Medical ice pack

I have two ruptured discs in my lower back. The doctor has requested that I use an ice pack to help address the pain while traveling. How do I travel using the ice pack?

My current ice pack was just taken as I went through security

Updates 6/15 * I forgot that I have been doing checked luggage the last few trips. This morning was rushed and with it such a short trip, I forgot about the gel pack as a possible violation. * One person told him if it was medical that it might be ok, but the next one said nope. I can't blame him it was list in one of the faq for TSA. * The gel pack was not frozen. But I had traveled last few trips without it (difference is checked luggage vs carry on!) this I was a little worked up.