How do I make UITableViewCell's ImageView a fixed size even when the image is smaller

I have a bunch of images I am using for cell's image views, they are all no bigger than 50x50. e.g. 40x50, 50x32, 20x37 .....

When I load the table view, the text doesn't line up because the width of the images varies. Also I would like small images to appear in the centre as opposed to on the left.

Here is the code I am trying inside my 'cellForRowAtIndexPath' method

cell.imageView.autoresizingMask = ( UIViewAutoresizingNone );
cell.imageView.autoresizesSubviews = NO;
cell.imageView.contentMode = UIViewContentModeCenter;
cell.imageView.bounds = CGRectMake(0, 0, 50, 50);
cell.imageView.frame = CGRectMake(0, 0, 50, 50);
cell.imageView.image = [UIImage imageWithData: imageData];

As you can see I have tried a few things, but none of them work.