[Derrick Perrin]

You are taking something that is interlaced, and then are deinterlacing it. When you are putting it on a NTSC DVD you are then taking the deinterlaced image and reinterlacing it. The conversion to and from the deinterlaced image will create these issues.

Since you are starting with a interlaced image, and your final product will be interlaced, you should not worry about changing the format.