vcode and CPT® code

My biller has been useing the v72.83 code with the CPT® code 93971 and billing it to the company. The reason she's is using it is for pre-op/procedural testing to see if there is a viable Leg Vein that can be used for a Carortid-Endarterectomy. I don't think this is allowable. Are we allowed to bill for this Non-invasive Vascular study with a V code only? She has been billing it w/just the V code, not another dx such as 433.10.

Please help