[Insight-users] Measuring tumor diameter

[Andriy Fedorov]

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
>>>>
>>>>
>>
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>>
>
>
> --
> 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
>
>
>