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MRI imaging is a safe, radiation free and non-harmful form of imaging with a broad range of applications. Through the use of strong magnets, electromagnetic waves and specialised computer technology, the medical professional can gain an incredibly accurate image of the body’s internal organs and tissues, enabling a much more accurate diagnosis on each individual patient case. With the most up to date large bore MRI in use, any possibility of side-effects and the discomfort from the time taken to complete the examination have all been reduced to a minimum.


The following is information on the side effects from an MRI, a comparison of the various types of medical scanning procedures, and the latest MRI technology offered by this clinic.

MRI Uses

MRI gives clearer and more detailed images of soft tissue areas of the body than any other imaging method and therefore is frequently used to assess areas such as the brain, spine, joints, heart, abdomen and blood vessels. Taking cancer as an example, an MRI can help detect the location and stage of the tumour and monitor the changes of the tumour before and after treatment, such as detecting the signs of metastasis or spreading. The doctor will decide whether the patient is suited to an MRI scan. In general, an MRI scan takes approximately 30 minutes.


Due to the strong magnets used during the scan, patients must remove any metal from their bodies before getting scanned to avoid accidents. Patients with certain metal implants or fragments such as a cardiac pacemaker, metal spine device, aneurysm clips or hearing aid implants are strongly advised against undergoing the MRI examination. However, patients with dentures should be fine to proceed with an MRI scan.

What are the side effects of MRI?

Because MRI does not involve any ionizing radiation, there will be no risk of exposure to radiation during an MRI scan. In general, discomfort does not occur after getting an MRI assessment, although in some cases people might develop allergic reactions to the contrast dye used in the MRI procedure.

  • MRI side effects | Allergic reactions to MRI contrast dye

Contrast dye is injected into a blood vessel and in general, it is very safe, though not every patient will need a contrast dye injection. Some people may develop allergic reactions to the contrast dye. About 1% of patients receiving an MRI scan may experience mild side effects such as itchy skin, nausea, pain in the injected area, or feeling cold or hot.


For more severe side effects, patients might experience bronchospasm and severely low blood pressure. Patients with severe kidney failure or who undertake haemodialysis may develop nephrogenic systemic fibrosis (NSF) as a result of the allergic reaction to the contrast dye. Severe reactions can be fatal, although it would be extremely rare.

  • MRI side effects | Pregnancy

So far it remains unknown how MRI affects patients during pregnancy. In general, patients less than 12 weeks pregnant are not advised to get an MRI scan, while breastfeeding mothers will not be affected by the MRI contrast dye. If a contrast dye injection is required for the scan, we advise that patients who are breastfeeding should prepare 2 days of milk in advance before the MRI scan. They can continue breastfeeding when the contrast dye has been secreted from their system through urine, which usually takes about 24 hours.

  • MRI side effects | Anxiety

Conventional MRI machine might create noise which sometimes reaches to a high rate of 100 Hz/s, equivalent to the noises generated from a drill machine and high-speed train. The harsh and strong sound can create unease and anxiety in patients. In addition, children or patients with claustrophobia may feel scared and experience a choking sensation after entering the scanner. If this is the case, the attending doctor or radiologist will provide appropriate assistance, including allowing family members to keep the patients company during the assessment, and arranging a tour of the room and scanner for them before the actual scan takes place. In some cases, patients may be given a small dose of sedative so that they can proceed with and complete the MRI scan in a more relaxed state.

Are there any diagnostic methods that can replace MRI?

MRI is not the only imaging technique available for cancer scanning. There are various imaging procedures with different benefits and uses. Patients should consult their doctor and pick the scanning method that fits their actual diagnostic needs.


Benefits:Generates detailed images of internal body structures

Cancer Treatment:Breast cancer screening and diagnosis, including 3D mammography.

Level of Radiation:Minimal level of radiation


Benefits:Detect the real-time changes in organs but with a decreased sensitivity for tissues like bones and a lower imaging resolution.

Cancer Treatment:Cancer scanning such as prostate ultrasound and bladder ultrasound.
Level of Radiation:No ionizing radiation

Computer Tomography (CT)

Benefits:Captures the details of internal structures from many angles and produces two-dimensional and three-dimensional images.

Cancer Treatment:Applied to various cancer diagnoses

Level of Radiation:A higher level of radiation that X-Ray but there is a low-dose CT scan
For more information

Positron Emission Tomography/Computed Tomography(PET-CT)

Benefits:Generates three-dimensional coloured images with accuracy further improved by CT and data.

Cancer Treatment:Applied to early-stage cancer detection, malignant tumour detection, cancer staging, tumour localization, treatment monitoring.

Level of Radiation:The latest AsiR low-radiation technology can reduce 50% of radiation doses than conventional PET-CT scan.
For more information

Magnetic Resonance Imaging(MRI)

Benefits:Produces detailed images of the soft-tissue masses and nerves.

Cancer Treatment:Detects the location and changes in the tumour.

Level of Radiation:No ionizing radiation

HKIOC Services

HKIOC provides a wide range of services for medical assessment including imaging scanning and interventional radiological services. They are:




  1. U.S. FDA: MRI, Benefits and Risks https://www.fda.gov/radiation-emitting-products/mri-magnetic-resonance-imaging/benefits-and-risks