CT Angiography vs Cardiac Computed Tomogrpahy (CT) scan

[carolyncox]

What is the difference between a CT Angiography and Cardiac Computed Tomography?

I have had a CT Angiography done on my neck vessels and chest, and now they want me to have a Cardiac Computed tomography to check my coronary arteries.
I am deeply concerned about the number of radiation I have had in a short time, and cant understand why they cant check all these things in the one scan?
Can you please enlighten me before I confirm/decline the appointment.

Thanks,