眼眶CT扫描

定义

A computed tomography (CT) scan of the orbit is an imaging method. It uses x-rays to create detailed pictures of the eye sockets (orbits), eyes and surrounding bones.

选择的名字

CT scan - orbital; Eye CT scan; Computed tomography scan - orbit

如何执行测试

You will be asked to lie on a narrow table that slides into the center of the CT scanner. Only your head is placed inside the CT scanner.

You may lie on your back, or you may lie face-down with your chin raised. You may be allowed to rest your head on a pillow.

一旦你进入扫描仪, 机器的x射线束绕着你旋转, 但是你不会看到x光片.

A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. The computer can create three-dimensional models of the body area by stacking the slices together.

You must lie still during the exam, because movement causes blurred images. You may be asked to hold your breath for short periods. You may be asked to remove jewelry and earrings.

实际扫描大约需要30秒. 整个过程大约需要15分钟.

如何准备考试

考试前:

• You will be asked to remove jewelry and wear a hospital gown during the study.
• If you weigh more than 300 pounds (135 kilograms), find out if the CT machine has a weight limit. Too much weight can cause damage to the scanner's working parts.

某些检查需要一种特殊的染料, 叫对比, to be delivered into the body before the test starts. Contrast helps certain areas show up better on the x-rays. Contrast can be given through a vein (intravenous - IV) in your hand or forearm.

Before the scan using contrast, it is important to know the following:

• You may be asked not to eat or drink anything for 4 to 6 hours before the test.
• Let your health care provider know if you have ever had a reaction to contrast. You may need to take medicines before the test in order to safely receive this substance.
• Tell your provider if you take the diabetes medicine metformin (Glucophage). 你可能需要采取额外的预防措施.
• Let your provider know if you have poor kidney function. This is because the contrast can worsen the kidney function.

考试的感觉如何

Some people may have discomfort from lying on the hard table.

Contrast given through an IV may cause a slight burning sensation. You may also have a metallic taste in the mouth and a warm flushing of the body. These sensations are normal and most often go away within a few seconds.

为什么要进行测试

This test is helpful for diagnosing diseases that affect the following areas around the eyes:

• 血管
• 眼部肌肉
• 支配眼睛的神经(视神经)
• 鼻窦

An orbit CT scan may also be used to detect:

• 眼部脓肿(感染)
• 眶骨骨折
• 眼窝内有异物

异常结果意味着什么

异常结果可能意味着:

• 出血
• 眶骨骨折
• 格雷夫斯病
• 感染
• 肿瘤

风险

CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. The risk associated with any individual scan is very low. 随着扫描次数的增加，风险也在增加.

CT scans are done when the benefits greatly outweigh the risks. 例如, 不做检查的风险更大, especially if your provider thinks you might have cancer or a fracture.

The most common type of contrast given into a vein contains iodine.

• If a person with an iodine allergy is given this type of contrast, 恶心想吐, 打喷嚏, 呕吐, 瘙痒, 或者可能出现荨麻疹.
• If you have a known allergy to contrast but need it for a successful exam, you may receive antihistamines (such as Benadryl) or steroids before the test.

The kidneys help filter the iodine out of the body. 如果你有肾脏疾病或糖尿病, you should be closely monitored for kidney problems after contrast is given. 如果你有糖尿病或肾脏疾病, talk to your provider before the test to know your risks.

在接受对比之前, tell your provider if you take the diabetes medicine metformin (Glucophage) because you may need to take extra precautions. You may need to stop the medicine for 48 hours after the test.

In rare cases, the dye can cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, tell the scanner operator right away. Scanners come with an intercom and speakers, so the operator can hear you at all times.

参考文献

康佩恩T, Miszkiel K, Davagnanam I. 轨道. 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 60.

Guluma K, Lee JE. 眼科学. In: Walls RM，编辑. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10日艾德. Philadelphia, PA: Elsevier; 2023:chap 57.

Poon CS, abraham M, abraham JJ. 轨道. 见:Haaga JR, Boll DT编. 全身CT和MRI. 6日艾德. Philadelphia, PA: Elsevier; 2017:chap 20.

鲑鱼摩根富林明. 轨道. 在:鲑鱼JF, ed. 坎斯基临床眼科学. 9日艾德. Philadelphia, PA: Elsevier; 2020:chap 4.