Connecting iMac Mid-2007 to MacBook Air Mid 2012

Hi,

Can I use my iMac (20-inch, Mid 2007) as a second monitor for my MacBook Air (13-inch, Mid 2012)? My MacBook Air would be the main computer and the iMac would be used as a second display with the MacBook Air. If this is possible, what is my process and what do I need to purchase?

I have these ports on my iMac, Mid 2007:

*Ethernet

*FireWire

*USB

*MiniDisplay Port

Photo of my ports:

I also have the option to click on "Detect Displays" on my iMac, Mid 2007.

Thank you!!!