Q. Illustrate Temporal digital subtraction radiography?

Temporal digital subtraction radiography (SR) is a radiographic technique that enable two radiographs made at different points of time of the same anatomic region to be subtracted resulting in an image of the difference between the two original radiographs.

The resulting substraction image depicts changes in the patient's anatomy such as alveolar mineralization or volume changes during the time between which the two radiographs were made.

SR has had limited utilization in clinical practice because of the difficulty in obtaining reproducible periapical radiographs.