6 thoughts on “What is B value difference between DWI & ADC?”

  1. Hi naeem .

    Just consider this B value 0 is basically a low SNR T2 WI , then we apply different B values , ranging from 50-1000 or even 1400 then obtain multiple image series and sepedate data sets.
    ADC is like a mathematical extrapolated graph represented in imaging.

    Watch my video for more.

    youtu.be/io3aIy6VY2w

  2. lets say this to summarize it.
    T2 WI GRE iMaGe +b-value/factor = DWI

    NOW DWI of various b values are summed up together and mean value obtained to get ADC. not in straightforward method. (Involves complex calculations, which is irrelevant for us radiologist

  3. Please understand this without any confusion.

    Diffusion weighted imaging gives us a measure of how freely the water molecules are able to move in the tissue being examined.
    If there is no pathology the water molecules will show “facilitated diffusion”, if there is a pathology like abscess or infarction or tumor the movement will be reduced called “restricted diffusion”.

    How are DW images obtained?

    Imagine a stack of multiple T2 images arranged one after the other like a pack of cards. Now, these DW images are obtained at various “b-values.” A b-value is nothing but the measure of a gradient that is applied across the stack of images we talked about.

    As the gradient is increased, that is as the b value is increased, the T2 component of the image is masked and the diffusion component of the image is increased.

    What is T2 shine through?
    As I said, imagine the stack of T2 images. At lower b values we can see a bright signal on DW images but that signal might not be due to restricted diffusion of water rather the inherent T2 brightness of the tissue.
    This is the reason a confident finding of diffusion restriction can only be made at high b value images.

    What is ADC?
    An ADC is nothing but a numerical measurement of the diffusion restriction present in the tissue. It is a derivative of the DW image and is NOT directly dependent on b values.

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