TextField._height problem when using img src

I’m using css and xml content in a textField. I’ve built a scroller that sets itself based on the textField height (ie its not using lineheight to scroll). I’ve just started using <img> tags to load various images into the content, and when I retreive textField._height, i’m getting ridiculously high height numbers , which of course is causing the scroller to be inaccurate.

Anyone have this problem / found a solution?