Find a jQuery dialog by its title

I previously created a jQuery dialog like this:

            dialog.dialog({
                title: 'Hello',
                closeOnEscape: true,
                width: "auto",
                maxWidth: "500",
                close: function(event, ui) { dialog.remove(); }
            });

Now I need to check if some dialog with the title 'Hello' exists.

How can I do that?

Thanks.