CT angiography is CT with contrast which is tailored for specific blood vessels. Every CT angiography is CT with contrast, but not every CT with contrast is CT angiography.
The CT contrast protocol varies for different procedures in terms of injection rates of contrast, slice thickness, the time duration after which the acquisition is made and the number of phases to be taken.
For example, if were to do CT pulmonary angiography, the acquisition would be done with minimal delay so that pulmonary arterial tree is maximally opacified and pulmonary veins have not yet opacified (pathway of contrast from peripheral cannulated vein -SVC -RA- RV- PA- PV- LA -LV- Aorta)