There is a bit of confusion on the terms, because either a coronary CTA (computed tomography angiogram) or a cardiac catheterization will both use angiography (which refers to the imaging technique).
So sometimes people automatically think an angiogram means that a catheter is inserted in the blood vessel. But there are different tests that have angiogram in the name.
A coronary CTA (computed tomography angiogram) is just where contrast die is injected and the vessels and heart are X-rayed as a 3D image. It is not invasive.
A cardiac catheterization CTA on the other hand, is where they insert a catheter into the artery. That is the more invasive test!
I think there is some blur on the names that different doctors use. Some may just say CTA, but mean a catheterization. It would be nice if the names were more clear.
So all 3 tests (calcium score, coronary CTA, or cardiac catheterization) will expose you to some radiation.
The CTA (without catheterization) is not invasive, but you need to get die injected and take a nitroglycerin tablet to expend the vessels, and possibly take some medicine to slow your heart rate down a bit if it is beating too fast. If your resting rate is slow enough, you don’t need that.
The cardiac catheterization is invasive - they stick the catheter through the vessel and guide it to the coronary arteries.
In order of the quality of images you get out of the tests, in order of lowest to highest quality of images - calcium score, coronary CTA, or cardiac catheterization.
Here are some good links to explain the difference between a CTA and a cath.
Sorry, you may already know this, but just wanted to give an explanation for anyone who hears about these tests.