If you have any tubes that have JPEG speckling, then you can clean them up nicely before you use the tube in your project.

Before Clean-up




After Clean-up




To clean up your tube, go to Adjust > Add/Remove Noise > Edge Preserving Smooth.  If you're using a version other than PSP8, then the path may be different.




Usually an amount between 1-3 will work nicely (adjust the amount for the image that you are working with).

Then you may want to sharpen the image.  I use Unsharp Mask to sharpen my images.
Adjust > Sharpness > Unsharp Mask:
Radius=1,
Strength=25-50 (or whatever looks best for your tube),
Clipping=0