Computed tomography (CT) of the colon using liquid or gas with virtual endoscopy

This is an automatically translated article.

The article is expertly consulted by Master, Doctor Nguyen Hong Hai - Doctor of Radiology - Department of Diagnostic Imaging and Nuclear Medicine - Vinmec Times City International General Hospital.
A colonoscopy is a technique that uses X-rays through a scanner to visualize the structure of the colon. Colonography scanning technique gives clear and detailed images. There is also the ability to visualize the colon from cross-sections, hence the name virtual colonoscopy.

1. Overview of CT Colonography

Computerized tomography (CT) is an imaging technique that uses high-intensity x-rays to scan areas of the body. A CT colonography or computed tomography colonoscopy is a multi-slice machine used to look at images of the rectum and colon or large intestine. Unlike colonoscopy, colonoscopy is a non-invasive method, but the images and information are similar. For this reason, a colonoscopy is also called a virtual colonoscopy.
The multi-slice computed tomography machine consists of many parts, the most important of which is the X-ray chamber which is designed in the form of a giant round block. The patient lies on the x-ray table and is pushed into the imaging chamber with the part to be examined under the scanner emitting X-rays. The scanner inside the x-ray chamber will rotate continuously at high speed during the production process. X-ray beam. Different parts of the body with different densities corresponding to each type of tissue will have different density and reproduce images with different colors from white to gray to black.

Colon polyps or colon polyps are the two most commonly used conditions for colonography. Colon wall polyps appear when there is an abnormal proliferation of the lining of the colon, which may be caused by genetic abnormalities. Usually, colon polyps are benign lesions, but they can still progress to colon cancer.
If you are over 50 years old, admitted to the hospital because of bloody stools, disordered bowel habits, weight loss, pale skin and mucous membranes, the doctor who suspects a colorectal malignancy may be diagnosed with colorectal cancer. to undergo a colonoscopy.
In addition, a prominent advantage of colonoscopy is that it is safe and minimally invasive, so colonoscopy can be indicated as an alternative to colonoscopy in patients with colonoscopy. elderly or frail patients with chronic medical conditions.

2. The procedure for performing a colon scan

Although CT colonography is quite safe and has few side effects, it needs to be performed correctly to provide good image quality as well as create comfort for the patient during the procedure. In general, each medical facility will have its own regulations on performing a colonoscopy, but still must follow the following main steps:
Use muscle relaxants to reduce colon spasms to facilitate the get a good picture. Contrast-enhanced tomography may also be indicated. In this case, the patient will be prescribed oral contrast a few days before the procedure. Instruct the patient to lie on the table in a supine, supine, or prone position. Using straps to fix the knee and two legs to help the patient fix the posture during the shooting process, avoid image noise.

Insert a small tube from the anus into the rectum to inflate the colonic lumen. The amount of air injected has the effect of dilating the colonic lumen, facilitating observation and detection of polypoid lesions in the colon. When inflated, the person may feel bloated and want to defecate or pass gas. This is a normal response of the body, the patient should not be too worried. Move the table until the patient is in the room. Respiration should be performed according to the technician's instructions. The patient needs to hold their breath for about 15 seconds before moving or changing positions. The scanner emits rays to take and record pictures of the colon. In addition, these images are also 3D-rendered to create a colonoscopy-like image. After the scan is over, the inflatable tube is removed and the patient is taken out of the colonoscopy room. Patients can eat and drink and return to normal activities immediately after the scan. The feeling of bloating will disappear gradually, the patient may fart many times after the end of the scan. For women who are breastfeeding, any milk produced within 24 hours of the scan should be discarded. Therefore, to facilitate child care, before going to a colonoscopy, breast milk should be expressed and stored enough for a newborn's daily needs. The colonoscopy takes about 10 to 30 minutes.

3. What preparation is needed before a colonoscopy?

As a rule, patients will be guided and advised on what to do before performing a colonoscopy to ensure good image quality and safety of the technique. Some things to keep in mind include:
Adhere to a special diet for a few days before the procedure Before a colonoscopy, enema or laxatives are needed to clear the bowel. Laxatives can make people tired in some cases as a side effect of diarrhea. With the indication for a colonoscopy with contrast, the patient will be instructed to take contrast two days before the scan. The main role of the contrast agent is to create a contrast that helps to create a more accurate image of the colon. In some cases, contrast media may be administered intravenously. At that time, the patient needs to be examined more closely to rule out contraindications and sometimes have to stop using some of the previous drugs.

On the day of the colonoscopy appointment, the patient will be told to fast for about 4 hours before. A colonoscopy is a technique that uses X-rays through a scanner to visualize the structure of the colon. However, in order to have the most realistic and clear image, the patient needs to choose a reputable medical facility or hospital to perform.
At Vinmec International General Hospital, the CT colonography procedure is performed by a team of highly qualified and experienced doctors in the field of diagnostic imaging, along with equipment, Modern machines for accurate and fast results.
Master, Doctor Nguyen Hong Hai graduated with a Master's degree in Diagnostic Imaging at Hanoi Medical University with strengths in diagnosing breast and thyroid cancer. Currently, Dr. Hai is working at the Department of Diagnostic Imaging, Vinmec Times City International Hospital.
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