The role of MRI contrast agents

Magnetic resonance imaging (MRI) is a common medical imaging technique widely used in the diagnosis of various diseases, including tumors, neurological disorders, and cardiovascular diseases. To improve image clarity and contrast, doctors often use contrast agents (contrast agents) to enhance the viewing of specific tissues and organs. Contrast dyes can help doctors more accurately locate lesions and develop more effective treatment plans. In Hong Kong, many medical institutions such as "Hong Kong Examination" provide professional MRI services, but "?" Many people may ask. In addition to considering advanced equipment, it is also necessary to understand the potential risks and side effects of contrast media when choosing the right healthcare provider.

Types of MRI contrast agents

Gadolinium contrast agents (gadolinium-based contrast agents, GBCAs)

Gadolinium contrast agent is currently the most commonly used MRI contrast agent, and its core component is the metallic element gadolinium. Gadolinium is highly magnetic and can significantly improve image contrast. Depending on the different chemical structures, GBCA is linearly cyclic

• Linear gadolinium contrast agent.:如 Gadodiamide、Gadopentetate,其結構較不穩定,釓離子容易游離,可能増加副作用風險。
• Large cyclic gadolinium contrast agent.: Such as gadobutrol and gadoterate, which are quite stable and safe.

According to the Hong Kong Health Bureau, about 80% of MRI examinations use gadolinium contrast agent, but in recent years, the proportion of large ring contrast agents has gradually increased due to safety concerns.

Other types of contrast media

Besides gadolinium contrast agents, there are other types of contrast media, such as superparamagnetic iron oxide (SPIO) and manganese-containing contrast agents, which have less clinical application and are mainly used in specific studies or special cases.

Common side effects of MRI contrast agents

anaphylaxis

Contrast agents can cause allergic reactions ranging from mild to severe.

• Mild reactions: rash, itching, nausea, etc., the incidence is about 1-2%.
• Severe reactions.: Difficulty breathing, a sudden drop in blood pressure, shock, etc., the incidence is less than 0.1%, but it should be treated immediately.

In case of an allergic reaction, your healthcare provider will give you an antihistamine or epinephrine depending on the situation. For patients with a history of allergies, it is recommended to inform their doctor before the examination and consider using hypoallergenic contrast agents.

Kidney Effects: Nephrogenic Systemic Fibrosis (NSF)

NSF is a rare but serious complication associated with the accumulation of gadolinium contrast agents, especially in patients with renal failure. Risk factors include:

• Chronic kidney disease (GFR
• Acute kidney injury
• Multiple use of high-dose gadolinium contrast agent

The key to preventing NSF is to assess kidney function before testing and choose a large cyclic gadolinium contrast agent. Some medical institutions in Hong Kong, such as the Examination Association, require patients to submit a recent kidney function report to ensure safety.

Other rare side effects

In rare cases, the developer can cause headaches, dizziness, or a metallic taste, but these are usually short-lived and do not require special treatment.

Strategies to Reduce the Risk of Contrast Side Effects

Pre-test assessment

Renal function assessments (e.g., measurement of serum creatinine and estimated GFR) should be performed prior to testing and a detailed allergy history should be asked. For high-risk patients, your doctor may adjust the type or dose of contrast dye.香港駿檢好唔好

Use the lowest effective dose

Based on the patient's weight and the test site, the doctor calculates the lowest effective dose to reduce unnecessary exposure.

Choose a safer contrast agent

Macrocyclic gadolinium contrast agent is highly stable and is the first choice for patients with reduced renal function. Some high-end medical centers in Hong Kong have fully adopted this type of contrast agent.

hydration

Proper hydration (e.g., intravenous fluids or oral hydration) before and after the test can speed up the excretion of contrast media and reduce the burden on the kidneys.

Guidelines for the risks and safe use of MRI contrast agents

While MRI contrast agents can improve diagnostic accuracy, potential side effects cannot be ignored. When selecting "Hong Kong Inspection", preference should be given to institutions with advanced equipment and medical expertise, such as "Hong Kong Inspection". Before the test, it is important to communicate well with your doctor, understand your own risks, and take corresponding precautions to ensure the safety and effectiveness of the test.

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