Get coordinates from VTKBorderWidget

Development
1

Hello,
I have a program where i am loading a DICOM directory and displaying the sagittal 2d image . In that image i am using a VTKBorderWidget to select a particular region and give that region to VTKExtractVOI.
this is my code snippet:

vtkCoordinate* upperRightCoordinate =
                static_cast<vtkBorderRepresentation*>(m_borderwidget_1->GetRepresentation())
                ->GetPosition2Coordinate();
        double* upperRight;
        upperRight = upperRightCoordinate->GetComputedWorldValue(m_renderer);

vtkCoordinate* lowerLeftCoordinate =
                static_cast<vtkBorderRepresentation*>(m_borderwidget_1->GetRepresentation())
                ->GetPositionCoordinate();
        double* lowerLeft;
        lowerLeft = lowerLeftCoordinate->GetComputedWorldValue(m_renderer_mprwin);

Now i cannot set this directly to the extract voi as extracteddata->SetVOI(lowerLeft[0],upperRight[0],lowerLeft[1],upperRight[1],0,number_of_slices);
so i used:

voi[0] = (lowerLeft[0] - imageOrigin[0]) / imageSpacing[0];  // where imageOrigin and imageSpacing are the dicom image origin and spacing

But iam not getting the region inside the VtkBorderwidget