CT scan/ultrasound for TT muscle repair damage after recent surgery.

You should talk to your plastic surgeon about your tummy tuck. Oftentimes, it is quite obvious if the stitch has become unraveled by a physical examination. Essentially, it would look like your “pooch” is back. Have an exam and then see if your doctor recommends further testing. 

As you know 110% is actually not possible.  There is also the chance that a stitch or two popped that may not even be visible on a CT scan.  I am not sure why you would be concerned at this point. 
Do you have pain?Do you have a bulge?Did you hear a pop?
So, although you may get a CT scan that may or may not show a "popped stich", if you don't have any of the above, you may not need/want to do anything anyway.  I would simply follow up with your Plastic Surgeon for a full examination.

It depends on how far out you are from surgery. In the very early post op if you pop a stitch it is hard to tell because everything is swollen. When you get further out like ~3 months it can be pretty obvious if a stitch was popped because you will look poochy in the area where the stitch popped. Did something happen that makes you think a suture popped? In the few patients that this happened to in practice, it was the same thing...all returned to sexual activity before the 4 weeks were up (even though they were advised not to). They felt a pop followed by pain and sure enough once the swelling went away they looked full in their upper abdomen. A CT scan of the abdomen is not something your PS can do in their office. This would be something that is done at an imaging center or hospital. You would need an order to get one from a doctor, so it is best to talk with your PS first. Not sure your insurance would pay for this imaging, so definitely make sure it is something your PS wants before attempting to get one. It is always best to avoid unnecessary out of pocket expenses.