Cleanup FileSystem storage files

Hi,

We have a project where we use the FileSystem as the default storage provider for images and documents. We've got about ~20000 files in the FileSystem. We recently deleted a bunch of images and documents from Sitefinity but it doesnt look like the files got deleted from the FileSystem because it still shows the same number of files in the folder. It's using unnecessary disk space - how can we clean up the folder? Is there any code I can run one time to find out which files aren't in use anymore?

Thanks,

Nidhi