Generality
CT with contrast is computerized axial tomography that uses a contrast medium to create detailed images relating to blood vessels, lymph nodes and parenchyma.
Thanks to contrast CT, doctors can diagnose not only conditions, such as pulmonary embolism, deep vein thrombosis, pancreatitis or acute appendicitis, but also to identify the stage of a neoplasm, dependent malformations of blood vessels and alterations of the parenchyma (fibrosis and cirrhosis).
With a total duration of about 35 minutes, the contrast CT provides for a certain preparation and, for its correct execution, imposes maximum immobility on the patient.
The risks of CT with contrast are connected to the dose of ionizing radiation, to which the patient is exposed during the examination, and to the contrast medium, which in some individuals causes an allergic reaction.
Contraindicated in case of pregnancy, obesity, renal insufficiency and diabetes, the CT with contrast provides excellent quality images, which allows to make very precise diagnoses.
What is the TAC With Contrast?
CT with contrast is computerized axial tomography that uses a contrast medium to highlight blood vessels, lymph nodes and parenchyma in greater detail.
Just like any other type of CT scan, contrast CT is a radiology procedure; this implies that its execution and the interpretation of the results deriving from it are up to a radiologist (or simply a radiologist ).
CT with contrast is also known as TAC with contrast medium .
To understand: what are parenchyma?
In medicine, the term " parenchyma " identifies the specific functional tissue of an organ with a compact structure, such as the liver, kidney, brain, lung, pancreas or thyroid.
In light of this, the contrast CT allows to highlight and study the particularities of the organs characterized by parenchyma.
Short review of what the TAC is
The CT scan, or computerized axial tomography, is a diagnostic procedure of radiology, which uses ionizing radiation ( X-rays ), to create extremely detailed three-dimensional images of specific anatomical areas of the body (brain, bones, blood vessels, abdominal organs, organs thoracic, respiratory tract, etc.).
The TAC equipment includes:
- The large donut-shaped scan unit, called a gantry . It is the radioactive source;
- The generator;
- The support on which to place the patient. Generally, it is a sliding bed;
- An electronic processor;
- A command console for displaying three-dimensional images;
- A system for recording the acquired data.
Although it is a normally painless exam (only in the variant with contrast it is annoying, due to the administration of the contrast medium), the TAC is among the minimally invasive diagnostic procedures, since the dose of ionizing radiation, to which the patient is exposed, it is considerable.
Differences between conventional CT and contrast-based CT
The CT with contrast differs from the conventional TAC (ie the CT without contrast medium ) from several points of view: first of all, it captures details that the conventional TAC is not able to display; secondly, it requires a different preparation; finally, it includes an additional procedural step: the administration of the contrast agent in the patient.
Indications
Doctors use CT with contrast when they want to analyze in detail the arteries, veins and lymph nodes, and when they want to collect images rich in details regarding the parenchymal organs, such as for example the liver, kidneys, lungs or brain.
Did you know that ...
The angioTAC is a particular variant of the CT with contrast, which allows to study the blood circulation in various districts of the body - including neck, upper limbs and lower limbs - and in various organs - including encephalon, lungs, liver, heart, kidneys, pelvic intestine, bladder etc.
When is it useful?
CT with contrast is useful for the diagnosis of:
- Pulmonary embolism;
- Deep venous thrombosis;
- Aneurysm of the aorta (thoracic aortic aneurysm and abdominal aortic aneurysm);
- Pancreatitis;
- Pseudocyst of the pancreas;
- Pancreatic cancer (or pancreatic cancer);
- Diverticulitis;
- Acute appendicitis;
- Infarct of the omentum;
- Renal cell carcinoma.
The contrast CT scan also supports the identification of congenital or acquired abnormalities of blood vessels, the display of parenchymal alteration phenomena known as fibrosis and cirrhosis, and the definition of a neoplasm stage .
Preparation
Suitability of the patient for CT Scan With Contrast: what should the doctor know?
Before being able to prescribe contrast CT, the doctor needs to know directly from the patient if:
- He suffers from some kind of allergy . Particularly important is iodine allergy, as the latter is the chemical element at the base of most of the contrast means used for the exam in question;
- He is taking drugs at that time;
- He suffered from some particular disturbance in the last period;
- You suffer from some heart disease, diabetes, asthma or some kidney disease or thyroid disease ;
- He suffers from claustrophobia ;
- If you are a woman, you are either suspected of being pregnant .
All this information is essential to establish the patient 's suitability for an examination as a contrast CT scan.
Preparation for CT Scan with Contrast in case of eligibility for the exam
In case of suitability for the TAC with contrast, in preparation for the latter, the patient must:
- Present yourself for examination without jewelry or clothing with metal parts, as these could interfere with the proper functioning of the diagnostic equipment.
In the event that the patient does not comply with this rule, he will be asked to do so just before the procedure begins.
- Go to the full fasting exam for at least 6-8 hours. This means that, if the contrast TAC is scheduled on the morning of a certain day, the last meal must be the dinner of the previous evening.
Failure to comply with this rule will cause the diagnostic examination to be postponed to another date.
Countermeasures in case of Allergy to Contrast Media?
For people with a proven allergy to the contrast agent used in the examination, the solution to this problem is to take appropriate steroidal drugs with an antiallergic effect, approximately 12 hours after the contrast CT scan.
Delayed intake of these drugs is a reason to postpone the diagnostic examination to another date.
Procedure
Preliminary phase
Just before the contrast CT scan begins, a medical staff member will invite the patient to:
- Respond to a questionnaire related to your medical history,
- Wear a special coat instead of your clothes and
- If you have not done so at home, deprive yourself of all jewelry (eg earrings) and other similar metal objects (eg piercings) until the end of the examination.
At the end of this, therefore, it will subject it to a quick measurement of pressure and temperature, and inform it of the importance it has, during the contrast TAC, its immobility inside the instrument.
Important note on immobility
During the CT scan with contrast (as in all other variants of the CT scan), the invitation to complete immobility also includes the retention of the breath, since even the slightest movements, deriving from the respiratory act, can distort the results of the examination .
Patient accommodation phase
At the conclusion of the preliminary phase, some members of the medical staff will help the patient to position himself, with his arms extended behind his head, on the sliding bed, which will later be used to introduce it and place it inside the so-called gantry .
To ensure maximum patient comfort, the medical staff will provide a pillow for the head, a blanket and a pair of ear plugs (the use of which is justified by the intense noise emitted by the instrument, when it is in operation).
Administration of the Contrast Medium
Once he is relaxed and comfortable on the sliding bed, the patient will be ready for the administration of the contrast medium ; to practice the administration will be, with the collaboration of a professional nurse, the radiologist who will carry out the examination and will interpret the results.
Once administered, the contrast medium will take a few minutes to be distributed in the various anatomical districts of the human body.
CONTRACT MEDIUM: WHAT DOES IT CONTAIN?
As previously announced, the contrast medium used for the contrast CT is generally iodine based ( iodinated contrast medium ).
Did you know that ...
During radiological examinations, contrast media are substances used to modify the absorption of X-rays, in order to make the anatomical area where they wedge more stand out, with respect to what is around it.
ROUTES OF ADMINISTRATION
During a CT scan with contrast, the administration of the contrast medium can be done by mouth (therefore ingestion), by injection (with syringe or automatic pump) or by enema (enema).
Image creation phase
After the time necessary for the contrast medium to spread where it is needed, the following will follow:
- The introduction of the patient into the gantry,
- The transfer of the entire medical staff to a next room, which houses the control console of the entire equipment, e
- The lighting of the gantry . With this last step, the creation of images related to the anatomy section of interest and their acquisition in the console will begin.
It is important to point out that the patient will be able to communicate with the medical staff at any time during the diagnostic procedure, as there is a loudspeaker in the room ; this communication system was designed to give the patient the possibility to report any sudden problems to the medical staff, developed during the CT scan with contrast.
Final phase
Once the useful images for a diagnostic evaluation have been collected, the radiologist will stop the scan and order his staff members to extract the patient from the gantry .
Once the patient has risen from the sliding bed and covered, he can already return home and to his daily activities, unless otherwise indicated by the radiologist.
What feelings does the patient feel during CT with contrast?
- If the administration of the contrast medium is by the oral route, the patient will experience an unpleasant taste in the mouth, once the substance necessary for the examination has been ingested.
- If the administration of the contrast medium is done by injection, the patient will feel a slight sense of discomfort, when the doctor introduces the needle of the syringe or the automatic pump, and most likely a strange metallic taste in the mouth .
- If the administration of the contrast medium will take place via enema (enema), the patient may experience discomfort and a sense of swelling .
It should be noted that patients with difficulty staying still will be able to develop, after the procedure has begun, an annoying sense of discomfort .
Compared to the conventional CAT scan - which is completely painless - the contrast CT scan is slightly annoying due to the administration of the contrast medium.
How long does the CT scan with contrast?
If we consider the whole procedure (therefore, from when the patient changes to when the radiologist declares the scanning completed), the contrast CT scan lasts about 35 minutes .
If, however, only the part of the procedure dedicated to the creation of images is considered, the CT with contrast lasts a few minutes .
Did you know that ...
Thanks to advances in medical technology, today, the instruments that make any variant of the CT scan possible (contrast CT, angioTAC, CT without contrast, etc.) are much faster than those of a few decades ago.
On what occasions can the patient NOT go home immediately?
The reasons why a patient may have to postpone returning home after a CT scan with contrast are basically two:
- Because the exam provided unclear images . In this circumstance, the conditions exist for repeating the entire procedure.
- Because the patient feels slightly confused after the exam . This confusional state generally passes within a few minutes.
How to encourage the elimination of the contrast medium
To aid in eliminating the contrast medium used during the CT scan with contrast, radiologists suggest drinking plenty of water .
Compliance with this indication will allow the patient to eliminate the contrast agent administered within 24 hours.
risks
The TAC with contrast is reported for various risks, including:
- Non-negligible exposure to ionizing radiation . It is a fact that ionizing radiation is a factor favoring the development of malignancies, both malignant and benign.
Extent of risk: the dose of ionizing radiation emitted by the CT scan with contrast is equivalent to 2-4 years of natural radioactivity, depending on the anatomical district under examination. Comparing with a simple chest radiograph (RX-thorax), the latter exposes patients to a dose of ionizing radiation equal only to 10 days of natural radioactivity.
With this, we do not want to demonize the CT scan with contrast, but we just want to emphasize that its repetition is not recommended.
- Allergic reaction to contrast medium . It is a rare circumstance, which only affects predisposed patients. Almost always moderate and controllable with specific drugs, the most common symptoms of allergic reactions to the contrast medium are: hot flushes, nausea, strange tingling, hives and prolonged pain where there has been injection.
Contraindications
They represent a contraindication to the CT scan with contrast:
- The state of pregnancy ;
- A history of severe allergic reaction to an iodinated contrast agent;
- Obesity (CT scans with contrast can support people weighing no more than 150 kilograms);
- Renal insufficiency (this condition prevents the correct elimination of the contrast agent);
- Diabetes .
In some situations, it could become a contraindication to CT scans with even claustrophobia .
Is breastfeeding a contraindication to the use of the contrast medium?
Breastfeeding is not a contraindication to CT with contrast; however, most physicians and those who produce contrast media believe that breastfeeding is a practice to be avoided in the first 24-48 hours following the diagnostic examination.
Results
The results of the CT scan with contrast will be available to the patient only after the radiologist has analyzed the images generated during the examination.
As a rule, the wait for the results of the TAC with contrast is a few days .
Once the patient is in possession of the results, he will have to present them to his treating physician, so that he can consult them and make all the necessary decisions.
When is the Results available immediately?
If the CT scan with contrast represents an exam to be carried out urgently (for example, because the patient is in serious health conditions) the radiologist will analyze the images produced by the instrumentation at the time.
Advantages of TAC With Contrast
- Creation of images rich in details and of excellent quality, which allows to define very precise diagnoses;
- Minimal pain and minimal invasiveness;
- Thanks to its high detection capacity, it could make the use of exploratory surgery or biopsy superfluous;
- The images so rich in details that it provides are of enormous help during any subsequent surgical operations;
- Short term;
- Possibility of identifying different medical conditions;
- It is less sensitive to patient movements than nuclear magnetic resonance;
- Unlike nuclear magnetic resonance, it can be performed even if the patient has a metal prosthesis;
- It provides images in real time, so surgeons can take advantage of it just before an emergency surgery.
Those just listed are the main advantages of the CT with contrast.
