Computed Tomography – CT scan of the Foot
Your doctor may order a computed tomography examination to aid in the diagnosis and treatment of your foot and ankle problem. Computed Tomography (CT) imaging, also known as “CAT scanning” (Computed Axial Tomography), combines the use of a digital computer together with a rotating x-ray device to create detailed cross sectional images or “”slices”” of the different parts, particularly bony structures, of the foot and ankle. This test helps to delineate the structures of your foot and ankle and can give your doctor 3-D visualization of these structures to aid in your treatment. For many patients, CT can be performed on an outpatient basis without requiring admittance to a hospital. CT imaging is commonly ordered for the following foot pathologies:
During the procedure, you will lie very still on a table. This table passes your foot and ankle through the x-ray machine, which is shaped like a doughnut with a large hole. The machine, which is linked to a computer, rotates around the patient, taking pictures of one thin slice of tissue after another. The length of the procedure depends on the size of the area to be x-rayed. The computer then processes images from these x-rays. The final image, called a “computed tomogram” or “CT slice,” is displayed on a cathode-ray tube (CRT), a device similar to a television picture tube and screen. This image can be recorded permanently on film or can be stored on magnetic tape or optical disk.
Computed tomography offers some advantages over other x-ray techniques in diagnosing disease, particularly because it clearly shows the shape and exact location of soft tissues and bones in any “slice” of the foot and ankle. CT scans help doctors distinguish between a simple cyst and a solid tumor and any involvement of the bone. CT scanning is more accurate than conventional x-ray in determining the stage (extent) of some bone tumors. Information about the stage of the disease helps the doctor decide how to treat it.
Spiral CT scanners are one of the latest innovations. They use continuous scanning to generate cross-sectional slices and make a set of 3-dimensional images. Spiral CT has decreased the time it takes to produce tomographic pictures.
In preparing for the examination, you can eat and take your normal medications. The examination will take from 45 minutes to an hour based on the area being scanned. Patients are encouraged to bring something to read or do in case there are any delays prior to their CT exam. Patients should wear comfortable, loose fitting clothing for their CT exam. Some people may be concerned about the amount of radiation they receive during a CT scan. It is true that the radiation exposure from a CT scan is slightly higher than from a regular x-ray. Because of the radiation exposure, pregnant women should not have a CT exam or any x-ray examination, especially if the woman is in her first trimester (first of three-3 month periods 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.
Your physician will discuss the results with you. If you have any further questions regarding why this test was ordered for you, please ask your physician.
Electromyography (EMG) / Nerve Conduction Velocity( NCV)
This test is used to test the nerves and muscles in your entire lower extremity. Your doctor will usually order this test when he suspects that there may be some type of problem with the nerve supply to your foot and leg. Commonly the EMG/NCV test is used to diagnosis one of the following: Tarsal Tunnel Syndrome, Peripheral Neuropathy, Neuromuscular disorders, Nerve palsy or Paralysis, and Radioculopathy. Your doctor typically will refer you to either a hospital or a neurologist to have the test performed.
The EMG portion of the test is used to record the electrical activity in your muscles. It can diagnose diseases of the nerves and muscles. It can detect conditions such as tarsal tunnel syndrome, inflamed muscles and pinched nerves. A tiny needle, called an electrode, is inserted directly into a specific muscle belly. The electrode then records the activity during the insertion, while the muscle is at rest, and while the muscle contracts. Nerve and muscle diseases alter the pattern of electrical activity in these muscles, which is record both audibly and on a computer screen. After the first muscle is tested, the electrode may be inserted into another muscle. Muscles chosen for the testing vary with the patient’s symptoms and may be modified, depending on the results from the first muscles tested. Total testing time may range from just a few minutes to more than an hour, depending upon how many muscles are tested. After the exam, you may feel tenderness in the tested muscles. There is a slight risk of minor, localized inflammation in muscles during the test. This usually lasts only a few hours. Other common patient complaints are pain with insertion of the electrode.
Most of the time the Nerve Conduction Velocity Test will accompany the EMG Test. The NCV evaluates the health of the peripheral nerve by recording how fast an electrical impulse travels through it. A peripheral nerve transmits information between the spinal cord and the muscles. You will be resting on a cart or bed and electrodes will be taped to your skin. A stimulator will be held against your skin, which sends out a small electrical charge along the nerve. You may feel a tingle or your muscles may twitch but this shock is not harmful. Each test will take only a few minutes. After the exam the electrodes will be removed and your skin cleaned. The time between the stimulation and response will be recorded to determine how quickly and thoroughly that the impulse is sent. A number of nervous system diseases may reduce the speed of this impulse. Each nerve test takes just a few minutes to an hour, depending upon how many nerves are being tested.
While the hospital or neurologist’s office will give you instructions for the day of the examination, a few general preparations will help. Eat normally and take medication as you usually would. If you are taking a blood thinner, make sure you inform the testing facility and ask the ordering physician about the use of the medication and the timing of the test. Bath or shower the morning of the examination. Avoid bath oils or any skin lotions or emollients the day of the examination.
A typical EMG/NCV of the lower extremity takes approximately 45 minutes. This test is an important tool for diagnosing diseases of the nervous system, you can help ensure the best results if you relax and cooperate with the technicians. Make sure that you ask any questions that you have about the test before it is performed. Your physician will discuss the results with you. If you have any further questions regarding why this test was ordered for you, please ask your physician.
MRI – Magnetic Resonance Imaging
In some foot and ankle conditions, your doctor may order an MRI to help diagnosis the problem that you are having with your foot and ankle. In the foot and ankle, MRI can be used to diagnosis the following conditions:
1. Tendon injuries
2. Ligament injuries
3. Cartilage injuries
5. Tumors (soft tissue and bone)
7. Avascular necrosis
8. Non-unions or delayed unions of bone fractures
What is MRI?
MRI is the newest way to view the human body since the CT (CAT) scanner was invented. Unlike CT scans, MRI does not use radiation in the conventional sense of the word. Rather, it combines the use of a large magnet and radio waves. The hydrogen atoms in the patient’s body react to the magnetic field, and a computer analyzes the results and makes pictures of the inside of your body. MRI pictures show the soft tissues and bones of the foot and ankle in a cross sectional fashion. In many situations MRI offers unique information to help your doctor better plan your treatment and care.
During the scan you will be lying inside a large tubular donut-shaped machine. Typically only your leg will go into the machine and the rest of your body will be outside of the tube. The radiographers want you to be comfortable and will ask you to be very still during the scan because even slight movement can spoil the images and reduce their usefulness to you and your doctor. Because the MRI uses a large magnet to create the images during the exam, you will hear a series of loud knocking sounds. You must remain very still at this time, as this is when the pictures are being taken. The inside of the scanner is well lit, and has a fan to blow fresh air gently over you. Music is typically provided if needed and the radiographers will talk to you through an intercom system to tell you want is going on.
Preparation for MRI
In most cases there is no special preparation for an MRI scan. You can eat and drink normally on the day of the scan although it is best to avoid large amounts of coffee or other things that make you restless. It is very important not to bring any metal into the scan room without letting the Radiographer know. Before the scan you will be asked to remove your watch, keys, coins, credit cards, bus tickets and phone cards. The strong magnet of the MRI scanner can damage all these, or they might cause distortions in the MRI pictures. When you arrive at MRI, you will be asked a series of questions to find out if you have any metal or implants in your body.
Getting Comfortable & Keeping Still
MRI images are very sensitive to movement. By keeping very still during the scan you can improve the quality of the images that are obtained. We have found that the best way to keep still is to be relaxed, lying comfortably as if you were dropping off to sleep. The MRI Radiographer is very interested in making you comfortable in the scanner so that you feel settled, secure and relaxed, let them know what they can do for you and together you will ensure the best possible pictures.
Problems with MRI
It may not be possible, or safe, to have a MRI scan if you have any of these items:
Let the MRI Unit know well before your appointment if you have any of these. Experienced MRI staff will have to discuss the exact implant or metal with you to decide if it is safe to perform the scan. Deciding which implants cannot be scanned takes special knowledge and experience. Before the scan you will be asked a series of questions to check that it is safe for you to enter the scan room.
People with dental fillings and bridges, hip and knee replacements, and tubal ligation clips can all be scanned safely. The Radiographers will want to know about these things to minimize the effect they have on your images.
If you have experienced claustrophobia, or have trouble in enclosed spaces talk about it with the MRI staff before your appointment date. For mild claustrophobia, the staff can help you to relax enough to get rid of the anxiety in a few minutes. If your claustrophobia is severe you may need an anti-anxiety prescribed by your referring doctor. Staff at the MRI unit can be contacted about this and can offer your doctors some advice. You shouldn’t drive after taking such drugs, so arrange a safe way to get home. Because there are no side effects of MRI you can bring a friend into the scan room for support if that will help your anxiety. Children in particular should feel free to bring an adult in with them. Everyone coming into the scan room will be asked the questions about metal and implants.
Contrast Injections (Dye)
Most MRI tests do not need you to have an injection, but in some situations a contrast agent can greatly improve the accuracy of the scan. The contrast is injected into a vein, and the dose is quite small. MRI contrast is not the same as X-ray contrast. Very few people notice when it is injected. Make sure to tell the technologist if you have any allergies to contrast dye.
If you are pregnant or could be pregnant at the time of your scan appointment, please call us early so we can discuss the situation with you and consult your doctor. MRI causes a slight heating of your body, so most MRI sites avoid scanning during the first 3 months of pregnancy unless the diagnosis cannot wait and the only alternative test uses X-rays. Beyond that period, MRI is still avoided if the diagnosis can wait till your child is born as a matter of extreme caution. In many sites around the world MRI is used to examine pregnant women and their babies to avoid the need for X-ray tests. MRI contrast is not used during pregnancy.
How long does the MRI take?
Each test is specifically tailored to your needs. Several pictures may be needed to complete the exam. Each picture can take anywhere from a few seconds to fifteen minutes. A full exam of the foot and ankle could take anywhere from one hour to an hour and a half. The length of the exam depends on the area being tested and if any contrast is used.
MRI scans are usually not reported while you are at the MRI Unit. The images are filmed by the Radiographer who scans you, and then later interpreted by a specialist called a Radiologist. Their report is sent with the MRI films and any private films you brought along, to the doctor who referred you. This delivery usually takes several days.
Ultrasound Examination of the Foot and Ankle
Musculoskeletal ultrasonography is a very powerful diagnostic tool for the diagnosis of wide array of foot and ankle problems. Your physician may order an ultrasound or perform the ultrasound in their office to help diagnose your foot problem. Ultrasound is used typically for soft tissue problem, not bone conditions. Some of the foot disorders that ultrasound is used for are the following:
1. Foreign bodies
2. Morton’s neuroma
3. Soft tissue masses
4. Bursitis or capsulitis of the joints
5. Ligament injuries
6. Tendonitis or tendon tears
7. Heel spurs or plantar fasciitis
8. Tarsal tunnel syndrome
9. Ultrasound guided injection or aspirations
What is Ultrasound? Most people know about ultrasound to image a baby or a gallbladder, but it has growing application in musculoskeletal disorders. Ultrasound is based on sound waves. Sound waves are emitted from a transducer probe that is applied to the body and these sound waves will past into the body and then are reflected back to the transducer probe to be recorded. The recorded image is based on the density of the object that the sound waves encounter. An object with a high density appears white or brighter on the recorded image, while objects of low density will appear black or dark on the image. Intermediate densities will appear gray. The sound waves are recorded back to the machine, which will produce the image. This image will appear on the computer screen and is recorded permanently either by a hard copy film or video tape (if available) or both. A radiologist or your doctor will read these images and write a report on their findings.
Ultrasound is completely safe and painless. It also has no contraindications. There is no problem in having the examination if you are pregnant, have a pacemaker, or other medical conditions that may prevent you from having a MRI or CT scan. Ultrasound also does not produce any radiation as with a CT scan or x-rays.
In preparing for the examination, you can eat and take your normal medications. The examination will take from 45 minutes to an hour based on the area being scanned. It is advised that you bath the day of the examination but avoid the use of any skin lotions or emollients. Also you should where loose fitting clothing or shorts to make it easier to perform the examination. Your physician will discuss the results with you. If you have any further questions regarding why this test was ordered for you, please ask your physician.