Perhaps you should try some spelling variations:
radiofrequency dischargess » radiofrequency discharges, radiofrequency images
frequency discharges » frequency changes
radiofrequency mass » radiofrequency images, radiofrequency based, radiofrequency laser

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((((radiofrequency dischargess) OR (radiofrequency mass))) OR (frequency discharges)).
• Adding a wildcard symbol may retrieve word variants: ((((radiofrequency dischargess) or (radiofrequency mass))) or (frequency discharges))*.