What is a CT scan?

Computed tomography is commonly referred to as a CT scan. A CT scan is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce images of the inside of the body. It shows detailed images of any part of the body, including the bones, muscles, fat, organs and blood vessels.

CT scans are more detailed than standard X-rays. In standard X-rays, a beam of energy is aimed at the body part being studied. 身体部位后面的一个板捕捉能量束穿过皮肤后的变化, bone, muscle and other tissue. While much information can be obtained from a regular X-ray, a lot of detail about internal organs and other structures is not available.

In CT, the X-ray beam moves in a circle around the body. 这允许对同一器官或结构有许多不同的看法，并提供更多的细节. x射线信息被发送到一台计算机，该计算机解释x射线数据并在显示器上以二维形式显示. Newer technology and computer software makes three-dimensional images possible.

CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage. CT can also be used for a tissue or fluid biopsy.

Why are CT scans sometimes ordered with contrast?

CT scans may be done with or without contrast. 造影剂是指口服或静脉注射的物质，使所研究的特定器官或组织被看得更清楚. 对比检查可能要求你在检查前禁食一段时间. Your doctor will notify you of this prior to the procedure.

你需要让你的医生知道你是否对任何造影剂有反应和/或任何肾脏问题. 报告的海鲜过敏不被认为是碘造影剂的禁忌症. If you have any medical conditions or recent illnesses, inform your doctor.

How do I prepare for a CT scan?

If you are having a computed tomography angiography (CTA) or a virtual colonoscopy, you will be given specific instructions when you make your appointment.

PRECAUTIONS: If you are pregnant or think you may be pregnant, please check with your doctor before scheduling the exam.

CLOTHING: You may be asked to change into a patient gown. If so, a gown will be provided for you. Please remove all piercings and leave all jewelry and valuables at home.

CONTRAST MEDIA: Contrast may be indicated for your exam. 造影剂提高了放射科医生发现异常结构和更好地了解正常解剖结构的能力.

• Some patients should not have an iodine-based contrast media. 如果您的肾功能有问题，请提前告知您的放射科医生. 我们也许可以在不使用造影剂的情况下进行扫描，或者找到替代的成像检查.
• The most common type of CT scan with contrast is the double-contrast study, 除了静脉造影剂，你还需要在检查前喝造影剂吗. The more contrast you are able to drink, the better the images are for the radiologist to visualize your digestive tract.

ALLERGY如果您对任何造影剂有过敏反应，请在安排扫描时通知访问中心的工作人员. 如果您过去对任何造影剂有严重或过敏反应，则不需要静脉注射造影剂. 轻度到中度的反应需要一个计划，包括在CT检查之前服用药物. These plans will be discussed with you in detail when you schedule your exam. 任何已知的对造影剂的反应都应该和你的私人医生讨论.

EAT/DRINK: If your study was ordered without contrast, you can eat, drink and take your prescribed medications prior to your exam.

If your doctor orders a CT scan with contrast, do not eat anything three hours prior to your CT scan. We encourage you to drink clear liquids. You may also take your prescribed medications prior to your exam.

DIABETICS: People with diabetes should eat a light breakfast or lunch three hours prior to the scan time. Depending on your oral medication for diabetes, you may be asked to discontinue use of the medication for 48 hours after the CT examination. Detailed instructions will be given following your examination.

MEDICATION: All patients can take their prescribed medications as usual.

What are the risks of a CT scan?

如果你怀孕了或认为你可能怀孕了，你应该通知你的卫生保健提供者.

The amount of radiation dose used in a CT scan is small. 你可能需要向你的医生询问CT过程中使用的辐射量以及与你的特殊情况相关的风险.

如果你有幽闭恐惧症或容易变得焦虑，提前告诉你的医生. 在手术前，医生可能会给你开一种温和的镇静剂，让你感觉更舒服.

What happens during a CT scan?

CT扫描可以在门诊进行，也可以作为住院的一部分. Procedures may vary depending on your condition and your physician’s practices. Generally, CT scans follow this process:

• You may be asked to change into a patient gown. If so, a gown will be provided for you. A locker will be provided to secure all personal belongings. Please remove all piercings and leave all jewelry and valuables at home.
• If you are to have a procedure done with contrast, an IV line will be started in the hand or arm for injection of the contrast media. For oral contrast, you will be given a liquid contrast preparation to swallow. In some situations, the contrast may be given rectally.
• 你将躺在扫描台上，扫描台上滑进扫描机的一个大的圆形开口.
• The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. 扫描仪内的扬声器将使技术人员能够与你交流并听到你的声音. 你可能有一个呼叫按钮，这样你就可以让技术人员知道你在手术过程中有任何问题. 技术人员会一直看着你，并与你保持联系.
• As the scanner begins to rotate around you, X-rays will pass through the body for short amounts of time. You will hear clicking sounds, which are normal.
• 被人体组织吸收的x射线将被扫描仪检测并传输到计算机. 计算机将把这些信息转换成图像，供放射科医生解释.
• It is important that you remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.
• If contrast media is used for your procedure, you may feel some effects when the contrast is injected into the IV line. These effects include a flushing sensation, a salty or metallic taste in the mouth, a brief headache, or nausea and/or vomiting. These effects usually last for a few moments.
• You should notify the technologist if you have any breathing difficulties, sweating, numbness or heart palpitations.
• When the procedure has been completed, you will be removed from the scanner.
• If an IV line was inserted for contrast administration, the line will be removed.
• While the CT procedure itself causes no pain, 在整个手术过程中必须躺着不动可能会引起一些不适或疼痛, particularly in the case of a recent injury or invasive procedure, such as surgery. 技术人员将使用所有可能的舒适措施，并尽快完成手术，以尽量减少任何不适或疼痛.

What happens after a CT scan?

• If contrast media was used during your procedure, 您可能会被监测一段时间，以了解任何副作用或对比反应, such as itching, swelling, rash or difficulty breathing.
• If you notice any pain, 手术后回家后静脉注射部位出现红肿, you should notify your doctor, as this could indicate an infection or other type of reaction.
• There is typically no special type of care required after a CT scan. 你可以恢复你平常的饮食和活动，除非你的医生有不同的建议.
• Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.

What are some of the advances in CT technology?

Advances in CT technology include:

• High-resolution CT: This type of CT scan uses very thin slices (less than 0.1 inches), which are effective in providing greater detail in certain conditions, such as lung disease.
• Helical or spiral CT: During this type of CT scan, both the patient and the X-ray beam move continuously, with the X-ray beam circling the patient. The images are obtained much more quickly than with standard CT scans. 生成的图像具有更高的分辨率和对比度，提供更详细的信息. 多排螺旋CT扫描仪可用于获取心脏冠状动脉内钙积聚的信息.
• Ultrafast CT (also called electron beam CT): This type of CT scan produces images very rapidly, thus creating a type of "movie" of moving parts of the body, such as the chambers and valves of the heart. 这种扫描也可用于获取心脏冠状动脉内钙积聚的信息, but the helical scanners are much more common.
• Computed tomographic angiography (CTA): Angiography (or arteriography) is an X-ray image of the blood vessels. 例如，CT血管造影使用CT技术而不是标准的x射线或透视来获得血管图像, the coronary arteries of the heart.
• Combined positron emission tomography 和CT (PET/CT):将CT和正电子发射断层扫描技术结合到一台机器上称为PET/CT. PET/CT结合了CT提供详细解剖的能力和PET显示细胞功能和代谢的能力，以便在某些类型疾病的诊断和治疗中提供更高的准确性, particularly cancer. PET/CT may also be used to evaluate conditions such as epilepsy, Alzheimer’s disease and coronary artery disease.