aspects of temporal resolution. is determined by the rotation time and reconstruction algorithm. is determined by the heart rate and the number of phases that we chose to reconstruct (5 in this example).
Diagram illustrating the process of ECG gating. The light gray band indicates the covered positions of the detector during the scan. The dark gray patches represent parts of the phase in each heart beat. The horizontal lines that connect the patches indicate the measured position in subsequent parts of the same phase. They show the overlap [as in (a)] or volume gap [as in (b)] between the patches that belong to the same phase. The dotted vertical lines indicate the time at which the gantry is at 0°.
Schematic drawing of the phantom used for detecting motion. The phantom consists of a PMMA cylinder with stent wire fragments embedded at intervals.
Schematic drawing of the setup. The motion unit (M) drives the phantom (Fig. 3) inside the CTDI phantom’s center hole, which is depicted in front of the gantry (G). The left and right hand sides show the setup for measuring in the and directions, respectively.
Illustration of the correlation between subsequent phases against the number of phases (a) and against the time between phases (b). The dashed line in (b) is a linear fit through the seven data points left of the mark.
Illustration of the moving position of the points for different amplitudes.
Illustration of the error versus amplitude. The solid line represents the mean absolute error. The dotted lines are the 25 and 75 percentile of the sorted absolute error of the data points in each experiment. The dotted 45° line indicates where the error and amplitude are equal.
Illustration of the error versus frequency. The solid line represents the mean absolute error. The dotted lines are the 25 and 75 percentile of the sorted absolute error.
Example of the detected motion (solid) of a point at and the known profile (dotted). The horizontal boxes indicate the temporal width of .
Illustration of the shape (left) and the Fourier response (right) of a pressure profile in the aortic artery, as reported in literature (Ref. 26).
Illustration of the noise bands in the CT images caused by the volume gaps due to a too low heart rate during scanning. At , the (horizontal) noise bands are clearly visible (indicated by the arrows). It can be seen how it hides the second bar from the top. At , the noise bands are very thin. At higher heart rates, no noise bands can be detected.
The motion patterns used in the experiments. A0–A6 vary in amplitude, while B0–B6 vary in frequency.
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