Computed Tomography (CT), more commonly known as a CAT scan, is a form of medical diagnostic imaging that acquires detailed graphical images of the internal organs and parts of the body.

Joining separate images into one 3-D of graphical cross-section, CT scans show both body tissue and internal body organs, aiding the location of suspected cancer growth.
Computed Tomography is so detailed that it can show, and distinguish between, bone tissue, soft tissue, internal organs, muscles and tumors, empowering physicians with a unique tool to diagnose medical conditions and aid their treatment.

Using X-rays beams that pass through the body to measure how different tissues absorb different amounts of radiation, CT scans build an anatomical picture of an area of the body under investigation.

Computed Tomography is used in various medical situations where highly specific information is required to diagnoses a medical condition, such as the size, density and location of a tumor or malformation.

Computed Tomography is commonly used in Cancer diagnosis and treatment, where it is of great benefit in confirming the existence of a tumor, determining its size and location, and addressing the question of whether the cancer has spread.

Computed Tomography as a diagnostic imaging tool has huge potential due to its ability to provide painless, quick and detailed internal images of the body as well as being the only method that provides detailed images of bone, soft tissue, and blood vessels-allowing doctors to detect life-threatening conditions.

Frequently Asked CT Scan Questions

Who is a good Candidate for a CT scan?

Ct scans are designed to help identify medical conditions, diseases or traumas. CT scans are useful, then, for patients who have signs or symptoms of a particular condition, or for patients who have undergone injuries and are suspected of having internal damage or trauma. With a CT scan, a doctor can determine if a disease, trauma or other medical condition is present, and can take the next appropriate measure. People with symptoms have a higher probability of having a disease or condition than the general population. As well, symptoms usually indicate a more advanced form of a particular condition, meaning that the condition will likely be readily and easily detectable on CT images.

On a related note, CT scans can also help rule out certain medical conditions, diseases or traumas. A patient may be exhibiting signs or symptoms of a particular condition, but a CT scan may reveal that the condition does not exist. The doctor can thus eliminate that disease as a potential root of a problem. For example, a doctor may suspect a brain tumor in a patient who reports persistent dizziness and/or headache. A CT scan might reveal that a tumor is not present. Thus, the patient’s doctor can eliminate “brain tumor” as a possible root cause for the dizziness and headache, and can take measures to explore other possible conditions.

Finally, CT can be useful in situations where a medical condition is known and where further medical action is required. Such situations include:

• Planning a surgery
• Guiding a needle to obtain a biopsy (tissue sample)

In individuals where there is a known medical condition, a CT scan is an excellent way in determining:

• The extent of the problem
• The location of the problem
• The effect any treatment is having on the problem
  
  

How does a CT Scan work?

Ct uses a computer and rotating x-ray device to create detailed, cross-sectional images, or slices, of organs and body parts.

A CT machine resembles a large, square doughnut. A flat “patient couch” is situated in the circular opening, which is about 24 to 28 inches in diameter. The patient lies on the couch, which can be moved up, down, forward, and backward to position the patient for imaging.

The CT scanner itself is a circular, rotating frame with an x-ray tube mounted on one side and a banana-shaped detector mounted on the other. A fan-shaped beam of x-rays is created as the rotating frame spins the x-ray tube detector around the patient. For each complete rotation, one cross-sectional slice of the body is acquired.

As the scanner rotates, the detector takes numerous snapshots called “profiles.” Typically, about 1,000 profiles are taken in one rotation. Each profile is analyzed by computer, and the full set of profiles from each rotation is compiled into to form the slice-a two-dimensional image.

How do I prepare for a conventional CT Scan?

In general, no special preparation is required for a CT scan. Comfortable, loose clothing should be worn, although in some cases a patient may be asked to change into a hospital gown for the examination. It is also important to remove any metal prior to the exam: jewelry, dentures, eyeglasses, belt buckles, and metal zippers and buttons can interfere with the images.

A patient may be asked to limit eating and drinking to clear liquids, such as water, black coffee and tea, and broth for several hours prior to the appointment for a CT scan. This request will be dependent upon the facility and the type of examination.

For many CT examinations, a contrast agent (a liquid that enhances imaging of certain organs or blood vessels) will be administered. Depending on the type of examination, the contrast may be given orally, intravenously, or as an enema. If certain types of contrast will be used during as examination, the patient may be required to fast for several hours. If you are receiving the intravenous iodine contrast and you are 50years of age or older, have diabetes, or have any kidney problems you will be asked to get blood drawn for BUN and Creatinine Levels. Once we have these values we will be able to proceed with the exam

Do all CT Scans require the administration of a contrast agent?

Not all CT examinations require the use of a contrast agent. When a contrast agent is required, it is because the radiologist and referring physician determine that it is necessary for diagnosis. Contrast agents are considered to be safe and side effects are uncommon. The benefits associated with the improved imaging of particular organs generally outweigh the low risk of allergic reaction.

Intravenous Contrast

Intravenous contrast is used to highlight blood vessels and to enhance the structure of organs like the brain, spine, liver, and kidney. The contrast agent (usually an iodine compound) is clear, with a water-like consistency. Typically the contrast is contained in a special injector, which injects the contrast through a small needle taped in place during a specific period in the CT exam.

Once the contrast is injected into the bloodstream, it circulates throughout the body. The CT’s x-ray beam is weakened as it passes through the blood vessels and organs that have “taken up” the contrast. These structures are enhanced by this process and show up as white areas on the CT images. When the test is finished, the kidneys and liver quickly eliminate the contrast from the body.

Is Iodine a Safe Contrast Agent?

Iodine is considered to be a safe contrast agent. It has been used for many years without serious side effects. Because iodine contrast increases the visibility of target tissues on the images, the benefits are considered to outweigh the risks.

The most common side effect of iodine is a warm or “flushed” sensation during the actual injection of the iodine, followed sometimes by a metallic taste in the mouth that usually lasts for less than a minute. No treatment is necessary for this sensation, if experienced.

Another mild reaction is itching over various parts of the body. This reaction lasts from several minutes to a few hours after the injection. When this reaction occurs, medication is usually administered to counteract the itching.

More serious allergic reactions, while uncommon, include difficulty breathing and swelling of the throat or other parts of the body. These reactions, if experienced, are treated immediately.

Newer forms of contrast help to reduce the risk of an allergic reaction. If you have had an allergic reaction to iodine or a contrast agent in the past, the physician may recommend a steroid prep the day before the exam that will help prevent a reaction.

In some cases, CT can still provide valuable diagnostic information without the administration of a contrast agent, so the physician may decide this is the best course of action.

Oral CT Contrast

Oral contrast is used to highlight gastrointestinal (GI) organs in the abdomen and pelvis. If oral contrast will be used during an examination, the patient will be asked to fast for several hours before administration.

Gastrografin is a yellowish, water-based drink mixed with iodine, sometimes mixed with a variety of flavors also. It can have a bitter taste. This is the chosen oral contrast used at our site.

After the contrast is swallowed, it travels to the stomach and gastrointestinal tract. Like intravenous iodine, gastrografin weaken x-rays. On CT images, the organs that have “taken up” the contrast appear as highlighted white areas.

Is Oral Contrast Safe?

In general, gastrografin contrast is safe and pass uneventfully through the gastrointestinal tract. Minor and temporary side effects, such as constipation, may occur.

Rectal CT Contrast

Rectal contrast is used when enhanced images of the large intestine and other lower GI organs are required. The same types of contrast used for oral contrast are used for rectal contrast, but in different concentrations.

Rectal CT contrast is usually administered by enema. When the contrast is administered, the patient may experience mild discomfort, coolness, and a sense of fullness. After the CT is complete, the contrast is drained and the patient may go to the bathroom.

The preparation for rectal contrast is similar to oral contrast, in that the patient should be fasting for several hours before the test.

Is Rectal Contrast Safe?

Rectal contrast is considered to be safe and passes through the gastrointestinal tract uneventfully. Minor and temporary side effects, such as constipation, can occur.

What Happens During The Procedure?

If an intravenous contrast agent will be used, the procedure will be explained and the patient will be asked to sign a consent form. The needle will then be placed and taped down.

The technologist settles the patient on the scanner’s “couch.” The technologist glides the couch into place within the opening of the gantry, using cross-hair positioning lights to put the “target” area (for example, the chest) in the path of the x-rays.

After the patient is in position, the technologist usually leaves the CT room. The scanner is generally controlled by a computer in an adjacent room, which has a window facing the machine and patient. During this time, the technologist and patient can easily communicate through an intercom.

When images are being acquired, the patient is usually asked to hold his/her breath and remain motionless. Image acquisition typically lasts 18-30 seconds. When the scanner and patient couch move, the patient may hear whirring or clicking noises-this is normal. In addition, the scanner may tilt forward or back to capture images from the best angle during an examination of the head, sinus, inner ear, and spine.

It is very important to lie completely still while images are being taken. Any movement can reduce the clarity of the images, and the radiologist may then have difficulty interpreting them.

Will the CT Imaging Examination Hurt?

No, CT imaging itself should cause no pain. CT imaging requires that the patient remain still during the examination. For some patients, keeping still for some time may be uncomfortable. The CT examination itself causes no bodily sensation.

CT imaging examinations that require the patient to receive iodine contrast injection may cause slight, temporary discomfort while the intravenous needle is placed.

Is CT Imaging Safe?

Yes, CT imaging is considered a safe examination. In general, the diagnostic benefit of a CT scan usually outweighs the risk of x-ray radiation exposure or injections of imaging contrast. Patients should inform the radiologist or technologist if they have a history of allergies (especially to medications or previous iodine injections), diabetes, asthma, a heart condition, or kidney problems.

How Long Will the CT Examination Take?

Most CT departments or centers offer a wide array of computed tomography (CT) imaging examinations. Depending on the type of exam you will receive, the length of the actual procedure will typically be between 5-30 minutes.

Also, many CT exams require the patient to hold their breath several times. This helps to eliminate blurring from the images, which can be caused by breathing or other patient motion. Please discuss specific questions about the duration of your CT imaging examination with the technologist before your exam.

Do I need a Referral (prescription) to receive an CT Examination?

Yes, your doctor must give you a referral (prescription) in order for you to receive a computed tomography (CT) imaging examination. However, CT can often be performed on an outpatient basis without having to admit the patient to the hospital.

Can I Move While I am in the CT Scanner?

You should not move when you are on the CT table and the images are being acquired. It is important that you not move the body part being imaged, for example your head, until the entire CT exam is complete. CT exams of the chest and abdomen require the patient to hold their breath for a short period of time, for example, 10 to 30 seconds. This eliminates blurring in the image caused by breathing or other patient motion.

Can I Talk With Anyone During the CT Scan?

You may talk to the technologists or ask a question in between CT data acquisitions. You should not talk while the images are being acquired.

Can I Bring a Friend or a Relative into the CT Scan Room With Me?

No, CT uses x-ray and only the person being imaged should be in the CT scanner room during the examination.

If I am Nursing an Infant, Can I Breast Feed After an Injection of CT Contrast?

Typically, patients are instructed to wait for 24 hours after receiving the CT contrast injection before breast feeding again. Patients may wish to pump breast milk prior to the CT exam store it for use during this 24-hour period. Always check with the radiologist and the imaging center for their specific recommendations.

Can I Have a CT Imaging Exam if I am Pregnant?

Pregnant women should not have a CT exam or any x-ray examination, especially if the woman is in her first trimester (first 3 months of pregnancy). Depending on the condition, there may be other exams available, such as ultrasound, to help diagnose a medical condition. Pregnant women should always inform their imaging technologist or radiologist that they are pregnant, or may be pregnant.

What is the Difference between MRI and CT?

Both MRI and CT are diagnostic exams used to thoroughly image a selected area of the human body. Similarly, both MRI and CT require the use of a large machine, and each method relies upon computer technology to reconstruct a cross-sectional image of the body. Aside from these very fundamental similarities, there are many inherent differences between MRI and CT scans.

Magnetic Resonance Imaging (MRI) – Developed in the mid 1980’s, MRI technology utilizes radio frequency waves and very powerful magnets. After applying a very strong, localized electromagnetic field, the MRI scanner emits a series of radio pulses into the body, exciting the hydrogen protons found in the body’s soft tissue. Upon measuring the relaxation times of these hydrogen protons, the MRI scanner employs sophisticated computer technology to interpret the protons’ behavior and recreates a 3-dimensional image of the body. Since hydrogen is the most abundant element in the body, MRI technology is capable of producing amazingly clear images of organs and soft tissue. MRI is able to detect disease or injury in muscle structure along ligaments, and is used to assist in the visualization of  tumors. The ability to visualize soft-tissue and the vascular system make MRI an outstanding tool for imaging brain and spinal cord abnormalities. MRI is non-invasive, although certain studies may require the use of an intravenous contrast agent. MRI does not involve any ionizing radiation, and aside from a persistent thumping noise, patients will experience no discomfort or side effects.

Computerized Tomography (CT or CAT scan) – Developed in the 1970’s CT technology utilizes a highly sensitive X-ray beam that is focused on a specific part of the body. Upon passing through the body, the beam hits a detector, which relays this information into a computer. The computer analyzes the information based upon tissue density, and feeds it into a cathode ray tube. Like MRI, a cross-sectional representation (like “slices” of bread) of the body is produced. Bone shows up white, gases black, and tissue as varying shades of gray, depending on density. Generally, CT provides much better visualization of bone detail than MRI. CT scans provide excellent information on anatomical features and tissue density (this allows for the detection of tumors, and sometimes the ability to distinguish between malignant and benign tumors). CT scans can also detect calcium deposits, cysts, and abscesses. They are often used in place of ultrasound for obese patients because fat deposits often hinder ultrasonic waves.

What is the Difference between Conventional X-rays and CT scans?

X-rays are rays of electromagnetic radiation used to diagnosis and treat trauma and disease. When x-ray beams pass through the body, 2-dimentional images are created based on shadows made by body structures in the area being photographed. The image depends on the body structure’s absorption of the x-rays.

CT scans, meanwhile, produce 3-dimensional cross-section images of a particular body part. These images, too, are measures of x-ray absorption; however, many slices of the body join together to form an image. Typically, bone turns up white, air turns up black, and tissues and mucous turn up in shades of gray.

CT is more powerful and more detailed than conventional x-rays.