Removal of white background of image (.PNG) imported with Picture cmd?

I have some black\white artwork in .PNG format that i bring into rhino using the picture command and it appears with a white background. I’d like to remove the background and only have the artwork. Is it possible to do in Rhino. If so then how?

Select the picture, got the Material Tab in the object properties, and there are options there for transparency to use the alpha channel…of course on my model that’s got a bunch of pictureframes in it, that’s on by default…?