Normally, there are no image quality losses, if you use Muse correctly. Here you find two links, which deal with this issue quite deeply:
If these informations don’t help, please give us
Then we can have a closer look. You may upload these two files to Dropbox or a similar file sharing service and post the download link here.
Additionally, it is better, to use vector images instead of pixel images, whenever possible. Vector images (SVGs) stay crisp and sharp regardless of their actual size.
looks like a pdf