[vtkusers] Hounsfield Units of Human body part

[Chasan KIOUTSOUKMOUSTAFA]

HUofAir = (double)(reader->GetPixelRepresentation() * reader->GetRescaleSlope()) + (double) reader->GetRescaleOffset();
// HuofAir represents -1000 HU
HUofBone = HUofAir + 2250.0;  // 1250 HU for Bone
HUofMuscle = HUofAir + 1050.0; // 50 HU for Muscle
HUofFat = HUofAir + 880; // -120 HU for Fat

so, this code must calculate the exact HU value.. Am i right ?
I've four different types of DICOM datasets, two of them is nearly optimal, However other ones optimal bone value is about 200 HU..
is HU values is so dependent to patient ? what can be ?

Chasan KIOUTSOUKMOUSTAFA

--- On Thu, 8/26/10, Scott Johnson <Scott.Johnson at neuwave.com> wrote:

From: Scott Johnson <Scott.Johnson at neuwave.com>
Subject: RE: [vtkusers] Hounsfield Units of Human body part
To: "Chasan KIOUTSOUKMOUSTAFA" <chasank at yahoo.com>, "vtk mailList" <vtkusers at vtk.org>
Date: Thursday, August 26, 2010, 6:06 PM




 
 






Hello Chasan, 

   

The VTK DICOM readers already take the Rescale Slope and
Intercept values into account.  The voxel values from DICOMReader are already
in HU so the offset should not be applied. 

   

The definition of Rescale Slope and Rescale Intercept can be
found in the DICOM Standard Part 3: 

·        
Rescale Intercept             (0028,1052) 

The
value b in relationship between stored values (SV) and the output units.  Output
units = m*SV+b 

·        
Rescale Slope                    (0028,1053) 

m in
the equation specified in Rescale Intercept (0028,1052). 

   

                                --
Scott 

   



From: vtkusers-bounces at vtk.org
[mailto:vtkusers-bounces at vtk.org] On Behalf Of Chasan KIOUTSOUKMOUSTAFA

Sent: Thursday, August 26, 2010 8:17 AM

To: vtk mailList

Subject: [vtkusers] Hounsfield Units of Human body part 



   


 
  
  
  
   
    
    Hi all

     I'm trying to get iso surfaces of a human-body parts such as ( bone,
    liver, muscle, skin) from DICOM datasets. For extraction of iso surfaces,
    I'm using the MarchingCubes algorithm, and it needs the Hounsfield Unit
    (HU) for extraction. I've found many different HU scales for human
    body parts. My questions are;

    1. In DICOM tags, there is a value called "RescaleIntercept" what
    exactly it is ? 

    is it an offset of CT dataset ? and if it is for example -1000, so what is
    the real HU of water for -1000 value ?

    

    HUofBone = (double)DicomReader->GetRescaleOffset() + 1200.0;

    boneExtractor->SetInputConnection(Dicomreader->GetOutputPort());

    boneExtractor->SetValue(0, HUofBone);

    

    In the given code, what GetRescaleOffset returns ?  

    

    

    

    

    

    Chasan KIOUTSOUKMOUSTAFA 
    
   
  
  
  

  

  Chasan KIOUTSOUKMOUSTAFA 
  
 


   



 




      
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