Hong Kong Imaging and Diagnostic Centre

Cardiac Computed Tomography (Cardiac CT) Scan

What is a Cardiac CT Scan?

Cardiac computed tomography, or cardiac CT, is a painless test that uses an x-ray machine to take clear, detailed pictures of the heart.

A cardiac CT is mainly used to detect:
  • whether the coronary arteries are narrow or blocked,
  • if there is calcium buildup in the walls of the coronary arteries,
  • if there are problems with heart function or heart valves,
  • the cause of chest pain or unclear ECG or abnormal blood test results,
  • signs of pericardial disease, that occurs in the sac around the heart,
  • if there are problems with the aorta, the main artery that carries blood from the heart to the body, and, in particular, if there are potentially life-threatening aneurysms or pulmonary embolism (blood clots in the lungs).

How is a Cardiac CT done?

During a cardiac CT scan, an x-ray machine will move around your body in a circle. The machine will take a picture of each part of your heart and a computer will put the pictures together to make a three-dimensional (3D) picture of the whole heart.

Cardiac CT involves radiation. At Hong Kong Imaging, our new CT scanner is an Ultra-Low Dose CT that employs the latest CT technology that reduces the patient dose to about 1/6 of that of a standard CT, with optimization of image quality and reduction in metallic artifacts.

What to expect

The technician may place small electrodes (sticky discs) onto your chest. These are attached to an electrocardiograph (ECG) monitor, which shows your heart's electrical activity during the test.

Before the examination, you may be given medicine to help slow your heart rate. You will be asked to remain motionless for the length of the examination. Some studies will require you to hold your breath. The technician will be in the room and help instruct you.


Some CT scans require Intravenous (IV) injection of contrast medium into a vein, usually administered into the back of the hand. You may notice a hot flush feeling, and experience an unusual metallic taste or smell after the IV injection. These sensations are normal and usually only last between 10 and 60 seconds. This dye highlights your coronary (heart) arteries on the x-ray pictures. This type of CT scan is called a coronary CT angiography, or CTA.

What to expect afterwards

Your radiologist will examine your scans and send the film and report to your referring doctor.

After your procedure you will be able to resume all normal activities. If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your physician straight away.

If you have been given a sedative, please ask a relative or friend to collect you from the examination and do not drive or operate machinery.

What You Must Tell Us

  • Please tell the technician if you are pregnant, or suspect you might be pregnant, or are breast-feeding.
  • If you have had an adverse reaction to a previous contrast injection or any other drugs.
  • Please inform our staff if you have any allergies, recent illness, a history of asthma, heart disease, renal impairment, thyroid problems, or diabetes mellitus
  • If you are diabetic, you should not take insulin or anti-diabetic drug before the examination. Please let the technician know if you take any diabetic medication that contains metformin - examples are diabex, diaformin, avandament, glucomet, novamet, genex, glucophage, insulin, or blood thinner (warfarin or aspirin products).
  • Please inform the technician if you have taken any diet pills, Viagra or similar medication within 24 hours.

How to Prepare

You will be shown to a private changing area and will be given a gown to change into. You will be asked to remove jewellery, eyeglasses, underwired brassieres, piercings and metal objects that could interfere with the x-ray images.

Contrast Examination
  • Fast for 4 hours prior to the scheduled examination. Plain water is allowed.
  • Do not drink coffee, tea or soft drinks on the date of examination. Do not take diet pills, Viagra or similar medication for 24 hours before the examination.
  • Do not take diabetes mellitus medication , e.g. Metformin 24 hours prior to examination. Resume intake of DM medication 48 hours after the examination.
  • Oral contrast (provided by our centre) may be required for certain examination.
  • Please inform our staff if there are any allergy history.
  • Please bring any previous CT films and results on the examination date in case they are needed for comparison.