Rectangle detection on a low contrast image

I have a low contrast image in which I want to detect a rectangle.

I tried a few methods with no success.

Tried Canny filter and some other methods I found in the MATLAB Central.

Below is the .mat file of the image https://drive.google.com/open?id=0B1GIlNbYAqYQVEF3REF4Ny05b1U

Image

Marked ROI image

[Image Analyst]

Why does that red dotted line_not_ indicate success? Also, in your images, what stays the same and what changes? For example, do the intensities of the different regions change? Does the positions change? Does the image rotate? Will you have dramatically different noise levels?