[Insight-users] Measuring tumor diameter

[Neuner Markus]

Hi,

I would sggest an approch that is called:  "Bounding Sphere"
and is commonly used in graphics to calculate bounding spheres that are 
independent of object rotations.

Several methods exist to compute a bounding spere and some good examples 
of how to compute and implement this is outlined in the book "Real-Time 
Collision Detection" from Christer Ericson.

One good method is to use the direction of maximum spread from a PCA 
(primary component analysis) of all "contour points".
Then you pick points farhest away along this direction (1st 
eigenvector). This is done by projection (Dot-Product) of the points 
onto the direction vector and you increase the diameter of a shpere 
until all points are inside.

I dont know if PCA is implemented in ITK to compute the 
covariancematrix, eigenvectors and eigenvalues of a point set.


Regards, Markus


Andriy Fedorov wrote:
> On Thu, Dec 11, 2008 at 10:17 AM, Somer, Edward <edward.somer at kcl.ac.uk> wrote:
>   
>> Having segmented the tumour I'd try a 3D-distance transform to find the
>> interior pixel furthest from any edge of the mask. Isn't the maximum
>> diameter then twice the value of the distance transform at this point?
>>
>>     
>
> This will not work, unfortunately. Here's a counterexample.
>
> Imagine I-like shape of some thickness in 2d. Then the maximum
> distance from distance transform will be half the thickness of the
> shape. However, the diameter will be equal to the *length* of this
> shape. So in this case you are getting non-maximum diameter with the
> approach you suggest.
>
>
>   
>> Perhaps I'm missing something,
>>
>> Ed
>>
>> Andriy Fedorov wrote:
>>     
>>> Luis,
>>>
>>> I am actually looking for an automatic tool.
>>>
>>> The approach I am currently considering is this:
>>>
>>> 1) go through the axial slices, find the one with the largest area
>>> 2) extract that slice contour
>>> 3) go through all possible combinations of the contour points, find
>>> the pair of most distant points, and take this as a diameter
>>> 4) follow the line between the points in the previous step, and
>>> subtract the parts of the line that are outside the contour (this is
>>> how the tumor measurements are actually taken). This may change the
>>> measured diameter.
>>> 5) repeat steps 3 and 4 until the maximum is found after taking into
>>> account diameter parts outside the countour
>>>
>>> The problem of course is that this procedure will be quadratic to the
>>> number of contour points, and I am looking for ways to speed this up,
>>> or find an existing implementation, or find a better way to find the
>>> farthest point. I thought about kd-tree to optimize point location,
>>> but I am not sure how to use it for farthest point.
>>>
>>> Any comments are welcome
>>>
>>> Andriy Fedorov
>>>
>>>
>>> On Thu, Dec 11, 2008 at 9:47 AM, Luis Ibanez <luis.ibanez at kitware.com>
>>> wrote:
>>>
>>>       
>>>> Hi Andi,
>>>>
>>>>
>>>> Are you looking for an automatic tool ?
>>>> or for an interactive method ?
>>>>
>>>> In VTK you will find 3D Widgets designed
>>>> for taking measurements in-plane.
>>>>
>>>>
>>>>  Regards,
>>>>
>>>>
>>>>    Luis
>>>>
>>>>
>>>> ------------------------
>>>> Andriy Fedorov wrote:
>>>>
>>>>         
>>>>> Hi,
>>>>>
>>>>> I need to measure the longest diameter of a 3D tumor segmentation. I
>>>>> was wondering, if anybody is aware of any existing tools for this
>>>>> purpose? If not, are there tools to quickly measure the diameter of a
>>>>> 2D projection of the segmentation?
>>>>>
>>>>> I just wanted to have the community opinion before starting to
>>>>> implement something myself.
>>>>>
>>>>> Andriy Fedorov
>>>>> _______________________________________________
>>>>> Insight-users mailing list
>>>>> Insight-users at itk.org
>>>>> http://www.itk.org/mailman/listinfo/insight-users
>>>>>
>>>>>
>>>>>           
>>> _______________________________________________
>>> Insight-users mailing list
>>> Insight-users at itk.org
>>> http://www.itk.org/mailman/listinfo/insight-users
>>>
>>>       
>> --
>> Edward Somer, PhD.
>> Senior PET Methodologist
>> The PET Imaging Centre St Thomas' Hospital
>> London, UK
>> SE1 7EH
>>
>> work tel: +44 (0) 20 7188 1497
>> work fax: +44 (0) 20 7620 0790
>> e-mail: Edward.Somer at kcl.ac.uk / Edward.Somer at googlemail.com
>>
>>
>>
>>     
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