Images Not expiring off Disk Netbackup 7.6

Hello

I have noticed that one of our PureDiskVolume deduplication disks has filled up (above 95% water mark). I have expired some old images that are no longer required, I have done this but the space has not been cleaned up. I understand there is another command that needs to be run to reclaim the space but am unsure what command to safely use as I do not want to remove all my other backups on the disk. I only need the images I have expired space re claimed

Hope someone can help

Thanks In advance!