Experimental Results on the Classification of UTE and McFlash Sequences Giovanni Motta Jan 21, 2005.

Experimental Results on the Classification of UTE and

McFlash Sequences

Giovanni Motta

Jan 21, 2005

Unupervised Classification

• Voxels are divided into 16 classes with a K-means algorithm

• A class is assigned to each voxel, similar voxels belong to the same class

• Classification is visualized with maps where different colors represent different classes

• At the present, color assignment is random; some color assignments look “better” (more contrasted) then other. Evaluating the results may be hard because of this

Unupervised Classification

• The classifier is trained on a ROI that is manually selected for each image

• The ROI excludes the background• Results are reported for classification of:

– Original voxel vectors V(i,j)– Mean removed voxels V(i,j)- mean(V(i,j))– Unitary voxels V(i,j)/|V(i,j)|– Mean removed, unitary voxels

(V(i,j)- mean(V(i,j))) / | V(i,j)- mean(V(i,j)) |

Sequences

• UTE

• Fat saturation

• 4 echoes

• 20 sequences 256x256 (4) or 320x320 (16)– TE = 0.08, 3.25, 6.42 and 9.59ms (2)– TE = 0.08, 4.53, 8.98 and 13.5ms (11) – TE = 0.08, 5.81, 11.6 and 17.4ms (4)– TE = 0.08, 6.90, 13.8 and 19.6ms (3)

UTE_0001

Original Mean Removed Unitary Mean + Unitary

UTE_0002


UTE_0003


UTE_0004


UTE_0005


UTE_0006


UTE_0007


UTE_0008


UTE_0009


UTE_0010


UTE_0011


UTE_0012


UTE_0013


UTE_0014


UTE_0015


UTE_0016


UTE_0017


UTE_0018


UTE_0019


UTE_0020


Sequences

• McFlash

• Non fat saturated

• 9 echoes

• Classification on the original voxels and on the voxels after Mark’s SVD denoising

McFlash (Noisy)

Unitary Mean + Unitary

Original Mean Removed

McFlash (SVD Denoised)

Unitary Mean + Unitary

Original Mean Removed

To Do

• Find a criterion to assign a unique colormap so that results can be easily compared

• Compare with classification based on parametric representation (Ma, Mb, etc..)

• Train on specific ROI (fibrosis, HCC, normal liver)

Experimental Results on the Classification of UTE and McFlash Sequences Giovanni Motta Jan 21, 2005.

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