Lesion Segmentation Methodology

Purpose

• Currently in a dilemma as Hagen did a substantial amount of work editing the z-score FLAIR masks in MNI space, but realize that it is more standard to do such work in patient space

• Goal of this presentation is to determine how much of Hagen’s work can be salvaged and how much editing needs to be redone with the new patient space method

• Secondary goal is to determine if zscore > 2 is a good method for selecting DAWM

3 Methods to Choose From

• Z-score in MNI -> threshold (4, 2) -> patient space -> threshold (.95, .5, 0)– The original method, Hagen edited these

• Z-score in MNI -> patient space -> threshold (4, 2)– “z-score in MNI”

• Mean and std. dev. in MNI -> patient space -> z-score -> threshold (4, 2)– “z-score in patient space”

P015 – Low CIS – FLAIR

P015 – Low CIS – Original Method, Lesion Cores, Threshold .95

P015 – Low CIS – Original Method, Lesion Cores, Threshold .5

P015 – Low CIS – Original Method, Lesion Cores, Threshold 0

P015 – Low CIS – z-score in MNI, Lesion Cores

P015 – Low CIS – z-score in patient space, Lesion Cores

P015 – Low CIS – z-score in MNI, Lesion Penumbra

P015 – Low CIS – z-score in patient space, Lesion Penumbra

P009– Low CIS – FLAIR

P009– Low CIS – Original Method, Lesion Cores, Threshold .95

P009– Low CIS – Original Method, Lesion Cores, Threshold .5

P009– Low CIS – Original Method, Lesion Cores, Threshold 0

P009– Low CIS – z-score in MNI, Lesion Cores

P009– Low CIS – z-score in patient space, Lesion Cores

P009– Low CIS – z-score in MNI, Lesion Penumbra

P009– Low CIS – z-score in patient space, Lesion Penumbra

Observations

• z-score in MNI and in patient space give very similar results, I would argue for z-score in MNI as the better choice for simplicity

• The Original Method with threshold 0 is reasonable balance between lesion cores and penumbra, needs a look at by expert eyes

• Threshold z-score > 2 fills in obvious DAWM around lesion cores nicely– Not so great job with areas that did not contain a core

Proposed Options

• Lesion cores– Keep Hagen’s masks and threshold at .5 after

warping to patient space– Alternatively, carry through z-score in MNI method

and apply penumbra selection method to them using Hagen’s masks

• Lesion penumbra (DAWM)– Z-score in MNI method thresholded at 2 then

penumbra selection