[Insight-users] Problem with DRR generation

[Jian Wu]

Hi Luis,

Thanks for your work. But the problem is still there. Please try to use the 
following parameters for the test.

DigitallyReconstructedRadiograph1 -res 2 2 -o CubeDRR.img

The output image was not centered. Moreover, it appears the ray that passes 
through the origin of the 3D image is not normal to the 2D image plane. 
Please check it out.

By the way, I have a suggestion. In medical application, the projection 
geometry is usually specified by a source-to-image distance (sid) and a 
source-to-object ditance (sod), i.e., the distance from the source to the 
origin of the 3D volume. It would be more practical if those two parameters 
were used in the code instead of using a focal length and positioning the 3D 
volume half way between the source and the screen.

Jian Wu

>From: Luis Ibanez <luis.ibanez at kitware.com>
>To: Jian Wu <eewujian at hotmail.com>
>CC: insight-users at itk.org, samant at ufl.edu, mmhuang at ufl.edu,        
>xiajunyi at hotmail.com, john.hipwell at kcl.ac.uk, thomas at hartkens.de
>Subject: Re: [Insight-users] Problem with DRR generation
>Date: Thu, 29 Dec 2005 08:27:41 -0500
>
>
>Hi Jian,
>
>Looking at the Code of the DigitallyReconstructedRadiograph1.cxx
>it seems that it is missing to take the image origin into account.
>
>
>If your image has an origin different than zero, the computation
>of the image center will be incorrect.
>
>
>We just committed a fix for this issue to the CVS repository.
>You may want to update your CVS checkout (if you have one)
>or you can apply the same corrections to your local code.
>
>
>The modifications can be found at:
>http://www.itk.org/cgi-bin/viewcvs.cgi/Examples/Filtering/DigitallyReconstructedRadiograph1.cxx?root=Insight&sortby=date&r2=1.15&r1=1.14
>
>
>
>   Please let us know if you find any problems,
>
>
>
>      Thanks
>
>
>         Luis
>
>
>
>---------------
>Jian Wu wrote:
>>Dear ITK users:
>>
>>I'm wondering if anyone have generated correction DRRs using the example 
>>programs GenerateProjection.cxx or DigitallyReconstructedRadiograph1.cxx.
>>
>>I ran both codes using the parameters and the image given in the 
>>README.txt file. But the generated DRRs appear to have a different 
>>projection and image center than I expected.
>>I also tried to simply the test data in 
>>DigitallyReconstructedRadiograph1.cxx. Instead of using the orignal cubic 
>>structure, I constructed a 61x61x61 3D image with a single point at the 
>>center of the image. The resulting DRR has a point centered at pixel index 
>>(81, 81). The DRR has the size of 501x501, and the point is supposed to be 
>>at the center of the image. I can't figure out how the projection works. I 
>>really wish the projection geometry were better documented.
>>
>>When real CT data sets were used, the objects in the output DRRs appear to 
>>have been shifted toward the left-bottom corner of the images. I searched 
>>the emails that have been posted before. It appears someone has pointed 
>>out the problem before. However, I did not find any answers to the 
>>question. By the way, the IntensityBased2D3DRegistration.cxx example code 
>>does not work. I have posted the problem a couple of days ago.
>>
>>Someone help me out please!
>>
>>Jian Wu
>>
>>
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>>
>>
>