Image normalization and standardization

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rgh
Posts: 2
Joined: Thu 3. May 2012, 21:02

Image normalization and standardization

Post by rgh » Thu 3. May 2012, 21:07

Hi, I have a problem concerning MRI image normalization and scaling data between 0 and 1.
I have three tissue classes with different intensity range on a set of images (intensity range for each tissue is varying from image to image): for one image for instance I have: GM (100-150), L(0-150), WM(150-300). Now I want to normalize L to GM and WM, such that I can say how much brighter or darker L is relative to GM and WM. I was wondering how can I do it? and if I want to show the contrast of L, relative to GM and WM to be between 0 and 1, what will be the equation?
Thanks for your help in advance

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Admin
Site Admin
Posts: 438
Joined: Sun 16. Nov 2008, 18:21

Re: Image normalization and standardization

Post by Admin » Thu 3. May 2012, 21:59

Hi,

I'm not quite sure if I fully understand the question: Do you know the intensity ranges for each picture and now want to tell how much darker or brighter L is?
In this case I suppose something like this is an approach:

ratio(l/GM) = (l - LL) * (LH - LL) / (GMH - GML)
ratio(l/WM) = (l - LL) * (LH - LL) / (WMH - WML)

where
l = Intensity of L in the region of interest
LH = High value of L range over whole image
LL = Low Value of L range over whole image
GMH = High value of GM range over whole image
GML = Low value of GM range over whole image
WMH = High value of GM range over whole image
WML = Low value of GM range over whole image

Just a guess, I'm not quite sure if I got your question correctly...
Thomas Jetter

rgh
Posts: 2
Joined: Thu 3. May 2012, 21:02

Re: Image normalization and standardization

Post by rgh » Thu 3. May 2012, 22:48

My goal is to compare intensity of ROI "L" on a series of images with each other, but each image has a different intensity range.
So I need to normalize intensity of each image first to something on that image, that at the end I be able to show the contrast: so here I have WM, and GM ROIs.

Now to show how much intensity of L brighter or darker is than WM and GM (on the same graph) for each image. So calculating each ratio separately does not help me.

I was thinking of making WM and GM 0 and 1 respectively, so I can show the status of L between this two classes. And I was thinking two point normalization may help me and an equation like this might be helpful,
New L = (Median intensity of "L" ROI - Median intensity of GM ROI) * (1/ (Median intensity of WM ROI -Median intensity of GM ROI))

But my scale didn't become 0 and 1, bust something between -1 and 1 almost.
I don't know which part I did wrong

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