使用WPF图像控件渲染时，大小约为11MB的图像文件会占用大量内存

When i try to set the Source of WPF Image to a Image file that is ~11MB size and Shot in 14 MeagaPixcel Camera, the memory shoots up to around 170 MB when the image is rendered on the screen and the memory also never comes down after Rendering. If i try to do the same using .Net 2.0 Picturebox control the memory utilized is only .5MB to 1MB. Logically if the file size of an image is 11MB then it should at the maximum occupy only 11MB while rendering right? What is the cause of such behaviour in WPF? and is there any way to dispose the extra junk of memory after the rendering is compeleted on the screen?When i try to set the Source of WPF Image to a