FREQUENTLY ASKED QUESTIONS
CT ~ MRI ~ Ultrasound ~
History of CT?
CT was discovered independently by a British engineer named Sir Godfrey Hounsfield and Dr. Alan Cormack. It has become a mainstay for diagnosing medical diseases. For their work, Hounsfield and Cormack were jointly awarded the Nobel Prize in 1979.
CT scanners first began to be installed in 1974. Because of advances in computer technology, CT scanners have vastly improved patient comfort because they are now much faster. These improvements have also led to higher-resolution images, which improve the diagnostic capabilities of the test. For example, the CT scan can show doctors small nodules or tumors, which they cannot see on an x-ray.
What are the risks of CT?
CT is a very low-risk procedure.
You will be exposed to radiation when undergoing a CT. However, it is a safe level.
The biggest potential risk is if you need to get a contrast (also called dye) injection. This can help distinguish normal tissues from abnormal tissues. It also helps to distinguish blood vessels from other structures such as lymph nodes.
Like any medication, some people can have a bad reaction to the contrast. The chance of a fatal reaction to the contrast is about 1 in 100,000. Those at increased risk may require special pretreatment. Anyone who has had a prior contrast reaction or severe allergic reaction to other medications, has asthma or emphysema, or has severe heart disease is at increased risk for a contrast reaction and is referred to a hospital x-ray department for the exam.
Any time an injection is done into a vein, there is a risk of the contrast leaking outside of the vein under the skin. If a large amount of contrast leaks under the skin, in rare cases, this can cause the skin to break down.How to prepare for CT?
If you are to have a contrast injection, you should not have anything to eat or drink for a few hours before your CT scan because the injection may cause stomach upset. To receive the contrast injection, an IV is inserted into your arm just prior to the scan. The contrast then enters your body through the IV.
Prior to most CT scans of the abdomen and pelvis, it is important to drink an oral contrast agent. This contrast agent helps the radiologist identify the gastrointestinal tract (stomach, small and large bowel), detect abnormalities of these organs, and to separate these structures from other structures within the abdomen. You will be asked to drink slightly less than a quart spread out over 1-2 hours.What happens during the CT Procedure?
Most CT scans are conducted as an outpatient procedure. You have the test and then go home.
“The CT scanner looks like a large donut with a narrow table in the middle, you rarely experience claustrophobia because of the openness of the doughnut shape of the scanner. Typically you lie on your back on the table, which moves through the center of the machine scanner, either head first or feet first, depending on the part of the body being scanned. For certain scans such as sinuses and middle ear, you would lie on your stomach and go through head first.
You must remain motionless for the length of the study, which is typically just a few minutes. The entire procedure, which includes set-up, the scan itself, checking the pictures, and removing the IV if needed, takes 15 minutes depending on what part of the body is being scanned.
o For some studies, you will be asked to hold your breath for a few seconds.
o No metal may be worn.
o What clothing you wear depends on the nature of the study. For a CT of the chest, abdomen, or pelvis, for example, usually you will change into a hospital gown. For a head CT, you can wear normal street clothes.
o Sedation is rarely necessary. The machine is quiet, so all you hear during the test is a quiet whirr.
o The technologist is in the next room and can observe you through a large window.
If you are pregnant, please notify your physician
ULTRASOUND
What is General Ultrasound Imaging?
Ultrasound imaging, also called ultrasound scanning or sonography, is a method of obtaining images from inside the human body through the use of high-frequency sound waves. The reflected sound wave echoes are recorded and displayed as a real-time visual image. No ionizing radiation (x-ray) is involved in ultrasound imaging. Obstetric ultrasound refers to the specialized use of sound waves to visualize and thus determine the condition of a pregnant woman and her embryo or fetus.
Ultrasound is a useful way of examining many of the body’s internal organs, including but not limited to the heart, liver, gallbladder, spleen, pancreas, kidneys, and bladder. Because ultrasound images are captured in real time, they can show movement of internal tissues and organs and enable physicians to see blood flow.
Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships at sea and anglers with fish detectors. As the sound passes through the body, echoes are produced that can be used to identify how far away an object is, how large it is, its shape and its consistency (fluid, solid or mixed).
What are the benefits vs. risks of ultrasound?
Benefits
o Ultrasound scanning is noninvasive (no needles or injections) and is usually painless.
o Ultrasound is widely available and easy to use.
o Ultrasound uses no ionizing radiation and is the preferred image modality for diagnosis and monitoring of pregnant women and their unborn infants.
o Ultrasound images can visualize structure, movement and live function in the body’s organs and blood vessels.
Risks
o For standard diagnostic ultrasound there are no known harmful effects on humans.How to prepare for ultrasound?
You should wear comfortable, loose-fitting clothing for your ultrasound exam. Other preparation depends on the type of examination you will have. For some scans, such as abdominal exam, your doctor may instruct you not to eat or drink for 6-8 hours before your appointment. For other scans, such as pelvic exam, you may be asked to drink up to six glasses of water two hours prior to your exam and avoid urinating so that your bladder is full when the scan begins.What happens during the ultrasound procedure?
Most ultrasound examinations are painless, fast and easy. You will lie on your back on an examining table. The technologist or doctor will spread some warm gel on your skin and then press the transducer against your body, moving it until the desired images are captured. The examination usually takes less than 30 minutes.MRI
What does MRI do for you and your medical team?
Magnetic Resonance Imaging (MRI) is one form of imaging modality used by physicians to look inside the human body to obtain clinically useful diagnostic information. Incorporating an advanced technology, MRI produces images of the anatomy without the use of radiation required with other imaging modalities such as x-ray and CT scanning.
MRI combines the physical properties of strong magnetic fields with radio waves to produce computer generated soft tissue images within any plane of the body. This widely used imaging technique can be used as a primary diagnostic tool to provide a quick and accurate diagnosis for your physician. In some situations, this procedure can reduce the need for further diagnostic procedures or invasive procedures such as exploratory surgery that may have associated complications.What are the benefits vs. risks of MRI?
MRI is a non-invasive procedure with no known side of after effects. The procedure is painless; in fact, you won’t see or feel anything. A faint knocking sound will be heard, which is simply the imaging process in operation.
The benefits of magnetic resonance imaging are many, with new applications continually being developed through on-going research. The procedure is used for all parts of the body and is effective in the clinical evaluation of the following conditions:
o Brain disorders
o Traumatic injuries
o Eye abnormalities
o Spine diseases
o Tumor detection
o Liver and other abdominal diseases
o Knee and shoulder injuries
o Musculoskeletal disorders
o Facial/Neck abnormalities
o Infection
o Cardiac malformations
o Blood flow and vessel disordersHow to prepare for MRI?
No special preparation is required prior to the MRI exam. You may eat normally and go about your daily routine. Continue to take any medication prescribed by your doctor unless otherwise directed.
Prior to entering the scan room for your exam, you will be asked to leave those items that are not compatible with a magnetic field in a safe place outside the scan room. A list of some of these items is listed below.
o Coins
o Jewelry
o Watches
o Glasses
o Credit cards
o Hearing aides
o Keys
o Hair pins
o Other metal objects
You may also be asked to remove make-up and dentures and to wear a hospital gown to avoid magnetic interference from belt buckles and zippers.
Once you are situated on the table, make sure you are comfortable so that it is easy to remain still for the duration of the examination. Breathe normally. Once the examination has begun, you will hear a knocking sound that represents changes in the magnetic field that are a normal part of the imaging process. At the conclusion of the exam, the technologist will assist you out of the scan room.
As mentioned previously, you will be asked to leave items that are incompatible with the magnetic field outside of the scan room. Other items to consider are the presence of implants and similar items. Check with your physician or MRI technologist if you have had any brain, ear, eye or other surgeries or any of the following:
o Pacemaker
o Neuro-stimulator (Tens-unit)
o Metal implants
o Intrauterine device (IUD), etc.
o Aneurysm clips
o Surgical staples
o Implanted drug infusion device
o Foreign metal objects in the eye
o Shrapnel or bullet wounds
Permanent eyeliner
If you are pregnant, please notify your physician.What happens during the MRI procedure?
A typical procedure averages 30 minutes, or longer depending on the type of information required by your physician. You can help to make your images spectacular by simply relaxing and remaining as still as possible during the exam. In fact, some patients fall asleep during the MRI exam.
During your MRI examination, a technologist will be with you and will be able to see you at all times. For your convenience, an intercom system is built into the MR imager so that if you need anything, the technologist will be right there.
In certain instances, a contrast agent may be administered to enhance the study. There are no extra precautions
if your physician requires this type of study.
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