What is Computed Tomography? How does it work?

Godfrey Hounsfield first planned the first tomography scan in 1968, and in 1971, he installed the first prototype computed tomography scanner for clinical trials at Atkinson Morley Hospital in Wimbledon, England. Computed tomography technology was used for the first time to separate a normal brain tissue from a diseased brain tissue. By 1975, devices capable of taking computerized tomography of the whole body began to be marketed. Rumor has it that Alan Cormack (1924 - 1998) independently began working on a mathematical technique that would allow the captured images to be put together. Cormak and Hounsfield shared the 1979 Nobel Prize in Medicine and Physiology. This device designed by Kormak company has revolutionized the field of radiology.

MRI is often confused with tomography, but there is a big difference. While magnetic field is used in MRI devices, radiation is used in tomography devices. The tomography device consists of several parts. It shows similarities with the MR device in terms of appearance and working properties. The device has a panel, table and monitor on which x-rays are projected. During viewing, these parts work synchronously.

Computed tomography; It is a radiological imaging method for creating a cross-sectional image of the object examined using X-rays. That is, the part of the X-ray beam that passes the object is detected by the detectors placed in front of the X-ray tube and converted into an image.

Tube detectors are facing. The controlled beam coming out of the tube is passed through the patient's body and collected through detectors.

However, during this irradiation, unlike the x-ray device, the tube and detector are not fixed. It takes images by constantly rotating around the patient.

The most important feature that distinguishes tomography from X-ray is that the attenuation of X-rays passing through a thin section of the body is measured with a detector and an image is created with the help of a computer.

It is not the principle of casting a shadow of an area, that is, the area taken, on the film, as in an X-ray, but a clear display of all organs by taking cross-sectional images of the irradiated area.

The data collected through the detector are evaluated in the computer environment and images are formed.

Today, advanced multi-slice spiral computed tomography is generally used.

In this device, spiral tomographs were used before, the tube and detectors are designed to rotate around the patient and the table on which the patient lies is constantly moving at a predetermined speed.

Spiral tomography was not sufficient to visualize the heart, which is a moving organ.

Later, multi-slice spiral computed tomography was developed. The difference from the old types is that it has detectors that are thinner and in more than one row. Later, the tube movement has been accelerated considerably compared to the old versions. Detectors, which were previously in 4 rows, were made to be 64 or more rows. Thus, the resolution of the images has increased and it has become possible to do with breathing under 20 seconds.

It is known that nearly 10 million people have tomography in Turkey every year. Tomography devices are advanced technological tools that help in imaging for the treatment of many diseases.

Dr. Tamer Tekin