Ultra sound of breast sonogram complete 76641

Hi
We need a help that we are billing the new CPT® code 76641 complete we have billed the Amerigroup has denying the claim stating as Submit the claim with 50 modifier we billed in a way like 76641 LT and 76641 RT but amerigroup denying like submit with 50 modifier please advise whether 50 modifier is allowed for 76641 also what are the covered dx code for 76641.
Braddy