膝关节CT扫描

定义

A computed tomography (CT) scan of the knee is a test that uses x-rays to take detailed images of the knee.

选择的名字

CAT scan - knee; Computed axial tomography scan - knee; Computed tomography scan - knee

如何执行测试

You will lie on a narrow table that slides into the center of the CT scanner.

When you are inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam without stopping.)

A computer makes several images of the body area. 这些被称为切片. These images can be stored, viewed on a monitor, or printed on film. Models of the body area in 3-D can be created by adding the slices together.

You must stay still during the exam, because movement blurs the pictures. 你可能有 to hold your breath for short periods of time.

The scan should take less than 20 minutes.

如何准备考试

Some exams require a special dye, called contrast, to be injected into your body before the test. Contrast helps certain areas show up better on the x-rays.

• Contrast can be given through a vein (IV). 如果使用对比, you may also 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 to avoid this problem.
• 在接受对比之前, tell your provider if you take the diabetes medicine metformin (Glucophage). You may need to take extra steps if you are taking this medicine.

Too much weight can cause damage to the scanner's working parts. Ask about the weight limit before the test if you weigh more than 300 pounds (135 kilograms).

You will need to remove jewelry and wear a hospital gown during the CT exam as metal can affect the CT images.

考试的感觉如何

Some people may be uncomfortable lying on the hard table.

静脉注射造影剂可能导致:

• 轻微的灼烧感
• 口中有金属味
• 身体温热潮红

These feelings are normal and usually go away within a few seconds.

为什么要进行测试

A CT scan can quickly create more detailed pictures of the knee than standard x-rays. 该测试可用于检测:

• 脓肿 或感染
• 骨折
• Examine fractures and pattern of fractures
• The cause of pain or other problems in the knee joint (usually when 核磁共振成像 做不到)
• 肿块和肿瘤，包括癌症
• Healing problems or scar tissue following injuries or surgery

A CT scan may also be used to guide a surgeon to the right area during a 活组织检查.

正常的结果

Results are considered normal if no problems are seen.

异常结果意味着什么

异常结果可能是由于:

• 脓肿(脓液聚集)
• 关节炎
• 骨折
• 骨肿瘤或癌症
• Healing problems or scar tissue after surgery

风险

CT扫描的风险包括:

• 暴露于辐射
• 对比染料过敏
• 如果在怀孕期间造成先天缺陷

CT scans give off more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your provider should discuss this risk compared with the value of an accurate diagnosis for the problem.

Let your provider know if you have ever had an allergic reaction to injected contrast dye.

• The most common type of contrast contains iodine. 你可能有 恶心或呕吐, 打喷嚏, 瘙痒, or 荨麻疹 如果你对碘过敏.
• If you need to have this kind of contrast, you may need antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. You may need extra fluids after the test to help rid your body of the iodine if you have kidney disease or diabetes.

Rarely, the dye may cause a serious allergic response called 速发型过敏反应. 这可能会危及生命. Notify the scanner operator right away if you have any trouble breathing during the test. Scanners have an intercom and speakers so the operator can hear you at all times.

参考文献

达马塞纳一世，斯伯丁一世. Computed tomography of the knee joint: indications and significance. 见:LaPrade RF, Chahla J编. Evidence-based Management of Complex Knee Injuries. St Louis, MO: Elsevier; 2021:chap 4.

Kapoor G, tom AP. Current status of imaging of the musculoskeletal system. 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 38.

Madoff SD, Burak JS, Math KR, Walz DM. Knee imaging techniques and normal anatomy. 编辑:Scott WN, ed. Insall & 斯科特膝盖手术. 6日艾德. Philadelphia, PA: Elsevier; 2018:chap 5.

少校N，科尔曼C. 膝关节影像学. 见:米勒博士，汤普森博士，编辑. 口腔、Drez & 米勒的骨科运动医学. 5日艾德. Philadelphia, PA: Elsevier; 2020:chap 91.