Focal plane tomography

In radiography, focal plane tomography is tomography (imaging a single plane, or slice, of an object) by combining multiple images with focus on a plane of interest. In medical imaging, this was the main method of obtaining tomographs until the late-1970s, but has since been largely replaced by for example computed tomography. Yet, it remains in use in for example dental radiography in the form of orthopantomographs of the jaw.

This technique, developed in the 1930s by the radiologist Alessandro Vallebona, proved useful in reducing the problem of superimposition of structures in projectional radiography.

Focal plane tomography generally uses mechanical movement of an X-ray source and film in unison to generate a tomogram using the principles of projective geometry. Synchronizing the movement of the radiation source and detector which are situated in the opposite direction from each other causes structures which are not in the focal plane being studied to blur out.

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