Effect of x-ray tube motion on dental radiographic resolution

X-ray tube movement during intraoral radiography is generally discouraged; however, the effects have not been quantified or reported. A portable x-ray tube head was mounted on the horizontal cross-beam of Instron model 1125 universal testing machine. Precise movement from 0 to 25 mm of oscillation was accomplished in increments of 1 mm. Four test objects were imaged during x-, y-, and z-axis movement of the tube head. Pinhole camera and star test pattern images were used to measure focal spot size for each increment of motion. Images of a resolution plate and a section of dry mandible were used to evaluate levels of resolution objectively and subjectively for each increment of motion. Results indicate that the size of the effective focal spot increases predictably with increasing increments of tube motion accompanied by a corresponding loss of resolution. Movement of the tube along the x- and y-axis relative to the plane of the film produced similar losses of resolution and were much greater than loss associated with z-axis movement.