[Insight-users] MRI geometric distorsion

[Vincent Magnotta]

Teo,

You will need to model the geometric distortion as a transform in ITK.  
This distortion is due to the non-linearity of the gradient system. On 
commercial systems this often modeled and corrected (at least in 2D). If 
you can parametrize or determine the deformation field over the entire 
FOV of your scanner, you could use the position information of the image 
to apply a this deformation to the acquired data. This is assuming that 
the you are not running an EPI sequence where distortions are also due 
susceptibility artifacts. One straight foward and simple (probably not 
optimal) way to model this is to place a grid with a known spacing into 
the scanner. You could then use a thin plate spline transform to correct 
for the distortion.

Anders Dale was working on a tool for geometric correction as part of 
the MBIRN project. I do not know where this project stands.

Vince


Popa Teo wrote:

> Hi,
>  
> Did anybody encounter geometric distorsion in MRI images,especially 
> high-tesla(7) fields.I found that the geometric distorsion is quite 
> obvious when I tried to measure the distance of 3 colinear fiducials 
> with known distance on a in-plane slice.
>  
> Does itk have methods for correcting this distorsion (especialy on 7T 
> magnets for example ) or this should be done by manufacturer of MRI 
> device?
>  
> Teo
>  
> p.s.I know itk has some methods for correcting some characteristics of 
> MRI images(like  MRI bias field correction 
> itk::MIBiasFieldCorrectionFilter).
>
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-- 
Assistant Professor
Department of Radiology
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