Tomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in radiology, archaeology, biology, geophysics, oceanography, materials science, astrophysics and other sciences. In most cases it is based on the mathematical procedure called tomographic reconstruction. The word was derived from the Greek word tomos which means "part" or "section", representing the idea of "a section", "a slice" or "a cutting". A tomography of several sections of the body is known as a polytomography.
In conventional medical dental X-ray tomography, clinical staff make a sectional image through a body by moving an X-ray source and the film in opposite directions during the exposure. Consequently, structures in the focal plane appear sharper, while structures in other planes appear blurred. By modifying the direction and extent of the movement, operators can select different focal planes which contain the structures of interest. Before the advent of more modern computer-assisted techniques, this technique, developed in the 1930s by the radiologist Alessandro Vallebona, proved useful in reducing the problem of superimposition of structures in projectional (shadow) radiography.
Cone beam computerized tomography (CBCT) increasingly has become the newest technology for orthodontists to use in diagnosing complicated oral health problems.
Reporting on four new CBCT systems in the December issue of the Journal of Orthodontics are J. Martin Palomo and Mark Hans from the department of orthodontics at the Case Western Reserve University School of Dental Medicine and C.H. Kau and S. Richmond from the department of dental health and biological sciences at the University of Wales' College of Medicine.
"The long awaited incorporation of the third dimension to our radiographic records is now a reality," the researchers said, adding "There is still room for improvements; however the CBCT technology appears to be here to stay."
The researchers report, "The future in orthodontic imaging seems exciting as we discover new frontiers, and as the paradigm in dentistry shifts from landmarks, lines, distances and angles to surfaces, areas and volumes." They also added that "Orthodontists are beginning to appreciate the advantages that the third dimension gives to clinical diagnosis, treatment planning and patient education."