A computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body.

Related tests include:

• Abdominal and pelvis CT scan
• Cranial or head CT scan
• Cervical, thoracic, and lumbosacral spine CT scan
• Orbit CT scan
• Chest CT scan

How the Test is Performed

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

Once 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 creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the body area can be created by stacking the slices together.

You must stay still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

Complete scans most often take only a few minutes. The newest scanners can image your entire body in less than 30 seconds.

How to Prepare for the Test

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

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 avoid another reaction.

Contrast can be given several ways, depending on the type of CT being performed.

• It may be delivered through a vein (IV) in your hand or forearm.
• You might drink the contrast before your scan. When you drink the contrast depends on the type of exam being done. The contrast liquid may taste chalky, although some are flavored. The contrast passes out of your body through your stools.
• Rarely, the contrast may be given into your rectum using an enema.

If contrast is used, you may also be asked not to eat or drink anything for 4 to 6 hours before the test.

Before receiving IV contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage). People taking this medicine may need to stop temporarily. Also let your provider know if you have any problems with your kidneys. The IV contrast can worsen kidney function.

Find out if the CT machine has a weight limit if you weigh more than 300 pounds (135 kilograms). Too much weight can damage the scanner.

You will need to remove jewelry and wear a hospital gown during the study.

How the Test will Feel

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

Contrast given through an IV may cause a slight burning feeling, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Why the Test is Performed

A CT scan creates detailed pictures of the body, including the brain, chest, spine, and abdomen. The test may be used to:

• Diagnose an infection
• Guide a surgeon to the right area during a biopsy
• Identify masses and tumors, including cancer
• Study blood vessels

Normal Results

Results are considered normal if the organs and structures being examined are normal in appearance.

What Abnormal Results Mean

Abnormal results depend on the part of the body being studied. Talk to your provider about questions and concerns.

Risks

Risks of CT scans include:

• Allergic reaction to the contrast dye
• Damage to kidney function from the contrast dye
• Exposure to radiation

CT scans expose you to 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 doctor should weigh this risk against the value of the information that will come from a CT scan. Most new CT scan machines have the ability to reduce the radiation dose.

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

• The most common type of contrast given into a vein contains iodine. If you have an iodine allergy, a type of contrast may cause nausea or vomiting, sneezing, itching, or hives.
• If you absolutely must be given such contrast, your doctor may give you antihistamines (such as Benadryl) or steroids before the test.
• Your kidneys help remove iodine from the body. You may need to receive extra fluids after the test to help flush iodine out of your body if you have diabetes or kidney disease.

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

Abdominal CT scan

Computed tomography scan – abdomen; CT scan – abdomen; CT abdomen and pelvis

An abdominal CT scan is an imaging method. This test uses x-rays to create cross-sectional pictures of the belly area. CT stands for computed tomography.

How the Test is Performed

You will lie on a narrow table that slides into the center of the CT scanner. Most often, you will lie on your back with your arms raised above your head.

Once 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 creates separate images of the belly area. These are called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the belly area can be made by stacking the slices together.

You must be still during the exam because movement causes blurred images. You may be told to hold your breath for short periods of time.

In many cases, an abdominal CT is done with a pelvis CT.

The scan should take less than 30 minutes.

How to Prepare for the Test

You need to have a special dye, called contrast, put into your body before some exams. Contrast helps certain areas show up better on the x-rays. Contrast can be administered in various ways. Such as:

• Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, you may also be asked not to eat or drink anything for 4 to 6 hours before the test.
• You may have to drink the contrast before the exam. When you drink it will depend on the type of exam being done. Contrast has a chalky taste, although some are flavored so they taste a little better. The contrast you drink will pass out of your body through your stools and is harmless.

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 safely receive this substance.

Before receiving the contrast, tell your provider if you take the diabetes medicine metformin. People taking this medicine may have to stop taking it for a while before the test.

Let your provider know if you have any kidney problems. The IV contrast can worsen kidney function.

Too much weight can damage the scanner. Find out if the CT machine has a weight limit if you weigh more than 300 pounds (135 kg).

You will need to take off your jewelry and wear a hospital gown during the study.

How the Test will Feel

Lying on the hard table may be a little bit uncomfortable.

If you have contrast through a vein (IV), you may have:

• Slight burning sensation
• Metallic taste in the mouth
• Warm flushing of the body

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

Why the Test is Performed

An abdominal CT scan makes detailed pictures of the structures inside your belly very quickly.

This test may be used to look for:

• Blood in the urine
• Cause of abdominal pain or swelling
• Cause of abnormal blood test results such as liver or kidney problems
• Hernia
• Cause of a fever
• Masses and tumors, including cancer
• Infections or injury
• Kidney stones
• Appendicitis

What Abnormal Results Mean

The abdominal CT scan may show some cancers, including:

• Cancer of the renal pelvis or ureter
• Colon cancer
• Hepatocellular carcinoma
• Lymphoma
• Melanoma
• Ovarian cancer
• Pancreatic cancer
• Pheochromocytoma
• Renal cell carcinoma (kidney cancer)
• Spread of cancers that began outside the belly

The abdominal CT scan may show problems with the gallbladder, liver, or pancreas, including:

• Acute cholecystitis
• Alcoholic liver disease
• Cholelithiasis
• Pancreatic abscess
• Pancreatic pseudocyst
• Pancreatitis
• Blockage of bile ducts

The abdominal CT scan may reveal the following kidney problems:

• Blockage of the kidneys
• Hydronephrosis (kidney swelling from the backflow of urine)
• Kidney infection
• Kidney stones
• Kidney or ureter damage
• Polycystic kidney disease

Abnormal results may also be due to:

• Abdominal aortic aneurysm
• Abscesses
• Appendicitis
• Bowel wall thickening
• Crohn disease
• Renal artery stenosis
• Renal vein thrombosis

Risks

Risks of CT scans include:

• Allergy to contrast dye
• Exposure to radiation
• Damage to kidney function from contrast dye

CT scans expose you to more radiation than regular x-rays. Many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. Most modern scanners are able to reduce the radiation exposure. Talk to your provider about this risk and the benefit of the test for getting a correct diagnosis of your medical problem.

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

The most common type of contrast given into a vein contains iodine. If you have an iodine allergy, you may have nausea or vomiting , sneezing , itching , or hives if you get this type of contrast. If you must be given such contrast, your provider may give you antihistamines (such as Benadryl) or steroids before the test.

Your kidneys help remove IV dye from the body. You may need extra fluids after the test to help flush the iodine out of your body if you have kidney disease or diabetes.

Rarely, the dye may cause a life-threatening allergic response. Tell the scanner operator right away if you have any trouble breathing during the test. Scanners come with an intercom and speakers, so the operator can hear you at all times.

Arm CT scan

CAT scan – arm; Computed axial tomography scan – arm; Computed tomography scan – arm; CT scan – arm

A computed tomography (CT) scan of the arm is an imaging method that uses x-rays to make cross-sectional pictures of the arm.

How the Test is Performed

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

Once 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 creates separate images of the arm area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the arm can be created by adding the slices together.

You must be still during the exam. Movement can cause blurred images. You may be told to hold your breath for short periods of time.

The scan should take only 10 to 15 minutes.

How to Prepare for the Test

For some tests, you will need to have a special dye, called contrast, 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 (IV) in your hand or forearm. If contrast is used, 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 in order to safely receive this substance.
• Before receiving the contrast, tell your provider if you take the diabetes drug metformin (Glucophage). You may need to take special steps if you are on this medicine.

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.

You will be asked to remove jewelry and wear a hospital gown during the study.

How the Test will Feel

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

Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These feels are normal. They will go away within a few seconds.

Why the Test is Performed

CT rapidly creates detailed pictures of the body, including the arms. The test may help detect or diagnose:

• An abscess or infection
• The cause of pain or other problems in the wrist, shoulder, or elbow joints (usually when MRI cannot be done)
• A broken bone
• Masses and tumors, including cancer

A CT scan may also be used to guide a surgeon to the right area during a biopsy.

Normal Results

Results are considered normal if no problems are seen in the images.

What Abnormal Results Mean

Abnormal results may be due to:

• An abscess (collection of pus)
• Blood clot in the arm (deep venous thrombosis)
• Bone tumors
• Cancer
• A broken or fractured bone
• Damage to the hand, wrist, or elbow joints
• Cyst

Risks

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans expose you to 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 weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

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

• The most common type of contrast given into a vein contains iodine. A person with an iodine allergy may have nausea or vomiting, sneezing, itching, or hives if given this type of contrast.
• If contrast is needed, you may get antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to get extra fluids after the test to help flush the iodine out of the body.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, let the scanner operator know right away. Scanners have intercom and speakers so the operator can hear you at all times.

Head CT scan

Brain CT; Cranial CT; CT scan – skull; CT scan – head; CT scan – orbits; CT scan – sinuses; Computed tomography – cranial; CAT scan – brain

A head computed tomography (CT) scan uses many x-rays to create pictures of the head, including the skull, brain, eye sockets, and sinuses.

How the Test is Performed

Head CT is done in the hospital or radiology center.

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

While inside the scanner, the machine’s x-ray beam rotates around you.

A computer creates separate images of the body area, called slices. These images can be:

• Stored
• Viewed on a monitor
• Printed on film

Three-dimensional models of the head area can be created by stacking the slices together.

You must be still during the exam because movement causes blurred images. You may be told to hold your breath for short periods.

A complete scan usually takes only 30 seconds to a few minutes.

How to Prepare for the Test

Certain CT exams require a special dye, called contrast material. It is delivered into the body before the test starts. Contrast helps certain areas show up better on x-rays.

• Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, 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 in order to safely receive it.
• Before receiving the contrast, tell your provider if you take the diabetes medicine metformin (Glucophage). You may need to take extra precautions. Also, let your provider know if you have any kidney function problems as the IV contrast can worsen this problem.

If you weigh more than 300 pounds (135 kg), find out if the CT machine has a weight limit. Some machines do.

You will be asked to remove the jewelry and may need to wear a hospital gown during the study.

How the Test will Feel

The x-rays produced by the CT scan are painless. Some people may have discomfort from lying on the hard table.

Contrast material given through a vein may cause a:

• Slight burning feeling
• Metallic taste in the mouth
• Warm flushing of the body

This is normal and usually goes away within a few seconds.

Why the Test is Performed

A head CT scan is recommended to help diagnose or monitor the following conditions:

• Birth (congenital) defect of the head or brain
• Brain infection
• Brain tumor
• The buildup of fluid inside the skull ( hydrocephalus )
• Injury (trauma) to the brain, head, or face
• Stroke or bleeding in the brain

It may also be done to look for the cause of:

• Abnormal head size in children
• Changes in thinking or behavior
• Fainting
• Headache, when you have certain other signs or symptoms
• Hearing loss (in some people)
• Symptoms of damage to part of the brain, such as vision problems, muscle weakness, numbness and tingling, hearing loss, speaking difficulties, or swallowing problems

What Abnormal Results Mean

Abnormal results may be due to:

• Abnormal blood vessels ( arteriovenous malformation )
• Bulging blood vessel in the brain (aneurysm)
• Bleeding (for example, subdural hematoma or bleeding in the brain tissue)
• Bone infection
• A brain abscess or infection
• Brain damage due to injury
• Brain tissue swelling or injury
• Brain tumor or other growth (mass)
• Loss of brain tissue (cerebral atrophy)
• Fluid collecting inside the skull ( hydrocephalus )
• Problems with the hearing nerve
• Stroke or transient ischemic attack (TIA)

Risks

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye
• Kidney damage from the contrast dye

CT scans use 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 weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

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

• 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, nausea or vomiting, sneezing, itching, or hives may occur.
• If you absolutely must be given such contrast, your provider may give you antihistamines (such as Benadryl) or steroids before the test to prevent an allergic reaction.
• The kidneys help remove iodine from the body. Those with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

In rare cases, the dye may 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 someone can hear you at all times.

Considerations

A CT scan can reduce or avoid the need for invasive procedures to diagnose problems in the skull. This is one of the safest ways to study the head and neck.

Other tests that may be done instead of a head CT scan include:

• MRI of the head
• Positron emission tomography (PET) scan of the head

Knee CT scan

CAT scan – knee; Computed axial tomography scan – knee; Computed tomography scan – knee

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

How the Test is Performed

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. These are called slices. 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. You may have to hold your breath for short periods of time.

The scan should take less than 20 minutes.

How to Prepare for the Test

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) in your hand or forearm. If contrast is used, 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.
• Before receiving the contrast, 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 the jewelry and wear a hospital gown during the CT exam.

How the Test will Feel

Some people may be uncomfortable lying on the hard table.

Contrast given through an IV may cause:

• Slight burning feeling
• Metallic taste in the mouth
• Warm flushing of the body

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

Why the Test is Performed

A CT scan can quickly create more detailed pictures of the knee than standard x-rays. The test may be used to detect:

• Abscess or infection
• Broken bone
• Examine fractures and pattern of fractures
• The cause of pain or other problems in the knee joint (usually when MRI can’t be done)
• Masses and tumors, including cancer

A CT scan may also be used to guide a surgeon to the right area during a biopsy.

Normal Results

Results are considered normal if no problems are seen.

What Abnormal Results Mean

Abnormal results may be due to:

• An abscess (collection of puss)
• Arthritis
• Broken bone
• Bone tumors or cancer

Risks

Risks of CT scans include:

• Exposure to radiation
• Allergy to contrast dye

CT scans give off more radiation than regular x-rays. 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. You may have nausea or vomiting, sneezing, itching, or hives if you have an iodine allergy.
• 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 iodine if you have kidney disease or diabetes.

Rarely, the dye may cause a serious allergic response called anaphylaxis. This can be life-threatening. 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.

Leg CT scan

CAT scan – leg; Computed axial tomography scan – leg; Computed tomography scan – leg; CT scan – leg

A computed tomography (CT) scan of the leg makes cross-sectional pictures of the leg. It uses x-rays to create the images.

How the Test is Performed

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

Once 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 creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional (3D) models of the leg can be created by adding the slices together.

You will need to lie still during the exam. Movement can cause blurred images. You may need to hold your breath for short periods of time.

The scan should take only 10 to 15 minutes.

How to Prepare for the Test

Some exams use a special dye, called contrast, that is put into your body before the test starts. Contrast helps certain areas show up better on the x-rays.

• Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, 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 in order to avoid this problem.
• Before having the contrast, tell your provider if you take the diabetes medicine metformin (Glucophage). You may need to take extra steps before the test if you take this drug.

Too much weight can cause damage to the scanner’s working parts. Find out if the CT machine has a weight limit if you weigh more than 300 pounds (135 kilograms).

You will wear a hospital gown during the study. You will need to take off all jewelry.

How the Test will Feel

Some people may be uncomfortable lying on the hard table.

Contrast given through an IV may cause a slight burning feeling, a metal taste in the mouth, and a warm flushing of the body. These feelings are normal and go away in a few seconds.

Why the Test is Performed

CT makes detailed pictures of the body very quickly. The test may help look for:

• An abscess or infection
• A mass that is felt during a physical exam
• The cause of pain or other problems in the foot, ankle, or knee joints (usually when an MRI cannot be done)
• A broken bone
• The pattern of the fractures
• Masses and tumors, including cancer

A CT scan may also be used to guide a surgeon to the right area during a biopsy.

Normal Results

Results are considered normal if the leg being examined looks ok.

What Abnormal Results Mean

Abnormal results may be due to:

• Abscess or infection
• Blood clot in the leg (deep venous thrombosis)
• A broken or fractured bone
• Cancer
• Damage to the knee, foot, or ankle joint
• Noncancerous bone tumor

Risks

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may raise your risk for cancer, but the risk from any one scan is small. Talk to your provider about this risk against the benefits of the test.

Some people have allergies to contrast dye. Let your provider know if you have ever had this type of reaction.

• The most common type of contrast given into a vein contains iodine. A person with an iodine allergy may have nausea or vomiting, sneezing, itching, or hives from this type of contrast.
• If you must have this type of contrast, you may get antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. People with kidney disease or diabetes may need to get extra fluids after the test to help flush the iodine out of the body.

The dye may cause a life-threatening allergic response called anaphylaxis. This is rare. Tell the scanner operator right away if you have any trouble breathing during the test. Scanners come with an intercom and speakers, so the operator can hear you at all times.

Lumbar spine CT scan

CAT scan – lumbar spine; Computed axial tomography scan – lumbar spine; Computed tomography scan – lumbar spine; CT – lower back

A computed tomography (CT) scan of the lumbar spine makes cross-sectional pictures of the lower back (lumbar spine). It uses x-rays to create the images.

How the Test is Performed

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

Once 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 creates separate images of the spine area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the spine area can be created by adding the slices together.

You must be still during the exam. Movement can cause blurred images. You may be told to hold your breath for short periods of time.

The scan should take only 10 to 15 minutes.

How to Prepare for the Test

Some exams use a special dye, called contrast that is put into your body before the test starts. Contrast helps certain areas show up better on the x-rays.

Contrast can be given in different ways.

• It may be given through a vein (IV) in your hand or forearm.
• It may be given as an injection into the space around the spinal cord.

If contrast is used, 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 in order to avoid this problem.

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.

You will be asked to remove jewelry and wear a hospital gown during the study.

How the Test will Feel

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

Contrast given through an IV may cause a slight burning feeling, a metal taste in the mouth, and a warm flushing of the body. These feelings are normal and go away in a few seconds.

Why the Test is Performed

CT rapidly makes detailed pictures of the lower back. The test may be used to look for:

• Birth defects of the spine in children
• Injury in the lower spine
• Spine problems when MRI cannot be used

This test can also be used during or after an x-ray of the spinal cord and spinal nerve roots (myelography) or an x-ray of the disk (discography).

Normal Results

Results are considered normal if no problems are seen in the lumbar region in the images.

What Abnormal Results Mean

Abnormal results may be due to:

• Birth defects of the spine
• Bone problems
• Fracture
• Lumbar disk herniation
• Lumbar spinal stenosis
• Spondylolisthesis

Risks

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans expose you to 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. Talk to your provider about this risk and how it weighs against the benefits of the test for your medical problem.

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

• 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, nausea or vomiting, sneezing, itching, or hives may occur.
• If you must have this type of contrast, you may get antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. People with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

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

Considerations

The lumbar CT scan is good for evaluating large herniated disks, but it can miss smaller ones. This test can be combined with a myelogram to get a better image of the nerve roots and pick up smaller injuries.

Pelvic CT scan

CAT scan – pelvis; Computed axial tomography scan – pelvis; Computed tomography scan – pelvis; CT scan – pelvis

A computed tomography (CT) scan of the pelvis is an imaging method that uses x-rays to create cross-sectional pictures of the area between the hip bones. This part of the body is called the pelvic area.

Structures inside and near the pelvis include the bladder, prostate, and other male reproductive organs, female reproductive organs, lymph nodes, and pelvic bones.

Single CT images are called slices. The images are stored on a computer, viewed on a monitor, or printed on film. Three-dimensional models of the body area can be created by stacking the slices together.

How the Test is Performed

You are asked to lie on a narrow table that slides into the center of the CT scanner.

Once you are inside the scanner, the machine’s x-ray beam rotates around you.

You must be still during the exam because movement causes blurred images. You may be told to hold your breath for short periods of time.

The scan should take less than 30 minutes.

How to Prepare for the Test

Certain exams require a special dye, called contrast media, to be delivered into the body before the test starts. The contrast helps certain areas show up better on the x-rays.

• Contrast can be given through a vein (IV) in your hand or forearm. Or you may be asked to drink a liquid form of contrast. If contrast is used, 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 in order to safely receive this substance.
• Before receiving the contrast, tell your provider if you take the diabetes medicine metformin (Glucophage) because you may need to take extra precautions.

If you weigh more than 300 pounds (135 kilograms), find out if the CT machine has a weight limit. Too much weight can damage the scanner’s working parts.

You will be asked to remove the jewelry and wear a hospital gown during the study.

How the Test will Feel

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

Contrast given through an IV may cause a slight burning sensation, 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.

Why the Test is Performed

CT rapidly creates detailed pictures of the body, including the pelvis and areas near the pelvis. The test may be used to diagnose or detect:

• Masses or tumors, including cancer
• The cause of pelvic pain
• Injury to the pelvis

This test may also help:

• Guide a surgeon to the right area during a biopsy or other procedures
• Your health care provider plan for surgery
• Plan radiation treatment for cancer

Normal Results

Results are considered normal if the organs of the pelvis that are being examined are normal in appearance.

What Abnormal Results Mean

Abnormal results may be due to:

• An abscess (collection of pus)
• Bladder stones
• Broken bone
• Cancer
• Diverticulitis

Risks

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans do expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk of cancer. But the risk from any one scan is small. You and your provider should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

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

• 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, nausea or vomiting, sneezing, itching, or hives may occur.
• If you absolutely must be given such contrast, you may be given antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

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

Shoulder CT scan

CAT scan – shoulder; Computed axial tomography scan – shoulder; Computed tomography scan – shoulder; CT scan – shoulder

A computed tomography (CT) scan of the shoulder is an imaging method that uses x-rays to create cross-sectional pictures of the shoulder.

How the Test is Performed

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

Once 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 creates separate images of the shoulder area. These are called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the shoulder area can be created by adding the slices together.

You must be still during the exam because movement causes blurred images. You may be told to hold your breath for short periods of time.

The scan should take only 10 to 15 minutes.

How to Prepare for the Test

Certain exams require a special dye, called contrast, 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 (IV) in your hand or forearm. If contrast is used, 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 in order to safely receive this substance.
• Before receiving the contrast, tell your provider if you take the diabetes medicine metformin (Glucophage) because you may need to take extra precautions.

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.

You will be asked to remove the jewelry and wear a hospital gown during the study.

How the Test Will Feel

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

Contrast given through an IV may cause a slight burning sensation, 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.

Why the Test is Performed

CT rapidly creates detailed pictures of the shoulder. The test may help diagnose or detect:

• A dislocation, fracture, or another shoulder injury
• Evaluate the soft tissue such as rotator cuff tendons
• Abscess or infection
• The cause of pain or other problems in the shoulder joint when MRI cannot be done
• Masses and tumors, including cancer

This test may also help guide a surgeon to the right area during a biopsy in the shoulder area.

Normal Results

Results are considered normal if the shoulder being examined is normal in appearance.

What Abnormal Results Mean

Abnormal results may be due to:

• An abscess (collection of pus)
• Bone tumors or cancer
• Dislocated shoulder
• Shoulder fracture
• Rotator cuff tears

Risks

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans do expose you to 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 weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

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

• 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, nausea or vomiting, sneezing, itching, or hives may occur.
• If you absolutely must be given such contrast, you may need to get antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.

Sinus CT scan

CAT scan – sinus; Computed axial tomography scan – sinus; Computed tomography scan – sinus; CT scan – sinus

A computed tomography (CT) scan of the sinus is an imaging test that uses x-rays to make detailed pictures of the air-filled spaces inside the face (sinuses).

How the Test is Performed

You will be asked to lie on a narrow table that slides into the center of the CT scanner. You may lie on your back, or you may lie face-down with your chin raised.

Once 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 creates separate images of the body area. These are called slices. The images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the body area can be created by stacking the slices together.

You need to stay still during the exam because movement causes blurred images. You may be told to hold your breath for short periods of time. Straps and pillows may be used to keep you still during the procedure.

The actual scan should take about 30 seconds. The entire process should take 15 minutes.

How to Prepare for the Test

For some tests, you will need to have a special dye, called contrast, 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 (IV) in your hand or forearm. If contrast is used, 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 in order to safely receive this substance.
• Let your provider know if you have kidney problems. Contrast may not be able to be used if this is the case.
• Before receiving the contrast, tell your provider if you take the diabetes medicine metformin (Glucophage). You may need to take extra steps to prepare.

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.

You will be asked to remove jewelry and wear a hospital gown during the scan.

How the Test will Feel

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

Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These feelings are normal. They will go away within a few seconds.

Why the Test is Performed

CT rapidly creates detailed pictures of the sinuses. The test may diagnose or detect:

• Birth defects in the sinuses
• Infection in the bones of the sinuses ( osteomyelitis )
• Injury to the face over the sinuses from trauma
• Masses and tumors, including cancer
• Nasal polyps
• The cause of repeated bloody noses ( epistaxis )
• Sinus infection ( sinusitis )

The results from this test may also help your provider plan for sinus surgery.

Normal Results

Results are considered normal if no problems are seen in the sinuses.

What Abnormal Results Mean

Abnormal results may be due to:

• Birth defects
• Bone fractures
• Cancer
• Polyps in the sinuses
• Sinus infection (sinusitis)

Risks

Risks of a CT scan include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans expose you to 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 very small. You and your provider should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

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

• The most common type of contrast given into a vein contains iodine. A person with an iodine allergy may have nausea or vomiting, sneezing, itching, or hives if given this type of contrast.
• If contrast is needed, you may be given antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to get extra fluids after the test to help flush the iodine out of the body.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, let the scanner operator know right away. Scanners have an intercom and speakers, so the operator can hear you at all times.