If it is less than 72 hours since they mated it is possible to get the canine equivalent of the morning after pill. If it is later than this then the earliest time at which pregnancy can be determined is about 22-28 days. At this time pregnancy can be detected by ultrasound, a blood test for relaxin (a hormone only produced in pregnant dogs) or palpation of the dog by the vet. X-rays can not be carried out until about 45 days of pregnancy and is normally only carried out to determine the litter size. If an abortion is required then it may be worth considering having your borther’s Akita spayed at the same time unless he is considering breeding from her. Either way, this in no way "taints" any future offspring she might have which are purebred Labrador.