Am I measuring this right ?

Did you make these measurements or were they already on the picture? I think it is very challenging to measure a 3-dimensional object from a 2-dimensional picture, especially shaped like an aorta and expanding/contracting like an aorta does 🙂 I would not have much faith in any measurement I made myself. Additionally, there is some convention that is used in the medical literature when talking about "size", so I'd guess you have to know that as well.

If the picture already had the measurements dropped in, then I'd have more faith. Even then, if there's a dimension you are concerned about, it's reasonable to ask your doctor. At least a small part of their job is to help you through this (or at least I believe that and luckily have doctors that believe it too I think).

There is information out there on how they use CT to measure aortas. If it's mostly a mental exercise, in your place I'd ask ChatGPT for a reference and dig in.

Good luck! This condition is hard to not think about. I'm two years after diagnosis and I don't think about it as much as I did at first, but it's "always" on my mind.

We measured on our own from a still image, as my cardiologist is still on vacation. It’s actually not too difficult with the program included (eUnity). My uncertainty was about the exact location of aortic root. Nonetheless, I’m pretty confident in the 10.1 length obtained +or - 1.0 cm. The “hinge” points appear to be at 11.5 and 12.5 cm ( sharp increases in risk profile) from the article, so I feel fortunate. I will verify with cardiologist upon return from vacation.
Best wishes to all on this evolving journey.