Quantitative computed tomography (QCT) is a medical technique that measures bone mineral density (BMD) using a standard X-ray Computed Tomography (CT) scanner with a calibration standard to convert Hounsfield Units (HU) of the CT image to bone mineral density values.[1] Quantitative CT scans are primarily used to evaluate bone mineral density at the lumbar spine and hip.
In general, solid phantoms placed in a pad under the patient during CT image acquisition are used for calibration. These phantoms contain materials that represent a number of different equivalent bone mineral densities. Usually either Calcium Hydroxyapatite (CaHAP) or Potassium Phosphate (K2HPO4) are used as the reference standard.[2]