99mTc Sestamibi SPECT/CT vs 18F Fluorocholine PET/CT

This study compares two imaging tests — a standard nuclear medicine scan (SPECT/CT with sestamibi) and a newer PET scan (with fluorocholine) — to find overactive parathyroid glands in people with high calcium levels. **You may be eligible if...** - You are suspected to have a parathyroid adenoma (an overactive parathyroid gland causing high calcium) - Your standard sestamibi scan was negative or unclear - Your liver function is within acceptable limits - You can give written consent **You may NOT be eligible if...** - Your initial scan was clearly positive and surgery is already planned - You have liver problems (elevated bilirubin or liver enzymes) Talk to your doctor to see if this trial is right for you.