A normal bone density T-Score range is between -1 and +1, according to the National Institutes of Health. The T-score measures the number of standard deviations a patient's medical bone density occurs from that of a healthy 30-year-old adult of the same sex and ethnicity of the patient.
A bone density scan is a diagnostic tool used to determine the amount of mineral matter per square centimeter inside a patient's bones, according to WebMD. Any substantial deviation from normal, either too high or low, can indicate a pathology.
A bone mineral density test is performed by exposing the patient to two X-ray beams, explains NIH Osteoporosis and Related Bone Diseases. The second beam is used to remove the signature caused by soft tissue. Each bone of interest is scanned independently to control radiation dose.