Frequently asked questions about computed tomography

This is an automatically translated article.

The article was professionally consulted by Specialist Doctor I Tran Cong Trinh - Radiologist - Radiology Department - Vinmec Central Park International General Hospital. The doctor has many years of experience in the field of diagnostic imaging.
The method of computed tomography allows accurate assessment of the lesion location in 3D space, thereby providing a good orientation for surgery as well as radiation therapy. This article will answer frequently asked questions about computed tomography.

1. What is tomography?

Computed tomography (CT scan) is a technique that uses X-rays - a type of radiation to shine on the area of ​​the body that needs to be examined, which can be the brain, abdomen, heart, lungs,... After the X-ray Projected into the body, a 2-D or 3-D image is obtained in a cross-sectional layer and projected onto a dedicated computer screen. Doctors can look at the images obtained to detect and diagnose the patient's pathology accurately.

2. Advantages and disadvantages of computed tomography compared to other methods

Advantages:
Computed tomography has the following advantages:
Clear image due to lack of overlap The image resolution is much higher than that of radiographs. Quick capture time, necessary in surveying, evaluating emergency diseases and surveying mobile parts of the body (lungs, heart, liver, intestines...). The high spatial resolution of bone makes it very good for examining bone pathologies. The technique uses X-rays, so it can be used for imaging patients with contraindications to magnetic resonance imaging (Pacemaker placement, metal heart valves, fixed hearing aids, metal relics...). The technique of computed tomography can be applied to a wide range of patients, from people wearing hearing aids, pacemakers,... to people with foreign bodies in their bodies. In addition, CT scanning is also recommended for patients with serious problems related to bones and joints.
Compared with the X-ray method, the computerized tomography technique is modern and gives clearer results because it can capture images of soft tissues, the doctor can clearly see the damage inside. . Usually, this technique takes place very quickly, it only takes 5 - 30 minutes depending on the location.
Disadvantages of computed tomography method:
The doctor's computer tomography method is not applicable to young children and pregnant women, suspected of being pregnant. Because for pregnant women, X-rays that shine into the body will affect the development of the fetus. As for children, experts also warn against performing this technique because X-rays can cause cancer in children, although the rate is very small.
In fact, compared with MRI, tomography has less sharp image resolution of soft tissue structures. Therefore, the ability to detect small lesions is also less.
For injuries in ligaments, cartilage, spinal cord, ... this method will be difficult to detect.
CT scan is difficult to detect and distinguish for organs and damaged areas with the same density.

3. When does the doctor order to use the tomography method?

Computed tomography is indicated in some cases:
For the doctor to diagnose disorders in the muscles and bones, such as bone tumors or fractures. Locate the tumor, blood clot, or infection. Support surgery, biopsy and radiation therapy. Help detect and monitor serious medical conditions of patients such as heart disease, cancer,... Monitor effective treatment process, such as treatment of heart disease, cancer,... Suspicion, imaging to detect internal injuries and internal bleeding.

4. Notes before tomography:

Before going for a tomography scan, you should note a few things as follows:
Clearly inform the health problems you are having If you are pregnant or suspect that you are pregnant, you must notify your doctor for review before surgery. intend to implement this technique. Depending on the part of the body being examined, the doctor will ask the patient to fast before the scan; remove metal objects and jewelry; Dressing and dressing hospital, clinic provided. If the object of medical examination is a child, a parent or relative should accompany to assist when necessary.

5. Does the CT scan have to use contrast? When does computed tomography have additional indications for the use of contrast agents?

Contrast is a drug used in CT scans to clarify damaged tissue so that the doctor can detect and make an accurate diagnosis. This drug is well tolerated. There are a few cases where patients have side effects due to drugs such as vomiting, nausea, itching, hives, red face, fever, ... So if you have a history of allergy to this drug you should report it. with your doctor before the procedure.
However, not all cases are indicated for the use of contrast agents. The doctor will base on each patient's condition to decide whether to use it or not. Note that the use of contrast medium will cost more expensive CT scan than not using.
Currently, Vinmec International General Hospital is equipped with a 640-slice CT scanner TSX - 301C manufactured by Toshiba capable of supporting diagnosis on an area up to 16 cm wide, fast speed allows one rotation of the image. The whole heart can be detected, helping to optimally diagnose coronary, vascular and systemic arteries. In particular, this machine can reduce up to 90% of radiation dose, so it can be taken for pregnant women when indicated.

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