What is a CT scan?
Computed Tomography is a medical imaging technique that has many applications in diagnostic, research and therapeutic sciences. Computer and rotary X-ray machines are used to create cross-sectional images of the body in computer tomography (CT or CAT scan). These images provide more accurate information than conventional X-ray images. They can show soft tissues, blood vessels and bones in different parts of the body.
In CT scans, the body or organs or any body from which the scan is performed is scanned layer by layer, these images are taken in two dimensions that by placing these 2D images together, a 3D image is made that using these images doctors can see the inner parts of the scanned body or body. During the CT scan, while the inner part of the device rotates and takes a series of X-rays from different angles, it lay in a device similar to the tunnel. These images are then sent to the computer, where they are combined and create images of incisions or body sections. They may also be combined to produce a 3D image of a specific area of the body.
CT Scan shows images of different cross sections at desired depths of the body. In conventional radiography, depth information was lost. On the other hand, it could not distinguish between soft tissues. Naturally, little information about the density of tissues was not easily available. In conventional journalism, the first problem, i.e. imaging from an arbitrary juncture, was solved, but computerized cross-sectionalism solved two other problems of conventional radiography. This means that it has the sensitivity needed to differentiate between soft tissues, and also gives little information about the amount of weakening (caused by the passage of radiation through the tissues). However, in this method, the resolution power is not improved and only the unwanted parts become blurrier.
History of CT scan:
Before explaining more comprehensively about CT Scan, it is necessary to mention a history of X-ray tubes. X-rays were discovered by William Roentgen in 1895. At that time, various scientists were investigating the movement of electrons using a glass tube called the Crookes Tube. Roentgen wanted to depict the function of electrons, so he wrapped his crocs tube with black photographic paper. When he started the experiment, he realized that the black photography page was covered with fluorescent material. This was completely unexpected because there was no visible light in the room so that the action had been caused by it, and also the tube crocs had not emitted a visible light. With further research, Roentgen found that truly some kind of invisible light is produced by Crookes Tube and can penetrate various materials such as wood, aluminum or human skin. This experiment became an introduction and a start to the construction of different generations of CT scans in the future.
CT scan is a method of combining the use of conventional tomography (cross-sectionography) with computer processing. X-rays are used in CT scan imaging. Of course, the dose used in this method is very high and structural differences such as the use of the movement of the X-ray manufacturer lamp (CT scan tube) or the movement of the detector, as well as sometimes the cyclic detectors around the patient and … With a normal radiography, it has a normal radiography.
The EMI brain scanner, installed at Atkinson Morley Hospital, Wimbledon in 1971, by EMI, Hayes, Middlesex is the world’s first commercial CT scanner installed. This brain scanner, designed by Godfrey Hunsfield at EMI, was the first production model to conduct the first tests on patients in 1971. This scan was created as a major imaging technology, especially for the brain. The arrival of CT scans into medical equipment was a great and unforgettable success, so that by 1977, 1,130 CT scanners were installed worldwide. This method remains common and is one of the world’s leading medical imaging providers, however after CT scans newer technologies such as magnetic resonance imaging (MRI) are now used for many diagnostic tasks previously devoted to CT.
The mathematical foundations of computerized mathematics date back to the early 20th century. The practical application of this method was founded in the 1960s. In 1963, Alan Kermak of Tufts University was one of the people who first proposed the theory of a CT scan system. But practically the first commercial scanner was carried out in 1972 by Godfrey Hawnsfield of the EMI Laboratory in England.
The Hounsfield Units unit, named after Hansfield, is a unit used in computer journalism, briefly represented by HU, named in honor of Godfrey Hawnsfield. Due to efforts made by Kermak and Hawnsfield to invent the CT scan system, they were awarded the Nobel Prize in Medicine in 1979.
In the case of reviewing the history of CT scanners, the evolution of these systems can be investigated as seven different generations of these devices.
Why is a CT scan done? Applications of CT scan:
Currently, more than 75 million CT scans are performed annually in the United States. According to one of the most reputable American journals, 2% of cancers (malignant type) are due to high doses used in CT scans. The combination of PET and CT, known as PET/CT, is a new method in which anatomical information that can be detected from CT scan images is combined with metabolic information (using pet scan images) related to function and components and is a desirable method, especially in the study of tumors. It is important to note that high dose of CT is not necessary in this method. This method is used 85% in the study of tumors (diagnosis of malignant cells from benign, accurate observation of the progression of cancer cells and evaluation of response to treatment and radiotherapy), 10% in neurology, 5% in heart studies.
CT scan has many applications, especially for diagnosis of diseases and evaluation of injuries is very suitable. This medical imaging method can help your doctor to:
- Diagnoses infections, muscle disorders and bone fractures
- Determine the location of masses and tumors (including cancer)
- Study blood vessels and other internal structures
- Assess the extent of internal damage and internal bleeding
- Guide surgeries and biopsies
- Monitor the effectiveness of treatments for some medical conditions, including cancer and heart disease, pulmonary nodules and liver mass.
Medical imaging with CT scan is almost noninvasive and can be done quickly.
The main applications of the CT scanner are as follows:
- Neck CT Scan
- Brain CT Scan (Head CT Scan)
- CT scan of sinuses
- Lung CT Scan
- Abdominal CT scan
- CT scan of the spine
- Trauma CT Scan
- Cardiac CT Scan
- Vascular CT Scan
- Knee CT scan
- Breast CT scan
How is a CT scan done?
Computed Tomography scan is one of the medical imaging modalities used to create cross-sectional or shear images of the body by computer using X-ray rotation devices.
CT scan works by sending several X-ray beams at different angles, so that by irradiating these rays to the patient’s body a 3D image is formed by a computer.
Images provide more accurate information than normal X-ray images, they can show soft tissues, blood vessels and bones in different parts of the body.
In fact, computerized tomography scans or CT scans combine a series of X-ray images taken from different angles around a person’s body and use a computer to create cross-sectional or shear images of bones, blood vessels and soft tissues such as lungs and brains in the body.
CT scan technology in continuation of radiology pathway caused the medical and treatment pathways to change dramatically. Using this method, doctors were able to easily see diseases that were often seen in surgery or autopsies in the past and to treat and diagnose more easily and quickly.
The increasing progress of CT scanners, with the passage of different generations of these devices, has been such that they can provide images with cuts less than one millimeter away from the human body.
In general, CT scan is performed in two ways without injection and by injection of contrast agent, according to the doctor’s diagnosis, a special substance known as contrast agent may be given to the patient in order to detect different parts of the body more clearly in X-ray images. Due to its nature, contrast agent blocks X-rays in itself, causing its image to be seen white on CT scan images, making the organ given to it completely recognizable from other organs, such as the intestines, blood vessels or other organs examined. Depending on the part of the body that is examined, the patient may need to drink a liquid containing contrast agent. It may also be necessary to administer contrast agent by injection into the arm or anus through the right intestine. If your doctor intends to use contrast agent, he or she may ask you to take a 9-6 hour before a CT scan.
Preparing for CT scan:
When performing a CT scan, the patient is asked to wear a hospital uniform (gun) and remove metal objects if they are separated and scan and deliver them outside the room. Because metal can interfere with CT scan images as well as in CT scan results. These items can include jewellery, glasses and dentures. Then, the expert of the CT scan machine, or the operator of the device, asks the patient to lie on the bed of the device, until the patient’s preparation is completed by the expert, the expert exits the scan room and goes to the control room so that they can start the scan, during the whole time the CT scan operator has full nobility to the patient and can see the patient’s movement and even hear the patient’s voice.
At the time of starting the scan, the patient is slowly directed into the cavity (gantry) of the CT scan device by the bed on which he is lying, the X-ray machine begins to rotate around the patient and in practice the patient’s scan begins. In each gantry rotation, countless images are produced depending on the settings and type of scan of the thin incisions of the patient’s body. During the scan, the patient hears the sound of rotation and beeps related to X-ray radiation (expos). At the same time, the patient’s bed moves in or out of the gantry based on the scanning stage or the type of scan a few millimetres to perform the scan properly. The whole process from the patient’s arrival in the scan room to the exit may take between 10 minutes and even an hour.
A very important point that the operator may ask the patient to do when performing the scan is the lack of movement during the scan. During the scan with CT, it is very important that the patient is motionless because movement can lead to blurring of images, which in some cases requires repeating the scan and receiving a larger dose of radiation. The device operator may also ask you to hold your breath for a short period of time during the scan to prevent the chest from going up and down. If a scan of a young child is needed, your doctor may recommend sedatives to prevent the baby from moving.
After completing the CT scan, the images will be sent to the radiologist for examination.
What do CT scan results mean?
If the radiologist does not see tumors, blood clots, fractures or other abnormalities in the images, the CT scan results are considered normal. If any abnormalities are detected during CT scan, depending on the type of abnormality found, you may need further tests or treatments.
Does CT scan have complications?
As mentioned above, the basis of CT scan is X-ray and during CT scan the patient will be exposed to ionized radiation and X-rays. This amount of radiation is greater than the amount of radiation you received from the X-ray of the radiology device, which is why more detailed and accurate information is obtained in the CT scan.
So far, long-term effects and damages have not been shown from CT scans, but there is very little chance of an increased risk of cancer. But we need to be careful about what we get for these small risks, CT scans give us many advantages, so we can ignore the mentioned risks. Usually, physicians as well as medical imaging centers use as little radiation as possible to determine and identify the medical information they need.
Various companies are active in the production of CT scanners around the world, one of the competitive advantages of these companies is the production of more up-to-date devices with less radiation than older models, in these devices they use techniques and technologies that require less radiation.