Computer Tomography
10 questions about CT
What is CT?
Computer tomography — is method of research, obtaining images of internal organs, bones, joints, brain. The method is based on measurement of X-rays passing through the human body.
How does CT differ from conventional radiography?
Unlike routine radiography
- CT produces cross-sectional images (as if the sausage cut into thin slices) and eliminates the imposition of images of various structures to each other
- Sensitivity of CT is at least 10 times higher.
What is multislice computed tomography (MSCT)?
Since the first CT scanners their design for high-precision images was continuously improved. These types of structures are called generations. According to the number of detectors spiral tomography is divided into singledetector and multidetector.
Multidetector (multilayer / multispiral) technology in practice has a significant advantage compared with 1-spiral. Since it allows to obtain a greater number of images that the necessary data for the unit time, and hence a larger volume can be investigated in a short time. It combines high coverage volume and speed of scanning without losing image quality.
What is waiting for a patient who has come to CT?
Technically it looks as the patient is placed on the table. He remains in a room along. The staff goes into the adjacent room (in the wall separating them has a window) to communicate with patients through a microphone. Table «drives» into the «ring» of a computer tomograph. The research is carried out. The patient hears the slight noise. There is No other discomfort.
Where is radiation dose more at CT or at conventional radiography?
The dose at CT is several times higher and it depends on the volume of the study.
Does the organ that is not visible in the picture receive the exposure?
Organs that are exposed by direct X-ray beam and are recorded on the pictures get the main part of the dose. And adjacent organs receive scattered radiation and, therefore, a smaller dose. The dose depends on the distance to the tissue are exposed by direct beam.
Is there any difference between a radiation dose in children and adults?
Yes, dose differs. For children, the dose will be higher for the same parameters of research that for adult. Since size of a child is less than of an adult, the body weakens fewer amounts of X-rays. Therefore, the dose got is higher by 2-3 times. To avoid this scanners are equipped with special pediatric study modes.
Can CT be made to pregnant women?
Usually pregnant women should not be performed this study, given the high dose and the potential risk to the fetus. The study is possible for emergencies and presented informed consent of the pregnant woman.
What are the consequences of CT to the fetus?
The effects depend on what stage of pregnancy studied and what was the dose. During the first 2 weeks after conception radiation acts on the fruit on the principle «all or nothing»: either abortion takes place, or no effect and pregnancy proceeds without consequences.
After the first 14 days during the first trimester radiation exposure carries a risk of birth defects or mental retardation. For doses of 250 mGy the risk is ≤0,1% at 1 mGy.
After the first trimester radiation increases the risk of cancer in children, it is 0, 07-0, 88%, depending on the dose and term of pregnancy.
The lowest dose fetus receives, if mothers is performed CT of the head. The closer the examinee body is to the fetus, the higher the dose of an unborn child. Even if the mother’s pelvic area closed by special apron, it only protects against radiation scanner, but not against the radiation propagating through the body.
Does a person who is in the room with the MRI receive the radiation dose?
Yes, inside the room in which the scanner is set there is a large dose of scattered radiation. Therefore, relatives and staff are asked to go to a separate screened room. So the risk of exposure is eliminated.