Slide 9 of 13
Notes:
- Z-axis resolution can be measured using the ramp or delta impulse methods:
- The Ramp method uses the partial volume effect by scanning an oblique object and determining its extension in the image plane
- Metal sheets or thin wires inclined at an angle towards the scan plane are used.
- This method works perfectly for axial scanning, but it cannot be used for spiral scanning because of Z-axis interpolation artefacts.
- The Delta impulse method Uses either disks of thin foil or beads.
- We used a Tungsten disk to give the required contrast for larger slices
- It was 0.05 mm thick, that is 10% of the smallest possible slice width of 0.5mm
- And to minimise the misalignment effects we used a very small disk about 6 mm in diameter