Z-axis Geometry

The Z-axis geometry is calculated from the three 0.5mm diameter beads spaced at 10mm increments, covering a total of 20mm in the z-direction.

Figure 7.1: Diagram depicting the z-axis distance between the 0.5mm diameter z-axis geometry beads.

The signal intensity for each bead is calculated for each slice in the image set. These signal intensity profiles are plotted against their relative position [mm], along with a sinc interpolation of the intensity. This intensity profile is used to interpolate the precise z-position of each bead. This z-position is then used to assess the measured distance between beads with a comparison to the expected position.

The slice where the maximum intensity occurs is also recorded. The maximum pixel intensities for each of the three peaks is expected to be 10 slices or 10 mm apart.

Table 7.1: Table provided in the Smári report in the Z-axis geometry section. Measures the distance (z) between the z-axis geometry beads and compares it to the expected distance (z).

The slice sensitivity profile, in this case, shows the drop off in signal as the slices get further from the slices with the beads.

Figure 7.2: Above is a Slice Sensitivity Profile from the Smári Analysis Tomophan® QA. Plotted from left to right on the graph, are the pixel intensity measurements from each slice and the sinc interpolation of the intensities of the upper bead (purple triangles and red line), the middle bead (green squares and orange line), and then the lower bead (blue circles and black line).