[Insight-users] Confused about pixel Spacing

[Kishore Mosaliganti]

You can use it, just be consistent. It defines the scale space. Your
x-y-z spacings are all isotropic probably. Else you will have to
preserve the ratios.

In the future, when you (or someone else) looks at your code, you/they
will most likely not remember anything about the pixel spacing and
get/use erroneous results.

For example., they make take the image with 1 unit spacing and apply a
0.00283 units Gaussian kernel smoothing which will then have no
effect. The 2.83mm pixel spacing is lost forever or stored somewhere
else.

If you don't stick to the convention, then your code is usable only to you.

Kishore

On Thu, Nov 12, 2009 at 3:31 AM, Auron Ford Huton <auron at hotmail.es> wrote:
> Thank you for your answers!!
>
> Now I have another doubt... If I can use 0.00283 an 2.83 indifferently, why
> can´t I used just a pixel spacing of 1??
>
> Not if I can explain, is really so important to used a correct pixel spacing
> for registration or it´s ok if I use an value of 1 for the spacing (always
> being consisten all over the code)?
>
> Thank you all!
>
> Auron.
>
>> Date: Wed, 11 Nov 2009 15:21:59 -0500
>> Subject: Re: [Insight-users] Confused about pixel Spacing
>> From: kishoreraom at gmail.com
>> To: auron at hotmail.es; cquammen at cs.unc.edu
>> CC: insight-users at itk.org
>>
>> Once you choose a certain spacing, remember to consistently use that
>> in all the subsequent processing filter settings such as sigma of
>> Gaussian etc. In most filters, you will have the option
>> SetUseImageSpacingOn() or Off() that you should also use. The output
>> at any intermediate stage will also have the same units.
>>
>> It is better to use the 2.83 micrometer value since the other value
>> seems very cumbersome to handle.
>>
>> Kishore
>>
>> On Wed, Nov 11, 2009 at 1:47 PM, Cory Quammen <cquammen at cs.unc.edu> wrote:
>> > Auron,
>> >
>> > The units you choose for pixel spacing (meters or micrometers) do not
>> > matter. It only matters that you are consistent in what unit you use
>> > to set the spacing for both the fixed and moving images.
>> >
>> > Hope that helps,
>> > Cory
>> >
>> > On Wed, Nov 11, 2009 at 12:58 PM, Auron Ford Huton <auron at hotmail.es>
>> > wrote:
>> >> Hello ITK!!
>> >>
>> >> I am working in microscopy image registration and I doubt how to
>> >> express my
>> >> pixel spacing (I think all my problems came from that...). I know that
>> >> my
>> >> pixel spacing is about 2.83 micrometres (0.00283mm).
>> >> I am using .raw image so I used a .mhd to acces them... What of the
>> >> following lines I should use to set my spacing?
>> >>
>> >> ElementSpacing = 0.00283 0.00283
>> >>
>> >> or
>> >>
>> >> ElementSpacing = 2.83 2.83
>> >>
>> >>
>> >> Thank you in advance.
>> >>
>> >> Auron.
>> >>
>> >> ________________________________
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>> >>
>> >
>> >
>> >
>> > --
>> > Cory Quammen
>> > Center for Computer Integrated Systems for Microscopy and Manipulation
>> > (CISMM)
>> > Department of Computer Science
>> > University of North Carolina at Chapel Hill
>> > http://www.cs.unc.edu/~cquammen
>> > _____________________________________
>> > Powered by www.kitware.com
>> >
>> > Visit other Kitware open-source projects at
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>> >
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>
> ________________________________
> ¡Nuevo Canal Mujer! Moda, belleza, sexo, dietas, embarazo. más fácil y a tu
> alcance. Si quieres estar a la última, no puedes perdértelo.
> _____________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Kitware offers ITK Training Courses, for more information visit:
> http://www.kitware.com/products/protraining.html
>
> Please keep messages on-topic and check the ITK FAQ at:
> http://www.itk.org/Wiki/ITK_FAQ
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>