[vtkusers] Hounsfield Units : strange result (Volume rendering)

[Kevin Osborn]

Don't forget air surrounds the patient. What your image shows is the 
air/skin interface, not the skin itself. As the lung is mostly air, your 
Hounsfield range between -600 and -400 not only gives lung but also 
includes air around the patient.


wassim_belhadj at topnet.tn wrote:
> Hi,
>
> I'am using VTK/VTKEdge and QT4 for volume rendering.
>
> I 'am using a CT Datasets of a young person ( 35  years old)
>
> I'm trying to define values of pixel that define lungs.
>
> I assigned opacity to each pixel by checking its intensity value  with
> Hounsfield Units values. 
>
> Bone         +400 -----------> +1000
>
> Soft tissue  +40 -----------> +80
>
> Fat          -80 -----------> -100
>
> Lung         -400 -----------> -600
>
>
> I got a strange result !!  The volume obtained contains the lungs and skin 
>
>  
> According Hounsfield Units, the pixel values that form the skin and lungs
> are not in the same interval.
>
> I varied the opacity values to eliminate the skin that surrounds the lungs
> but I have not succeeded.
>
> Attached a screenshot that illustrates the problem.
>
> Can someone help me ?
>
> Best Regards,
> BEHADJ wassim