I added this sentence to the end. I had a question on a shelf recently where both options were given. Although the answer to this Q was to start heparin rather than imaging, I think this is still an important distinction worth noting. I doubt step 2 would give both options as that would be rather unfair but I absolutely would not count it out.
I contemplated putting an image into this card to compare the two imaging techniques but ultimately decided the extra section had plenty of text already.
Source: Other - https://www.atsjournals.org/doi/full/10.1164/ajrccm.161.3.9904067#:~:text=Contrast%2Denhanced%20spiral%20computed%20tomography,acceptable%20to%20physicians%20(7).
Will make decision on other open suggestion