FAQ – frequently asked questions about CT and MRI scans

The administration of a contrast agent requires the insertion of a venflon before the examination begins. The sensations accompanying the injection (insertion) are very subjective. Most patients assess them as discomfort, similar to that during blood draws.

The administration of the contrast agent itself is already taking place during the examination and may cause a warm/cold or slight spreading sensation at the site of administration, as well as a feeling of pushing on the bladder or the appearance of a metallic aftertaste in the mouth. The sensations described above subside after a few or tens of seconds. However, they should not be feared, as they are a natural reaction of the body to the shading agent.

After contrast administration, most people do not experience any pain. However, there is a small group of patients, allergic or intolerant to certain components of contrast agents, who may experience discomfort or, in extreme cases, a sensation of acute pain at the injection site. It should be emphasized, however, that these are individual situations.

As with the administration of almost any medical substance into the body, there is a small risk that the patient may develop an allergic reaction. We are unable to rule this out before the examination. If the patient has had any worrisome symptoms during previous imaging studies, he or she should notify the nurse or electrocardiologist before the study begins.

For computed tomography (CT) scans:

• • Allergy to: iodine (iohexol);
  • Hyperthyroidism (reduced TSH levels);
  • Renal failure (elevated creatinine, reduced eGFR);

For magnetic resonance (MR):

• • Allergy to the following substances: gadoteric acid, meglumine, tetraxetan (DOTA)
  • Renal failure (elevated creatinine, reduced eGFR);

Sometimes patients with elevated creatinine levels are tested – this is decided on a case-by-case basis.

The administration of the contrast agent is associated with a small risk of an allergic reaction in the patient, to any of the components of the drug.

In addition, there is a negligible risk of contrast extravasation during the administration of a contrast agent, i.e. the contrast agent will not flow with the venous vessels to the heart, but will “get stuck” between the tissues in the area of the intravenous cannula (venflon) insertion. Unfortunately, such a situation can happen, despite the utmost care and attention of medical personnel. In the situation of its occurrence, our Team is prepared to take care of the patient and minimize the risk of side effects of extravasation. At the same time, the patient will be fully instructed on how to care for the area where the contrast has collected.

Although contrast agents should not have a negative effect on our body, it is very rare that their use has side effects. They can be divided into three different levels:

• mild – nausea, mild vomiting, hives, pruritus, erythema, sensation of warmth, restlessness, spontaneously resolving vasovagal reaction (i.e. vasodilation of blood vessels and slowing of heart rate) and others
• Moderate – bronchospasm, facial/laryngeal edema, vasovagal reaction and others
• serious – hypotensive shock, respiratory arrest, arrhythmia, cardiac arrest and others

For exact information on possible side effects, we refer to the leaflet that comes with the contrast agent – we will make the name of the preparation and the leaflet available at the laboratory upon patient request.

Yes. Contrast agent for some procedures is necessary for the doctor to make a reliable description of the examination performed. The substance, true to its name, increases contrast between different tissues, making it easier for the radiologist to distinguish normal tissues and areas from those that are lesioned.

Note: There are examinations that do not require the administration of contrast. If you have doubts about whether a contrast agent should be administered in the examination you plan to perform, we will be happy to dispel your doubts on our hotline.

We recommend that patients abstain from food 5-6h before the start of the study with contrast agent administration.

If the patient has any doubt about negative reactions of the contrast agent with the medications he or she is taking, he or she should see the attending physician and determine whether the contrast can be administered. The attending physician has full records of the patient’s medical history and is able to assess whether the medications the patient is taking on a regular basis might have any negative reaction with the contrast agent.

Some imaging studies can be performed without the administration of a contrast agent. However, there are also a number of examinations during which the administration of contrast is necessary to achieve maximum imaging value. This is extremely important for obtaining a reliable diagnosis, since sometimes only the application of a contrast agent allows visualization of lesional areas. It is worth noting that the substances used as shadowing agents are internationally recognized and used drugs, and a potential disease that is not fully diagnosed can have much more negative consequences for the patient’s health than performing an examination with contrast.

No, the contrast administered in CT and MRI scans does not exhibit radioactivity.

Administration of contrast each time results in prolongation of the examination. Depending on the area examined, the prolongation ranges from several to several minutes, compared to the examination without the use of a shadowing agent.

According to the recommendations, alcohol should not be consumed 24 hours before and 24 hours after the test. This is because alcohol can lead to dehydration, which can consequently have a detrimental effect on the functioning of the kidneys and their excretion of contrast.

It is not recommended to drive or operate machinery for a minimum of 1h after administration of the contrast agent. This is due to the possibility of dizziness and nausea. If you feel unwell after the test, you should not drive or operate machinery until your symptoms subside.