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Computed Tomography (CT)

  1. Introduction

    Computed Tomography (CT) makes use of computer technology together with a rotating x-ray device to create detailed cross-sectional images of the organs or areas of the body to provide diagnostic information for suspected pathology.

  2. Preparation

    • Inform doctor of history of allergy to food and drugs, particularly any previous reaction to contrast medium, asthma, urticaria, eczema, allergic rhinitis, etc.
    • Inform staff before the examination if you are or may be pregnant.
    • Diabetic patients should consult clinician concerned for the adjustment of drug dosage.
    • Fasting is needed for 4 hours prior to the examination.
    • Take oral contrast medium or water some hours before an abdominal CT scan.
    • In-patients could take oral contrast medium or water in the ward.
    • If intravenous injection of contrast medium is indicated, a written consent is required.
  3. Procedure

    • The patient will be lying on the table of the CT scanner. The table will then carry the patient slowly through the gantry of the scanner and a well-collimated X-Ray beam will pass through the patient. A number of cross-sectional images of the organs/areas will be made.
    • During CT scanning, the patient should stay still and listen carefully to instructions given by staff.
    • The whole procedure is monitored by a radiologist. Intravenous or oral contrast medium may be needed to improve the diagnostic quality of the images. A written consent will then be required.
    • For paediatric patients, in order to obtain images without undue movement, medication for sedation are sometime administered.
    • Time for examination may vary depending on individual circumstances and usually takes half a day.
  4. After the examination

    Patients can eat or drink as usual after the examination. The report of the scan will be sent to doctor concerned.

  5. Complications

    • In general, contrast medium is a safe drug. However, side effects may occasionally occur.
    • General risks include:
      • Mild reactions: Feeling of warmth, itching, nausea, vomiting, arm pain, sneezing, coughing, and chest tightness. A few patients may experience delayed reactions, which are usually occurred within 24 hours, including pain at injection path, itching, rash, painful or swollen salivary glands. The symptoms are usually transient, requiring minimal or no treatment.
      • Moderate reactions: These are more severe and last for a longer duration. Patients may also experience rash or urticaria, fever and chills, an increase or decrease in blood pressure and palpitation. Specific treatment and close monitoring are required.
      • Severe reactions: Shortness of breath irregular heartbeat, chest pain, severe kidney failure, convulsion and unconsciousness. If these symptoms occur, urgent medical treatment is needed.
    • Specific risks:
      • Contrast extravasation may occur during intravenous contrast injection. The patient will feel discomfort or pain at the injection site. In extremely rare situation, the contrast medium may cause death due to severe allergic reactions.
  6. Project on enhancing radiological investigation services through collaboration with the private sector (radi collaboration)

    As a crucial tool of patient assessment, the demand for radiological imaging services in the Hospital Authority (HA) has been rising rapidly. Radi Collaboration (the Project) is a government-funded project aiming at enhancing radiological investigation services for patients through collaboration with the private sector.

    The target patients of the Project are HA’s cancer patients. Patients fulfilling specific clinical criteria can be referred to the private sector for radiological diagnostic examinations as part of their cancer care.

    The Project provides Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) services to patients. Target patients having clinical need to receive such investigation(s) can be invited to take part in the Project on a voluntary basis under full subsidy. HA will continue to provide service to those who choose to receive service from the public sector.

    Patients accepting HA’s invitation can choose their participating service providers (PSPs) out of HA’s list and HA will make referral according to their choice. Results of investigations will be returned to HA Hospitals through an electronic platform for clinicians to formulate subsequent treatment plan. Generally speaking, PSPs will provide service to patients within 5 working days. HA doctors will invite patients to take part in the project during consultation and on-site enrollment will be arranged for patients accepting the offer. There is no need for patients to apply themselves.

    Please visit the Hospital Authority's website for details.

  7. Remarks

    Should you have any queries, please consult doctor-in-charge.