[Insight-users] Re: Using RequestedRegion

[Luis Ibanez]

Hi Rakesh,


Thanks for letting us know that you found the reason for the slowdown.


It make sense konw.


Maybe we should add a methods to the Mutual Information metric to
set the number of samples not as a number but as a percentage of
the pixels in the FixedImageRegion.  This will actually be more
consistent with the way we reason while configuring the registration
framework.


That is,
it makes more sense to say :


               "use 10% of the pixels"

than to say

                "use 143,250 pixels".


If you want,
it will be nice to add this as a "Feature Request" to the phpBugTracker.



    Thanks


       Luis



---------------------------------------
Mullick, Rakesh (GE, Research) wrote:
> Hi Luis,
> 
> I figured out what was causing the slow-down - The number of samples was
> not changing and was the same as the original and I was ending up
> multiple (over) sampling the same ROI. I do observe a speed up.
> 
> Thasnks.
> 
> regards,
> rakesh
> ______________________________________________________________________
> Rakesh Mullick, Ph.D., Senior Scientist 	EMail:
> Rakesh.Mullick at ge.com
> 
> 
> -----Original Message-----
> From: Luis Ibanez [mailto:luis.ibanez at kitware.com] 
> Sent: Monday, October 09, 2006 2:27 PM
> To: Mullick, Rakesh (GE, Research)
> Cc: Insight Users
> Subject: Re: Using RequestedRegion
> 
> 
> Hi Rakesh,
> 
> This sounds strange.
> 
> However, notice that you must differentiate between the time
> that it takes to compute *one* value of the image metric and
> the time that it takes to complete the *full* registration.
> 
> Setting the FixedImageRegion should *reduce* the time that
> it takes to compute *one* iteration of the optimizer, but
> depending on your image, it may *increase* the total number
> of optimizer iterations needed to achieve convergence.
> 
> 
> Please post to the list the number of iterations that it took
> you to complete the registration in both cases. I would guess
> that it took you a lot more iterations in the case where the
> FixedImageRegion was set.
> 
> 
> If that is the case, what we could conclude is that the region
> that you selected as FixedImageRegion does not contain enough
> shape specific information as to drive the optimizer, and that
> you probably should include other nearby regions in order to
> give better definition to the cost function.
> 
> 
> For example, if you where registering the lungs, and you select
> a FixedImageRegion that is fully inside the parenchyma, you
> are probably in need of including a small section of the ribs,
> which will provide a clear basin in the topography of the cost
> function.
> 
> 
> Please take a look again to the number of iterations used in both
> cases and let us know what you find. It will also help us to know
> about the Metric that you are using, the Optimizer, and the actual
> size of the FixedImageRegion and the BufferedRegion.
> 
> 
> 
>     Thanks
> 
> 
> 
>        Luis
> 
> 
> 
> ---------------------------------------
> Mullick, Rakesh (GE, Research) wrote:
> 
>>Hi Luis,
>>
>> 
>>
>>I have been experimenting with the use of SetFixedImageRegion for 
>>Registration and observing that when I set a region the registration 
>>takes longer than when I use the BufferedRegion. This is in Release 
>>mode. Will the overhead be so much as to slow down the registration. I
> 
> 
>>am using about 1/10 of the overall volume to drive registration and 
>>observing a 50% increase in clock time to register the same data.
>>
>> 
>>
>>Any thoughts or past threads are welcome.
>>
>>Many thanks.
>>
>> 
>>
>>regards,
>>rakesh
>>______________________________________________________________________
>>*Rakesh Mullick*, Ph.D., Senior Scientist    *EMail*: 
>>Rakesh.Mullick at ge.com <mailto:Rakesh.Mullick at ge.com>
>>
>> 
>>
> 
> 
> 
> 
>