What is the size difference between an ct scan and a ultra sound

I had a ct scan and they found out I have an aneurysm of the aorta it was 2.8cm and not even 2 months later it was 3.2 again it was measured by ct scan then 2mths later I had an ultra sound and the tech. said it was at 3.48cm but she could not tell me how the measurements could be different. She said the ct scan measurments are different than the ultra sound can anyone tell me how they are different ? My doctors said I have a fast growing aneurysm and I need to be tested every 2 or 3 months.

[crwstar]

That is an excellent question. I apologize I can't tell you how they are diffent. I asked a  similar question recently about difference between angiogram and MRA meaurement of annies. Usually, there is a test that may be considered more accurate. It does look like your anuerysm is growning...will you be having surgery if it is considered fast growing? Have you gotten a second opinion? I am asking because it was amazing to me how many different measurements I got from different docs of the pituitary tumor I have.......Hopefully, someone who has experience in the area will come along and answer your question. Have you also posted this on the Neurology board? Sometimes it helps to posted on multiple boards.

All the best.

[desertrat49]

I am surprised that they initially told you have an aneurysm with a 2.8 measurement. That is within the normal range...Where on the aorta is your aneurysm?  I have one on the aortic root area and mine measures 4.2...It has remained that size for four years now since I was diagnosed n June of '05.  I have an echo once a year along with a ct scan w/contrast every year so they are six months apart. The ct scan and Mri are the most precise measuring tests.  Good luck.  I know how worrying all this can be.  I have been in that state for almost 4 years now never knowing what is going on inside my body.  Christine....