[Insight-users] 3D image registration

[Luis Ibanez]

Hi Grace,

The reason why a Versor has only three components,
while a Quaternion has four, is that Quaternions
can describe rotations and scaling.

When you use quaternions for describing only rotations,
you must use unit quaternions.  A versor is simply a
unit quaternion.

So... when people talk about using Quaternions, they
usually mean (or think) of Versors, even though they
don't call them that way.

Versor is the original name the Hamilton used for this
concept when he introduced Quaternions in 1866.

You will find more information about Versors in the ITK
Software Guide


     http://www.itk.org/ItkSoftwareGuide.pdf



   Regards,


      Luis



-------------------
Grace Chen wrote:
> Hi Luis,
> 
> Thank you for your help!
> 
> I don't know why the technicians choosed the low frequency scan rate.  Given
> such a data with thick spacing between slice, I can only do my best to
> correct the movement...
> 
> Since our data is MR scan on brain, we can be sure that it's a 3D rigid
> movement.  I found in the ITK user manual about how to use
> VersorRigid3DTransform.  However, my question is, since there are four parts
> constituting a quaternion, how come the class has only 3 parameters for the
> rotation?
> 
> Thanx a lot!
> 
> Grace
> 
> ----- Original Message ----- 
> From: "Luis Ibanez" <luis.ibanez at kitware.com>
> To: "Grace Chen" <Grace.Chen at swri.ca>
> Cc: <insight-users at itk.org>
> Sent: Thursday, September 08, 2005 6:53 PM
> Subject: Re: [Insight-users] 3D image registration
> 
> 
> 
>>Hi Grace,
>>
>>The registration framework of ITK will manage images with non-isotropic
>>spacing. The registration process is fully done in physical coordinates,
>>so it is immune to the various spacings of your datasets.
>>
>>You may want to read details on this in the Image Registration Chapter
>>of the ITK Software Guide
>>
>>         http://www.itk.org/ItkSoftwareGuide.pdf
>>
>>and the Tutorial on registration
>>
>>http://www.itk.org/CourseWare/Training/RegistrationMethodsOverview.pdf
>>
>>
>>
>>
>>Each one of the datasets may have different spacings along X, Y and Z,
>>and different from the other dataset. The datasets can also have
>>different number of pixels along each dimension.
>>
>>
>>
>>Than being said....
>>
>>Acquiring datasets with large inter-slice spacing is just
>>*BAD-ENGINEERING* ...  very very bad engineering.
>>
>>Doing this is to let Claude Shannon die in vain,
>>(along with his sampling theorem).
>>
>>The practice of acquiring datasets with hight in-plane resolution
>>and large inter-slice spacing is a bad legacy from the tendency of
>>clinicians to still look at the datasets slice by slice and fool
>>themselves with the illusion that the dataset looks great.
>>
>>Each member of the medical image processing community has the
>>moral responsibility of educating her/his fellow clinicians on
>>how bad is to acquire dataset in such poor configurations.
>>The easiest way to provide that education is to show them how
>>bad a dataset look like when viewed in an orthogonal view, where
>>the pixels have anisotropic ratios of 10:1.
>>
>>
>>
>>    Regards,
>>
>>
>>       Luis
>>
>>
>>-----------------
>>Grace Chen wrote:
>>
>>><> Hi all,   I post my question a few days ago and didn't get any
>>>feedback.  So, I post my question again in the next pargraph hoping
>>>someone today will be able to help me with this problelm.  I am a new
>>>ITK user, so my question should be trivial for those who use ITK's
>>>registration tools.  Please help!! :>  Thanx!!   ----- Original Message
>>>----- *From:* Grace Chen <mailto:Grace.Chen at swri.ca> *To:*
>>>insight-users at itk.org <mailto:insight-users at itk.org> *Sent:* Thursday,
>>>September 01, 2005 12:00 PM *Subject:* [Insight-users] 3D image
>>>registration
>>>Hi there,  Good day!   We are using ITK for registering 2D images for
>>>our current project.  It's working very nicely for correcting most of
>>>the misalignment in our data.  However, we noticed out-of-plant movement
>>>in our image data, so we want to extend our project to perform 3D
>>>rigid registration.  The data I have is the MR scan for the brain.  The
>>>dimension of the image is (256, 256, 8), and the spacing is (0.93mm,
>>>0.93mm, 7mm).
>>>So, our problem is: since the space between neighbor slices is so
>>>distant, can the ITK
>>>registration program perform 3D registration properly on this type of
>>>data? ...or do we have to
>>>use some additional VTK/ITK tools to cope with that?   If we can use ITK
>>>to register our data, can you recommand the registration component good
>>>for our data?   Any help is greatly appreciated!! :>   Have a great day!
>>>  Grace
>>>
>>>------------------------------------------------------------------------
>>>
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>>>
>>>
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>>>
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>>
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> 
> 
> 
>