This project is an extension of previous work directed toward the study of noninvasive methods to determine spatial and temporal relationships existing between tissues of clinical interest. The approach involves in vitro modeling of promising systems and the development of prototypes suitable for clinical evaluation. Recent work has focussed mostly on studies directed toward development of a versatile computerized dental radiographic system to produce images which can be subtracted to show small changes in tissue occurring over long intervals of time, and which can be combined in ways permitting synthesis of desired projection or tomosynthetic display of specific slices of the teeth and jaws. Design principles of a new prototype x-ray tube have been established, permitting the generation of any number of focal spots on a planar target with the aid of a computer controlled electron beam. Specifications have been developed to build an intraoral x- ray detector based on solid state CCD technology, proximity coupled to a scintillation screen. Calibration methods and software are developed to control the effects of differential x-ray beam hardening in the quantitation of bone loss. Research efforts continued on the design of a head holder system replacing the use of dental stents to stabilize the projection geometry in film-based radiography. Measurements on a prototype design demonstrated that the use of visual feedback by a closed circuit video system permits patients to position themselves reproducibly to enable subtraction radiography with sagittal as well as frontal projections.