Fine structure of the Panorex image.

The plane of focus free of blur margin, as well as the rate of increase of blur margin both medial and lateral to the plane of focus, has been described in the Panorex panoramic x-ray machine by means of a continuous phantom. The average of readings made at ninety-eight separate film positions yields a focaltrough thickness of 4.3 mm. if a blur margin of 10 per cent of the phantom's film image is accepted, the percentage blur increasing directly with trough thickness. The factor enlargement of objects at the plane of focus is uniform at 1.25 and increases along with percentage blur more rapidly for objects medial to the plane of focus than for objects lateral to it.