头部核磁共振

定义

A head MRI (magnetic resonance imaging) is an imaging test that uses powerful magnets and radio waves to create pictures of the brain and surrounding tissues.

它不使用辐射.

选择的名字

Nuclear magnetic resonance - cranial; Magnetic resonance imaging - cranial; MRI of the head; MRI - cranial; NMR - cranial; Cranial MRI; Brain MRI; MRI - brain; MRI - head

如何执行测试

头部核磁共振 is done in the hospital or a radiology center.

You lie on a narrow table, which slides into a large tunnel-shaped scanner.

Some MRI exams require a special dye, called contrast material. The dye is usually given during the test through a vein (IV) in your hand or forearm. The dye helps the radiologist see certain areas more clearly.

During the MRI, the person who operates the machine watches you from another room. The test most often lasts 30 to 60 minutes, but may take longer.

如何准备考试

You may be asked not to eat or drink anything for 4 to 6 hours before the scan.

Tell your health care provider if you are afraid of close spaces (have claustrophobia). You may receive medicine to help you feel sleepy and less anxious. Or your provider may suggest an "open" MRI, in which the machine is not as close to the body.

You may be asked to wear a hospital gown or clothing without metal ties (such as sweatpants and a t-shirt). 某些类型的金属会导致图像模糊.

在测试前，告诉你的十大赌博平台排行榜你是否有:

• 脑动脉瘤夹
• 人工心脏瓣膜
• 心脏除颤器或起搏器
• 内耳(耳蜗)植入物
• 肾脏疾病 or are on dialysis (you may not be able to receive contrast)
• 最近放置的人工关节
• 血管 支架
• Worked with sheet metal in the past (you may need tests to check for metal pieces in your eyes) 

核磁共振成像含有强磁铁. Metal objects are not allowed into the room with the MRI scanner. 这包括:

• 钢笔、小刀和眼镜
• Items such as jewelry, watches, credit cards, hearing aids
• Pins, hairpins, metal zippers, similar metallic items
• 可移动牙科手术

考试的感觉如何

If you need dye, you will feel the needle pinch in your arm when the dye is injected into the vein.

核磁共振检查不会引起疼痛. If you have difficulty lying still or are very nervous, you may be given a medicine to relax. Too much movement can blur the images and cause errors.

The table may be hard or cold, but you can ask for a blanket or pillow. The machine makes loud thumping and humming noises when turned on. 你可以要求戴上耳塞来减少噪音.

An intercom in the room allows you to speak to someone at any time. Some MRIs have televisions and special headphones that can help you pass the time or block the scanner noise.

There is no recovery time, unless you were given a medicine to relax. After an MRI scan, you can go back to your normal diet, activity, medicines.

为什么要进行测试

An MRI provides detailed pictures of the brain and nerve tissues.

A brain MRI can be used to diagnose and monitor many diseases and disorders that affect the brain, 包括:

• 出生缺陷
• 出血(蛛网膜下腔, subdural or epidural bleed or bleeding in the brain tissue itself)
• 动脉瘤
• 感染，比如 脑脓肿
• 肿瘤(癌性和非癌性)
• 荷尔蒙失调(如 肢端肥大症, 乳溢, 库欣综合症)
• 多发性硬化症
• 中风

An MRI scan of the head can also determine the cause of:

• 肌肉无力或麻木和刺痛
• 思想或行为的变化
• 听力损失
• Headaches when certain other symptoms or signs are present
• 说话困难
• 视力问题
• 痴呆

A special type of MRI called magnetic resonance angiography (MRA)可以用来观察大脑中的血管.

异常结果意味着什么

异常结果可能是由于:

• 脑部血管异常(头部动静脉畸形)
• Tumor of the nerve that connects the ear to the brain (听神经瘤)
• 颅内或周围出血
• 大脑感染
• 脑组织肿胀
• 脑部肿瘤
• 脑损伤:因受伤而对大脑造成的损伤
• 脑周围积液(脑积水)
• 颅骨感染(骨髓炎)
• 脑组织丢失
• 多发性硬化症
• 中风或短暂性脑缺血发作(蒂雅)
• 大脑的结构性问题

风险

核磁共振成像不使用辐射. To date, no side effects from the magnetic fields and radio waves have been reported.

The most common type of contrast (dye) used is gadolinium. 它很安全. 对这种物质的过敏反应很少发生. However, gadolinium can be harmful to people with kidney problems who are on dialysis. If you have kidney problems, tell your provider before the test.

The strong magnetic fields created during an MRI can make heart pacemakers and other implants not work as well. It can also cause a piece of metal inside your body to move or shift.

注意事项

MRI在怀孕期间是安全的. In many cases MRI may be more sensitive than CT scan to problems in the brain such as small masses. CT is usually better at looking for small areas of bleeding.

Tests that may be done instead of an MRI of the head include:

• 头部CT扫描
• 正电子发射断层扫描(宠物脑部扫描

在以下情况下，首选CT扫描, since it is faster and usually available right in the emergency room:

• 头部和面部的严重创伤
• Bleeding in the brain (within the first 24 to 48 hours)
• 中风的早期症状
• Skull bone disorders and disorders involving the bones of the ear

参考文献

Barras CD, Bhattacharya JJ. Current status of imaging of the brain and anatomical features. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. 格兰杰 & 艾利森诊断放射学. 7日艾德. Philadelphia, PA: Elsevier; 2021:chap 53.

陈国强，张国强. 磁共振成像(MRI) -诊断. 见:陈国强，张国强编. 实验室测试和诊断程序. 6日艾德. St Louis, MO: Elsevier Saunders; 2013:754-757.

张建军，张建军，张建军，张建军. 头颈部诊断影像概述. 见:Flint PW, Francis HW, Haughey BH，等编. 卡明斯耳鼻喉科:头颈外科. 7日艾德. Philadelphia, PA: Elsevier; 2021:chap 8.