What is the difference between slice thickness and slice increment?

Slice thickness and slice increment are central concepts that surround CT/MRI imaging. Slice thickness refers to the (often axial) resolution of the scan (2 mm in the illustration). Slice Increment refers to the movement of the table/scanner for scanning the next slice (varying from 1 mm to 4 mm in the illustration).

It is acceptable and common to have an overlap in these values. The slice thickness is an important factor in understanding the resolution of your images. If the scan has a slice increment greater than the slice thickness, there is no information about the skipped section, so anatomical information or objects might not show up on the scan.

Click on "Image" > "Organize Images", and you will see listed the slice increment of each slice (0.625 mm in the example shown here). The slice increment is important as Mimics uses this for calibrating the project to ensure all measurements are correctly performed. Slice thickness is displayed in Project Information as copied from the DICOM Headers. Both slice thickness and slice increment play a role in performing a 3D (Gray Value) interpolation in Calculate 3D.