[Insight-users] Measuring tumor diameter

[Celina Imielinska]

  One has to think about doctors who would be willing to use any measure of 
diameter related to a 3D shape of a tumor. Doctors are trained to assess 
size of a tumor looking at 2D slices, cross-sections. They don't trust 
description of 3D tumor shapes and progression/comparison of tumor shapes 
in 3D.  I suggest that you talk to many doctors and find out first what 
they really want - not one doctor who would say incidentally that "this is 
an interesting problem".

   if you want to provide medicine with a potentially useful tool, ask 
first, not necessary impose something that might be good, is logical, 
attractive to work on - but it will never be used in practice.

   I always suggest to read this book, by Atul Gawande "Complications: A 
Surgeon's Notes on an Inperfect Science". It is definitely worth reading.

    Celina

On Sun, 21 Dec 2008, Andriy Fedorov wrote:

> On Sun, Dec 21, 2008 at 11:20 AM, Steve M. Robbins <steve at sumost.ca> wrote:
>>> 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
>>
>> This makes it seem like you have reduced the problem to 2D only.  Is
>> that desirable, or is that done due to convention (e.g. radiologists
>> traditionally look at stacks of 2D slices)?
>>
>
> Based on my discussion with a neurosurgeon, they usually look at 2D
> slices in AP/LR/IS directions, but also they may also look at oblique
> slices.
>
> To understand maximum diameter, as I understand it, imagine the
> contour of the tumor segmented in a 2d slice. Then take a set of
> segments connecting all possible combinations of the contour points.
> For each segment, subtract the subsegment which is outside tumor
> contour (this will happen only for concave shapes). The updated this
> way length of the longest segment will be the maximum diameter.
>
> I assume, one can take all combinations of surface points in 3d,
> instead of looking at a slice with the largest area, but this will be
> very time-consuming to walk along the segments connecting all possible
> pairs of points. I simplify the problem to develop an initial
> solution.
>
>>> 3) go through all possible combinations of the contour points, find
>>> the pair of most distant points, and take this as a diameter
>>
>> Here you are measuring using the normal Euclidean distance?  For
>> example, an "L" shape would have the two most distant points be the
>> end of the two legs and the diameter would join them to form a
>> right-angle triangle?
>>
>
> An "L" shape will have the maximum diameter equal to the length of the
> longer leg. With the diameter you suggest most of it will belong to
> the outside of the shape.
>
>>> 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.
>>
>> I don't understand "subtract the parts of the line outside the contour".
>> In my "L" shape example, almost the entire line is outside; does that
>> mean you would say its diameter is zero?
>>
>
> The diameter defined this way will indeed be almost 0. This will not
> be the maximum diameter though.
>
>>> 5) repeat steps 3 and 4 until the maximum is found after taking into
>>> account diameter parts outside the countour
>>
>> Again, I'm not sure what this means.
>>
>> Naively, I might expect that you want to measure a longest distance
>> through the shape.  In the "L" example, this would be the sum of the
>> two legs.
>
> The diameter by definition should be measured along a line, you cannot
> sum up two legs...
>
>> I googled a bit but did not find any precise explanation of how to
>> measure a "tumour diameter".  Can you explain a bit?
>>
>
> I haven't found a precise definition either. Based on my
> understanding, the measure is very subjective, and it is basically
> what I described. Of course, it is not easy to visually identify the
> largest diameter.
>
> I hope I was able to clarify the problem for you a bit. If you find a
> better definition, please post...
>
> Thanks
>
> Andriy Fedorov
>
>
>
>> Thanks,
>> -Steve
>>
>>
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