Magnetic Resonance Imaging Examination (MRI)

1. Introduction

   Magnetic Resonance Imaging (MRI) is a safe, accurate, no radiation and painless imaging modality. It utilizes a strong magnetic field, radio waves, and state-of-the-art computer technology to produce excellent images and provide diagnostic information for suspected pathology in different parts of the human body.

2. Preparation

   • Unless otherwise specified in the appointment sheet, there are no food or drink restrictions.
   • Continue to take any medication prescribed by doctor unless otherwise directed.
   • Patients will be asked to change into a gown provided. Any loose ferromagnetic items, metallic objects (e.g. glasses, wrist watch, necklace, earrings, safety-pin, hair-slide, etc.), and items which may be damaged by the magnetic field (e.g. credit cards, Octopus card, HKID card, cell phones, etc.) should be removed prior to entering the magnet room. A locker will be provided for securing personal belongings.
   • Eye make-up should be avoided on the day of examination.
   • Inform staff if the patient has the following items or conditions because they are potentially hazardous and may interfere with the MRI examination by producing artefacts:
     • Cardiac implantable electronic devices such as cardiac pacemaker or implantable cardioverter defibrillator (ICD), prosthetic heart valve, cardiac occluders or closure devices.
     • Metallic foreign bodies.
     • Being or used to be a metal worker.
     • Injured by metallic fragment, shrapnel, bullet or any metallic foreign body.
     • Having tattoo or permanent eye-lining.
     • Having history of renal failure, renal disease or renal surgery.
     • Being pregnant or suspecting pregnancy
     • Suffering from claustrophobia.

3. Procedure

   • MRI examinations may take between 30 minutes to 1 hour to complete depending on the body part to be imaged. Patients are required to keep still during the examination. Some patients may require sedation or even general anaesthesia in order to prevent movements during the examination.
   • Ear plugs or headphone will be provided to protect patients from the noise generated by the machine during the examination.
   • An intercom system is installed inside the examination room so that patients can communicate with staff during the examination to enhance safety. In addition, an emergency call bell is also available for patients to seek assistance if necessary.
   • In some examinations, Gadolinium-based MR contrast agent will be administered intravenously in order to show the pathology more clearly.

4. After the examination

   Normally the examination will not cause any discomfort. After the scan, normal activities could be resumed without any restrictions. The MRI images will be examined by radiologist and the MRI report will be sent to the referring clinician.

5. Complications

   Long term biological effects of MRI examination on human body and fetus are still not fully established.

   General risks include:

   • Noise is unavoidable during the course of the MRI examination. There might be a loud tapping, knocking or chirping sound during the examination. The sound loudness can be up to 130dB or above. Peripheral nerve stimulation may be caused with transient tingling sensation, muscle twitching, warmth and pain.
   • Claustrophobia: anxiety response, excessive fear or panic attack when exposure to enclose MRI gantry.
   • Gadolinium-based MR contrast media is a very safe drug. Reactions are uncommon and usually very mild. Minor reactions such as headache, dizziness, nausea or vomiting, might occur in about 1% of patients. Contrast medium extravasation can cause some discomfort, swelling or pain at the injection site that usually disappears in one or two days.

   Specific risks or complications (including low probability serious consequence risks or complications) include:

   • Under rare circumstances, Gadolinium-based MR contrast media can cause severe reaction such as convulsion, severe anaphylaxis and death. The chance of this fatal occurrence is about 1 in 400,000.
   • Implants or devices that are non-compatible with MRI might be displaced, heated up and causing tissue burning, malfunction or attached to the magnet.
   • Patients with renal failure may have a probability of 1-7% in developing nephrogenic systemic fibrosis after receiving intravenous Gadolinium-based MR contrast media. Some affected patients can develop joint contractures, joint immobility, multi-organ failure. This reaction may in very rare cases be fatal.

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.