Problem with RewriteCond replace

I'm havian a problem with RewriteCond in Apache. I have URL myurl.com/cache/100x100/filename.jpg and I need to check if the file exists. The problem is that for me is not important this exact path, but different one. I need to check if the file /images/100x100/filename.jpg exists.开发者_如何学Python Is it possible? Right now I have:

RewriteCond %{REQUEST_URI} ^/cache/([0-9x]*)/(.*)$ [NC]
RewriteCond %{REQUEST_FILENAME} !-f

How can I change this to check different file? Is there anything like replace?

In that case, you probably want something like RewriteCond %{DOCUMENT_ROOT}/images/%1/%2 !-f