Computed tomography (CT) is a radiological examination that uses X-rays to obtain images of the structures under examination (detailed pictures of organs and bones. Cross-sectional and spatial images). The purpose of the examination is to evaluate organ structures and detect possible structural abnormalities. CT enables large areas of the body to be visualised, multidirectional image reconstruction to be carried out and high quality examination results to be obtained (also of mobile organs such as the heart).
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The CTscan is one of the painless and safe examinations for the patient. It is a non-invasive procedure. It is quick and simple. It is, however, subject to certain preparations.
What is a CT scan?
The CT scanner uses X-rays for the examination - the basic part of the apparatus is the X-ray tube and the detectors (they are suspended on opposite sides on a circular rim). The patient is dropped into the CT scanner, lying on a special table. He or she is then positioned between the lamp and the detectors. The X-ray tube generates radiation that penetrates the patient's body and is received by the detectors. The foundation of the image obtained is based on the X-rays and the different ways in which they are attenuated by the various organs of the body.
Important! The detectors can measure the level of attenuation and a cross-section of the body is created on this basis.
The use of tubes with different focal points in CT allows the radiation parameters to be selected according to the type of examination and the patient's physique. The information obtained is then converted into a digital image.
Important! It is possible to obtain three-dimensional reconstructions of the interior of organs that have light (e.g. blood vessels, stomach, intestines). Reconstructions of this type are called multiplanar, 3D or virtual endoscopy.
Course of examination
Prior to the CT scan, the doctor will take a short history, and (this is not the rule) a prepared questionnaire should be completed. In addition, the patient signs a consent form for the examination and administration of the contrast agent. The patient must inform the doctor of the presence of:
- allergies or a previous allergic reaction to the administration of a contrast medium,
- claustrophobia,
- lactation,
- pregnancy,
- susceptibility to bleeding.
Patients with a history of kidney disease and renal insufficiency should inform the doctor before starting the examination. The results of other imaging tests performed, if any, should also be provided.
The patient should be fasting for the CT scan (no solid food should be consumed at least 6 hours before the CT scan, and no liquids for 3 hours). You should also refrain from smoking before the examination.
Important! Persons being treated for chronic diseases (e.g. diabetes) should take their medication on the day of the examination as usual.
Before the examination, the patient is asked to remove any metal ornaments (e.g. earrings, watch, rings). In addition, keys, mobile phone, wallet should also be put away.
You do not need to undress for the examination - only those items of clothing with metal components (e.g. belt buckles, metal buttons, zippers) need to be removed.
Important! Before the CT examination, the patient should empty the urinary bladder.
The patient lies down on a narrow moving table (usually on the back), then the table is slid into an illuminated tunnel. Inside the apparatus, a lamp moves around the patient, which produces X-rays - these pass through the patient's body and allow an area of a particular layer of the patient's body to be obtained on the monitor.
Important! It is very important that the patient lies still during the examination - any movement may interfere with the examination image. For those unable to remain motionless during the examination, sedation or general anaesthesia may be required.
The patient is left alone in the examination room, but is in constant contact with the medical staff. The CT examination lasts from a few tens of seconds to several minutes depending on the type of examination. However, the patient's stay in the laboratory will be longer - this involves, among other things:
- positioning the patient in the CT scanner,
- insertion of an intravenous line,
- administration of the contrast agent,
- carrying out the examination,
- entering the obtained images into the computer.
TheCT examination, as mentioned above, is painless (except for the injection of a syringe with contrast medium into a vein). The examination can be interrupted at any time - there is a connection between the camera chamber and the console, where the staff performing the examination are located. In addition to the cameras, the CT scanner also has a microphone. During the examination, you should inform your doctor immediately if you experience any adverse symptoms (e.g. shortness of breath, dizziness, nausea).
Important! Contrast is sometimes necessary during the examination in order to improve the image and differentiate between structures.
Contrast is a liquid substance that absorbs X-rays to a greater or lesser extent than the surrounding tissues. The type of contrast currently used in CT is iodine contrast agents.
Complications following contrast administration do occur:
- mild (including nausea, vomiting, urticaria),
- moderate (including fainting, profuse vomiting, widespread urticaria),
- severe (including convulsions, pulmonary oedema, shock).
Important! Occasionally, contrast administration causes acute post-contrast nephropathy - acute renal failure in a person with normal renal function prior to contrast administration or significant deterioration of renal function in patients with previously diagnosed chronic renal failure.
During the examination, the patient may be asked to hold their breath (any movement, including breathing, may cause errors in the images obtained).
Flu-like symptoms, arm pain, muscle cramps may occur after the examination.
The result of a CT scan is in the form of a description, sometimes accompanied by photographs.
