[Dcmlib] GetZSpacing in Varian Dicom RT dose files

["Piotr Kamiński"]

Hello

File::GetZSpacing returns 0 when reading from a Varian Eclipse DICOM RT DOSE file when you export a calculated dose cube from. 

But there is another way of guessing the Z-Spacing there - you can get it from the Grid Frame Offset Vector field (0x3004,0x000c), which usually looks like
0.0\2.0\4.0...

Maybe you will consider adding a fix to the GetZSpacing function

the following works in the stable version but not in the CVS version

float dummy, z_spacing;
ValEntry *vr = ff->GetValEntry(0x3004,0x000c);
sscanf(vr->GetValue().c_str(),"%f\\%f",&dummy,&z_spacing);

Thanks
Piotr Kaminski