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| ID | Project | Category | View Status | Date Submitted | Last Update | ||||||||
| 0005573 | ITK | public | 2007-08-24 22:51 | 2010-10-26 05:57 | |||||||||
| Reporter | Steve Robbins | ||||||||||||
| Assigned To | Mathieu Malaterre | ||||||||||||
| Priority | normal | Severity | major | Reproducibility | always | ||||||||
| Status | assigned | Resolution | open | ||||||||||
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| Target Version | Fixed in Version | ||||||||||||
| Summary | 0005573: Image::DirectionType should be Nx3 rather than NxN | ||||||||||||
| Description | Currently, ImageBase for an image of dimension N will define the Origin, Spacing and direction cosines (DirectionType) in terms on N-vectors. This is incorrect. DICOM scanners routinely produce 2D images set in a 3D world space. 4D image series (3D + time) also exist within a 3D physical space. In short: the dimension of the physical space is independent of the image dimension. Is there some way to introduce the physical space dimension as a ImageBase template parameter? The issue was raised and acknowledged on insight-developers recently, c.f. http://www.itk.org/mailman/private/insight-developers/2007-July/009201.html [^] | ||||||||||||
| Tags | No tags attached. | ||||||||||||
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(0009012) Luis Ibanez (manager) 2007-09-17 08:48 |
This is arguable... It makes sense for a 2D DICOM slice to have a 3x3 direction when it is considered to be a 1-slice 3D image embedded in 3D space. An application that reads such an image should actually instantiate a type itk::Image< PixelType, 3> ImageType not a type itk::Image< PixelType, 2> ImageType The 4D case, is a bit more challenging to interpret, although in this case we will have at hand a 4x4 matrix for storing a 3x3 one, and therefore the only issue is the waste of the 6 other terms that always will be set to zero. |
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(0009044) Steve Robbins (developer) 2007-09-18 01:55 |
I guess this depends on how you interpret the VImageDimension template parameter in itk::Image. The documentation states Images are templated over a pixel type (modeling the dependent variables), and a dimension (number of independent variables). -- http://www.itk.org/Doxygen32/html/classitk_1_1Image.html [^] To me, the "number of independent variables" for a planar image is naturally 2. Though I haven't canvassed other ITK users, I suspect that is the common interpretation. In support of this, note that (a) Teem's nrrd separates "dimension" from "space dimension" [1] and (b) ITK's own GDCM ImageIO class goes out of its way to provide the 3-vector origin and direction cosines for 2D images [2]. [1] http://teem.sourceforge.net/nrrd/format.html [^] [2] http://www.itk.org/mailman/private/insight-developers/2007-July/009203.html [^] Time series data is also a problem. If I have a single slice imaged over time, I would naturally consider that a 3D image (2 spatial + 1 time). The itk::Image would provide me with a 3D Origin and cosines, but the third component of these vectors has nothing to do with the third component of the image dimension (time). If I have a volumetric time series -- i.e. 4D data, then I end up with a 4D Origin and cosines. This is a complete nuisance to do any world-space math with; e.g. distance or angle measurements. |
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(0010259) Luis Ibanez (manager) 2008-01-23 16:05 |
More discussion is required to find a new configuration that serves all the uses of ITK. In the meantime, we probably should address the specific concerns of how to use directions in 3D+t image. This could probably be done better by creating helper classes that are aware of the 4D: 3D+t nature of the problem. SMR: Could you list the use-cases that you need to address in you 3D+t problem ? Thanks Luis |
| Notes |
| Issue History | |||
| Date Modified | Username | Field | Change |
| 2007-08-24 22:51 | Steve Robbins | New Issue | |
| 2007-09-17 08:48 | Luis Ibanez | Note Added: 0009012 | |
| 2007-09-18 01:55 | Steve Robbins | Note Added: 0009044 | |
| 2008-01-23 16:03 | Luis Ibanez | Status | new => assigned |
| 2008-01-23 16:03 | Luis Ibanez | Assigned To | => Luis Ibanez |
| 2008-01-23 16:05 | Luis Ibanez | Note Added: 0010259 | |
| 2008-01-23 16:05 | Luis Ibanez | Status | assigned => feedback |
| 2010-10-26 05:57 | Mathieu Malaterre | Status | feedback => assigned |
| 2010-10-26 05:57 | Mathieu Malaterre | Assigned To | Luis Ibanez => Mathieu Malaterre |
| Issue History |
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