Advantages of CT over other diagnostic methods
- With standard radiography or orthopantomography, a single planar and summation image of the object obtained. With computed tomography, a three-dimensional object thoroughly scanned.
- A regular shot is a static two-dimensional image. It can be viewed on a negatoscope or using the “videography” program, but it is already impossible to look at an object from a different angle or in a different projection – this requires repeated diagnostics. In turn, a 3D image of the teeth is an exact copy of the entire scanned area and, already in the absence of the patient, the specialist can examine the object of interest to him from any angle.
- An x-ray is a summation image in which all parts located in series superimposed on each other. CT is a section of tissue of an object with a thickness from fractions of a millimetre to several millimetres, drawn randomly at a given location.
- When conducting an X-ray examination, projection distortion of an object arises in magnitude or configuration, which can lead to errors in image interpretation. When computed tomography, the objective is scanned almost “one to one”, which eliminates this type of distortion in the process of reconstructing a three-dimensional image and obtaining a slice.
Equipment for CT scans
Technically, every modern tomograph consists of a three-dimensional scanner and a computer. A standard general medical scanner (tomograph) is a table on which the patient located, and a gantry is a scanning device in the form of a ring through which the table with the patient moves. Fourth-generation machines already carry up to one and a half thousand detectors in the aperture, and the most modern spiral ones – 5000 and more.
Spiral and multislice CT of teeth
With a spiral 3D tooth image, it is no longer a series of scans at different levels, but one run of the cut in a spiral with a specific pitch of feeding the table into the aperture.
The pinnacle of the development of spiral tomography was the emergence of multislice CT. In this case, not one spiral cut made, but immediately 4, 16 or more with a detector size of 0.5 mm (respectively, a resolution of 2 pairs of lines per mm).
Create 3D teeth image
The process is as follows:
- the emitter works continuously, information is read from the sensor several times per second;
- the received data processed in a computer, and a virtual three-dimensional (3D) model of the scanned area restored;
- three-dimensional reform is “cut” into layers in the form of axial sections of a certain thickness;
- each layer saved in the computer memory as a file in the DICOM format.
Despite the broadest diagnostic possibilities, until recently, 3D dental images as a diagnostic method were rarely used in dentistry. That was mostly due to the general not too high diagnostic requests of dentists, and image quality insufficient for the needs of therapeutic dentistry.