CT FAQ

A: According to the examination requested by the doctor and the clinical indication, some patients will be given an intravenous injection of contrast medium to better define the blood vessels and to accentuate the appearance between different tissues e.g. abdominal aortogram, liver cancer and lung cancer.

A: Iodinated contrast media are commonly used in radiological investigations. They are generally safe although adverse reactions are occasionally encountered.

A) Acute Adverse Reaction

Acute adverse events can be categorised as either allergic-like or physiologic. Allergic-like reactions often occur immediately or within 20 minutes after contrast injection. The severity of acute adverse reaction can be defined as mild, moderate and severe.

1. Mild reactions
   Mild reactions are self-limited and usually no medical management is required, such as limited urticaria, itchiness, erythema, nausea, mild vomiting, sneezing, coughing, warmth, chills, rhinorrhea, etc.

2. Moderate reactions*
   Reactions namely marked urticaria, mild bronchospasm, facial edema, laryngeal edema, shortness of breath, wheezing.

3. Severe reactions*
   They are often life-threatening, such as hypotensive shock, respiratory arrest, cardiac arrest, arrhythmia, convulsion, death.

* Acute moderate or severe adverse reactions usually require medical treatment. A mild reaction may develop into a more serious reaction and can even cause serious harm. Nevertheless, our staff are professionally trained and well equipped to recognise and manage the contrast adverse reactions properly. Patient will be asked to rest in a medical environment for at least 20 minutes after contrast agent injection.

Please inform referring doctor and our staff before examination if the patient has previous history of allergy to iodinated contrast medium. Steroid premedication may be advised before the scan.

B) Delayed Adverse Reaction

Delayed adverse reactions may occur from one hour to up to one week following contrast medium injection. These are commonly skin reactions and include urticaria, rash and itchiness. Rare delayed reactions include iodide “mumps” and acute joint pain. Most of the late reactions are skin reactions which include maculopapular rash, angioedema, urticaria and erythema. (Skin reactions are often mild to moderate and self-limited.)

C) Other

Contrast extravasation – Extravasation of contrast media is a potential complication that has an overall incidence of less than 1% and is due to leakage of contrast media to soft tissue adjacent to the injection site. Extravasation of small amount of contrast media may result in swelling and/or pain, and is commonly self-limited. More severe injuries may result in skin ulceration, tissue necrosis and compartment syndromes. It is important to let our staff know immediately if there is unusual discomfort or pain at the injection site during or after contrast injection.

A: Radiation exposure in a CT examination is minimal for adults and should produce no effects, but NOT for fetus in pregnant women. Tell your doctor and our staff if you think you are pregnant or may be pregnant as the CT scanner uses x-rays which might cause radiation hazard to fetus.

A: Breast-feeding after the injection of iodinated contrast medium is safe as only 0.5% of the maternal dose is excreted into breast milk. Concerned mothers may discard breast milk for 24 hours after injection to eliminate fetal exposure to contrast medium.

A: Yes, a requisition form signed by your doctor will provide us with your necessary clinical information; and we will tailor the examination accordingly.

A: The more information that our radiologist has when he reviews your study, the more specific the interpretation will be. Correlations with other studies are often helpful.

A: After completion of the CT scan, radiologist will interpret the CT scan and issue an imaging report to the referring doctor who will then explain the findings and diagnosis.