I've never heard or used "CTPE", but I'm sure it's just shorthand for a pulmonary embolism protocol chest CT, which is exactly what a CTPA is. CTPA was our term for such a study in residency, and I still use it all the time, but no one else at my current hospital does. On the other hand, I always just say PE or pulmonary embolism, while every else I work with says PTE or pulmonary thromboembolism.
Just whatever you do, don't ask for a "spiral" CT to look for emoblism.