Import and Vectorize LINE Dwgs

I have Toon Boom Studio 4. I am attempting to Import and Vectorize line drawings that I have cleaned up on a drawing board and scanned into a file. Then: right click cel>select Import and Vectorize>from file>Black and white.
The LINE drawing is converted to BRUSH when imported and although the Find Center Line function reverts the drawing to Line, contour infomation is lost or corrupted which requires further clean up. How do you get acurate, clean line drawings into TBS4.

I am mostly working with brushstrokes,rarely working with lines.
But while you are waiting for better answers, why not have a look at this video on the TB cartooning wiki page.

Beat regards

When you import and vectorize it will come in as brush stroke.
If you do not modify the drawing and but then extract center line, you should be able to manipulate it as a line drawing. If you go back to brush however, different data will calculate resulting in a new display of your image.
The best thing to do is to keep it as brush strokes, or to change it to pencil line before any modification and then continue to work in pencil line.

Thanks debbie & ivaar. The comments and vid reinforce my experience of importing drawings into TBS-4. I am not missing something basic or obvious. Very helpful!