Task-Based Help - Brain Volumes
In this second example, we will measure the total volume of
brain tissue - the sort of measurement that can be used to assess
brain atrophy rates - and the brain parenchymal fraction (BPF) a
normalised measure of the degree of brain atrophy. For this measurement we will use a
T1-weighted MR image, where the CSF appears hypointense.
- First you need to load you image into Jim. Either
load the image directly or use the
image converter to load an image.
- Next, bring up the Brain
Finder tool. This will be used first to isolate the brain and CSF from any
surrounding cranial tissue on each slice of
the image.
- If automatic outlining fails or needs correction,
you will need to edit the
brain outline or draw the
outline manually. Try to include as much brain and CSF as
possible within the outline, but no other tissue.
- Now calculate the volumes of the brain parenchyma and CSF, and
calculate the BPF by following the instructions in Calculating the BPF.
Note: If the image was acquired with an inter-slice
gap, the computed volumes should be corrected by multiplying the
volume by:
(slice-thickness + inter-slice-gap) / slice-thickness.
- You are now ready to progress to the next scan to be
measured. Proceed from step 1.