What would need to be written into my sites .htaccess file to "ping" a php file when an image is called ?

So if I type mysite.com/image.jpg into my browser, a file at mysite.com/image.php is ran.

Basically when image.jpg is called image.php should be ran to update the displayed images contents.

Edit: The below bit half works, it gets the images updated by hitting the associated php files but when I try to call the images they don't come show, what gives ?

RewriteEngine on
RewriteRule Nintendo3DS4free.jpg$ Nintendo3DS4free.php [L]

Also, I would like to ask that you keep an eye on this question until it is solved. Oh, and someone previosuly suggested redirect, well... if you take a second to try and understand what I'm asking you'll know thats not what I'm after.