Perhaps you should try some spelling variations:
image preprocessing » image processing (Expand search), images processing (Expand search), data preprocessing (Expand search)
decrease covid » increase covid (Expand search), increased covid (Expand search), disease covid (Expand search)
covid decrease » rapid decrease (Expand search), soil decrease (Expand search), via decrease (Expand search)
decrease image » decrease age (Expand search), decrease intimate (Expand search), decreases immune (Expand search)
in decreased » is decreased (Expand search), in deceased (Expand search), and decreased (Expand search)

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "(( decrease covid decrease image preprocessing ) OR ( decrease in decreased _ decrease ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease covid decrease image preprocessing ) OR ( decrease in decreased _ decrease ))*.