A text annotation is a sequence of characters permanently added to images before storing.

Autoradiography is a method that uses incorporated radioactive material as the source of the radiation. The image on an x-ray film or nuclear emulsion is recorded by direct contact of the object with photo emulsion. Photographic emulsions have a very high efficiency for beta radiation.

Back projection is a mathematical procedure used to reconstruct CT images. Back Projection is based on the blurring of the x-rays within a projection back along the direction in which they were measured.

Each pixel in a digital image has a bit range, which informs the computer which color (or shade of gray) the pixel will display.

Bone densitometry measures the strength and density of bones. Changes in trabecular bone mineral density (BMD) is an early indicator of change in metabolic function. Bone densitometry measures the amount of calcium in regions of the bones. A bone densitometer is used to determine the risk of developing osteoporosis and can also be used to estimate a patient's risk of fracture.
Bone densitometry methods involve:
Dual energy x-rays (DEXA) or CT scans (Osteo CT or QCT) compare the numerical density of the bone (calculated from the image), with empirical data bases of bone density. DEXA is widely available and has an accuracy between those of QCT and ultrasound.