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<p class=MsoNormal><span lang=EN-US>Hi,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>i had a problem concerning the usage of
SpatialObjects (e.g. GroupSpatialObjects, ContourSpatialObjects,
SpatialObjectTreeContainer, PolygonGroupSpatialObjects,
PolygonSpatialObjects...) to mask a specific image for the registration.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I think there are probably other people
doing similar stuff, and there could be interest in discussing a few
implementation decisions concerning SpatialObject child classes and the way the
MeanSquaresImageToImageMetric is processing them.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I use PolygonGroupSpatialObjects and
PolygonSpatialObjects to create my own Volumes of Interest and Contours out of
a set of points.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I use these two SpatialObject types,
because a)i import proprietary structure data, which is not pixel based (Thats
the reason why I don't use ImageMaskSpatialObject for instance).<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> b)the MeanSquaresImageToImageMetric is not
working with any other combination of SpatialObject I tried so far (at least
for the way i nest SpatialObjects).<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I store the Contours in PolygonSpatialObjects
and store all contours of a VOI in PolygonGroupSpatialObjects.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>The Tree SpatialObject for all VOIs is also
a PolygonGroupSpatialObject.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>As mentioned they are actually the only
classes I can use, that’s why I wanted to discuss the implementation of a
few other SpatialObject classes.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>For better understanding, here a part of my
test program in pseudocode :<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>create StructureLoader<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>create RegistrationAlgorithm<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>RegistrationAlgorithm->SetFixedImg()<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>RegistrationAlgorithm->SetMovingImg()<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>RegistrationAlgorithm->SetTargetMask(StrucureLoader->getStructure())
// returns the generated tree node object<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>RegistrationAlgorithm->GetRegistration()
<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>The program delivers correct values(when
trying to determine which image regios are inside/outside the mask) only,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>if I use the PolygonGroupSpatialObjects for
nodes(voi and voi groups) and the PolygonSpatialObjects for leaves(contours).<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>While trying to understand, why my
implementation was not working as planned with other SpacialObject classes
(e.g. GroupSpatialObjects, ContourSpatialObjects), I noticed several
implementation decisions,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>which are responsible for the unexpected
behavior.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I have a few questions concerning the
implementation of
A)MeanSquaresImageToImageMetric::GetValueAndDerivative(...)/GroupSpatialObject::IsInside(...)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> B)PolygonSpatialObject::IsInside(...)/PolygonGroupSpatialObject::IsInside(...)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>and hope that someone is able to explain
them to me.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> A)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> The
MeanSquaresImageToImageMetric::GetValueAndDerivative() calls the IsInside()
method without a parameter for the depth<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> Line 178: if( this->m_FixedImageMask
&& !this->m_FixedImageMask->IsInside( inputPoint ) )<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> which has the effect that for all SpatialObject
classes(at least as far as i know) the default depth=0 is used.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> --> Was this implementation done with
respect to the usage of SpatialObjects?<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> I would assume if someone who is using
SpatialObject would probably like to use the feature of creating tree like
structures by nesting objects,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> but actually there are not many
SpatialObjects which really check for existing childern, and rather use a depth
= 0 as default?<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> e.g. GroupSpatialObjects (i think this
class is a good example, because you would expect a different behavior)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> GroupSpatialObject has no own
implementation of IsInside()<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> So the IsInside() Method checks as follows<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> if( depth > 0 )<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> {<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> do something<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> }<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> else <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> return false<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> --> reasonable you always get false,
when MeanSquaresImageToImageMetric::GetValueAndDerivative(...) checks the
points of the image!<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> Wouldn't it make more sense not to use the
default IsInside implementation, because assuming a default depth=0 for
GroupSpatialObjects seems to make no real sense.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> I can't really imagine, why someone should
use a GroupSpatialObject with a depth of zero (for instance there could be a
check of the childrenList if depth = 0 is passed).<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> This is actually one reason why I use
PolygonGroupSpatialObjects, because it was the only class I could find, which
assumes it has children.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> I didn't check other metrics so far, so i
don't know if they behave the same way.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> B)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> For testing purposes I wanted to use only
one contour of a VOI, for faster processing<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> pseudocode:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> RegistrationAlgorithm->setTargetMask(structureLoader.getContourSpatialObject()->GetFirstVOI()->GetFirstContour());<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> I noticed, that if you use a
PolygonSpecialObject without a PolygonGroupSpatialObjects, you get wrong return
values for IsInside(),<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> because there is no z-dimension check in
the PolygonSpecialObject::IsInside(...) method.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> So if s.o. directly calls the
PolygonSpecialObject::IsInside() method, he gets true for the points even if
they are in an other plane than the polygon.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> this behavour forces you to use a
PolygonGroupSpatialObject even if you would just have 1 PolygonSpecialObject
inside.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US> Can someone explain me, why
PolygonSpecialObject was implemented that way? I think it is quite cofusing for
someone, who works with theses classes the first time, because IsInside just
doesn't behave as you would expect.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US> compare itkPolygonSpatialObject.txx Line
403-485<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>If I take a look at how
MeanSquaresImageToImageMetric is using the IsInside() method, and the way
method is implemented in the different classes, I somehow miss the
"thread" in the way the parts are designed.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>But perhaps I just don't get the concept, I
would appreciate it if someone could elucidate it for me ;). If someone thinks
the way I build my Structures is a unfavorable solution, hints and tips are
always welcome!<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal>Best regards<o:p></o:p></p>
<p class=MsoNormal>Andreas<o:p></o:p></p>
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