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Learn More About Diagnostic Radiology
Heart & Vascular
Baylor provides a full array of diagnostic and therapeutic services at our hospitals and imaging centers across the Dallas/Fort Worth Metroplex. Learn important information about the procedures listed below, including why the tests are needed, what to expect and results and risks for each.
Some women are at greater risk for osteoporosis — the decrease of bone mass and density as a result of the depletion of bone calcium and protein — than others. Your doctor can help you determine your risk of developing osteoporosis by taking your personal and family medical history, and by performing a bone density test or bone mass measurement.
A bone density test, also known as bone mass measurement or bone mineral density test, measures the strength and density of your bones as you approach menopause and, when the test is repeated sometime later, can help determine how quickly you are losing bone mass and density. These tests are painless, noninvasive, and safe. They compare your bone density with standards for what is expected in someone of your age, gender, and size, and to the optimal peak bone density of a healthy young adult of the same gender. Bone density testing can help to:
Detect low bone density before a fracture occurs.
Confirm a diagnosis of osteoporosis if you have already fractured.
Predict your chances of fracturing in the future.
Determine your rate of bone loss and/or monitor the effects of treatment if the test is conducted at intervals of a year or more.
If you have 1 or more of the following risk factors for osteoporosis, you may want to consider having a bone density test:
You have already experienced a bone fracture that may be the result of thinning bones.
Your mother, grandmother, or another close relative had osteoporosis or bone fractures.
Over a long period of time, you have taken medication that accelerates bone loss, such as corticosteroids for treating rheumatoid arthritis or other conditions, or some anti-seizure medications.
You have low body weight, a slight build, or a light complexion.
You have a history of cigarette smoking or heavy drinking.
Bone density measurements are preformed in order to find or confirm a diagnosis of osteoporosis.
Mammography is an X-ray examination of the breast. It is used to detect and evaluate breast disease in women who either have breast problems such as a lump, pain, or nipple discharge, as well as for women who have no breast complaints. The procedure allows detection of breast cancers, benign tumors, and cysts before they can be detected by palpation (touch).
Mammography cannot prove that an abnormal area is cancer, but if it raises a significant suspicion of cancer, tissue will be removed for a biopsy. Tissue may be removed by needle or open surgical biopsy and examined under a microscope to determine if it is cancer.
The development of digital mammography technology allows for improved breast imaging, in particular, for women less than 50 years of age, women with dense breast tissue, or women who are premenopausal or perimenopausal. Digital mammography provides electronic images of the breasts that can be enhanced by computer technology, stored on computers, and even transmitted electronically in situations where remote access to the mammogram is required. The procedure for a digital mammography is basically performed the same way as a standard mammogram.
With computer-aided detection (CAD) systems, a digitized mammographic image from a conventional film mammogram or a digitally acquired mammogram is analyzed for masses, calcifications, or areas of abnormal density that may indicate the presence of cancer. The images are highlighted by the CAD system for further analysis by the radiologist.
X-rays use invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film. Standard X-rays are performed for many reasons, including diagnosing tumors or bone injuries.
X-rays are made by using external radiation to produce images of the body, its organs, and other internal structures for diagnostic purposes. X-rays pass through body structures onto specially-treated plates (similar to camera film) and a "negative" type picture is made (the more solid a structure is, the whiter it appears on the film).
Each breast has 15 to 20 sections, called lobes, which are arranged like the petals of a daisy. Each lobe has many smaller lobules, which end in dozens of tiny bulbs that can produce milk.
The lobes, lobules, and bulbs are all linked by thin tubes called ducts. These ducts lead to the nipple in the center of a dark area of skin called the areola. Fat fills the spaces between lobules and ducts.
There are no muscles in the breast, but muscles lie under each breast and cover the ribs.Each breast also contains blood vessels and vessels that carry lymph. The lymph vessels lead to small bean-shaped organs called lymph nodes, clusters of which are found under the arm, above the collarbone, and in the chest, as well as in many other parts of the body.
A screening mammogram is an X-ray of the breast used to detect breast changes in women who have no signs of breast cancer. It usually involves two X-rays of each breast. Using a mammogram, it is possible to detect a tumor that cannot be felt.
A diagnostic mammogram is an X-ray of the breast used to diagnose unusual breast changes, such as a lump, pain, nipple thickening or discharge, or a change in breast size or shape.
A diagnostic mammogram is also used to evaluate abnormalities detected on a screening mammogram. It is a basic medical tool and is appropriate in the work-up of breast changes, regardless of a woman's age.
Mammography has been used for about 30 years, and in the past 15 years technical advancements have greatly improved both the technique and results. Today, specialized equipment, used only for breast X-rays, produce studies that are high in quality but low in radiation dose.
Mammography may be used either for screening or to evaluate possible abnormalities discovered by palpation, screening mammography, or other means. Women older than 25 years should undergo diagnostic mammography if they have symptoms such as a palpable lump, breast skin thickening or indentation, nipple discharge or retraction, an erosive sore of the nipple, or breast pain.
A mammogram may be used to evaluate breast pain when physical examination and history are not conclusive. Women with breasts that are dense, "lumpy," and/or very large may be screened with mammography, as physical examination may be difficult to perform.
Women who are at high risk for breast cancer or with a history of breast cancer may be routinely screened with mammography.
The following screening guidelines are for early detection of cancer in women who have no symptoms:
Experts have different recommendations for mammography. Currently, the U.S. Preventive Services Task Force (USPSTF) recommends screening every two years for women ages 50 to 74. The American Cancer Society (ACS) recommends yearly screening for all women ages 40 and older. Women should talk with their health care providers about their personal risk factors before making a decision about when to start getting mammograms or how often they should get them.
The ACS recommends clinical breast exams (CBEs) at least every three years for all women in their 20s and 30s. A CBE is an inspection of the breasts by a health care provider, who will look at and feel (palpate) the breasts to detect any lumps. The ACS recommends annual CBEs for women ages 40 and older. The USPSTF, however, believes there is not enough evidence to assess the value of CBEs for women ages 40 and older. Women should talk with their health care providers about their personal risk factors and make a decision about whether they should have a CBE.
The USPSTF does not recommend breast self-exams (BSEs) because evidence suggests BSEs do not lower risk for death from breast cancer. The ACS says BSEs are an option for women 20 and older as a means of familiarizing themselves with their breasts so they can notice changes more easily. Talking with your health care provider about the benefits and limitations can help you decide if you should start performing BSEs.
Women who are at an increased risk (family history, genetic tendency, past breast cancer) should talk with their health care providers about the benefits and limitations of starting mammography screening earlier, having additional tests (breast ultrasound, MRI), or having more frequent exams.
In addition, the following guidelines by age are recommended:
National Cancer Institute Guideline for Screening Mammography. Women in their 40s and older should have a screening mammogram on a regular basis, every one to two years.
American Cancer Society Guideline for Screening Mammography. Women 40 years of age and older should have a screening mammogram every year.
Consult your health care provider regarding the screening guidelines that are appropriate for you.
A mammogram helps to identify the following conditions:
Calcifications. These are tiny mineral deposits within the breast tissue. There are two categories of calcifications:
Macrocalcifications. These are coarse calcium deposits that usually indicate degenerative changes in the breasts, such as the following:
Aging of the breast arteries
Microcalcifications. These are tiny (less than 1/50 of an inch) specks of calcium. When many microcalcifications are seen in one area, they are referred to as a cluster.
Masses. These may occur with or without associated calcifications, and may be due to different causes, including the following:
Cyst. A noncancerous collection of fluid in the breast. Cysts cannot be diagnosed by physical examination alone or by mammography alone. Either breast ultrasound or aspiration with a needle is required. If a mass is not a cyst, then further imaging may be necessary.
Benign breast conditions. Masses can be monitored with periodic mammography, but others may require immediate or delayed biopsy. About 80 percent of all breast changes that are biopsied are found to be benign (noncancerous) when looked at under the microscope.
Usually, a mammogram is done on an outpatient basis, although it can be part of inpatient care. There is no specific preparation for the examination. However, a woman should not wear deodorant, powders, or lotions under the arms on the day of the examination, as these substances can interfere with the images. If you have breast implants, be sure to tell your mammography facility that you have them when you make your appointment. You will need an X-ray technologist who is trained in working with patients with implants. This is important because breast implants can hide some breast tissue, which could make it difficult for the radiologist to see breast cancer when looking at your mammogram images.
Although each facility may have specific protocols in place, generally, a mammogram procedure follows this process:
The patient should describe any symptoms or problems to the technologist prior to the examination (if any).
The patient will undress from the waist up and will be given a gown to wear.
The patient will be positioned at the mammography unit, seated, standing, or lying down.
The breast will be positioned between two plates of the mammography unit, and pressure applied to compress the tissue. (This may produce temporary discomfort.) Breast compression is necessary in order to obtain the best image with the least amount of radiation possible.
The patient will be asked to hold her breath for a few seconds while the X-rays are taken.
The technologist will step behind a protective window and the image will be taken.
Each breast may be X-rayed at least two times from above and from the side positions to produce the films for the doctor to review.
After the X-rays are made, the patient will be asked to wait for a short time until the radiologist can review the films to determine if additional X-rays are necessary.
The examination process takes approximately 20 to 30 minutes.
This tests uses x-ray pictures used to find tumors in the breast and determine malignancy.
A myelogram, also known as myelography, is a diagnostic imaging procedure performed by a radiologist. It combines the use of a contrast substance with X-rays or computed tomography (CT) to evaluate abnormalities of the spinal canal, including the spinal cord, nerve roots, and other tissues.
The contrast (also called X-ray dye) is injected into the subarachnoid space within the spinal column before the procedure. This substance outlines the structures and causes the tissue under study to be visible.
After the contrast is injected it appears on an X-ray screen allowing the radiologist to view the spinal cord, subarachnoid space, and other surrounding structures more clearly than with standard X-rays of the spine.
The radiologist will also use a CT scan when performing a myelogram. A CT or CAT scan is a diagnostic imaging procedure using a combination of X-rays and computer technology to produce horizontal, or axial, images of the body. These images, called slices, show detailed images of the spinal canal. CT scans provide more detail than standard X-rays.
The spinal column is made up of 33 vertebrae that are separated by spongy disks and classified into distinct areas.
The cervical area consists of seven vertebrae in the neck.
The thoracic area consists of 12 vertebrae in the chest area.
The lumbar area consists of five vertebrae in the lower back area.
The sacrum has five, small fused vertebrae.
The four coccygeal vertebrae fuse to form one bone, called the coccyx or tailbone.
The spinal cord, a major part of the central nervous system, is located in the vertebral canal and reaches from the base of the skull to the upper part of the lower back. The bones of the spine and a sac containing cerebrospinal fluid surround it. The spinal cord carries sensory and movement signals to and from the brain and controls many reflexes.
A myelogram may be performed to assess the spinal cord, subarachnoid space, or other structures for abnormalities, particularly when another type of examination, such as a standard X-ray, is inconclusive. Myelograms may be used to evaluate many diseases, including, but not limited to, the following:
Spinal cord or brain tumors
Degenerative disc disease
Cysts. Benign capsules that may be filled with fluid
Tearing away or injury of spinal nerve roots
Arachnoiditis. Inflammation of a delicate membrane covering the brain
There may be other reasons for your doctor to recommend a myelogram.
You may want to ask your doctor about the amount of radiation used during the procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time.
If you are pregnant or suspect that you may be pregnant, you should notify your doctor. Radiation exposure to the fetus may cause birth defects.
Because a contrast dye is used during the procedure, there is risk of allergic reaction to the substance. You will need to let your doctor know if you have ever had a reaction to any contrast. A reported seafood allergy is not considered to be a contraindication for iodinated contrast.
Because the contrast is injected into the cerebrospinal fluid which also surrounds the brain, there is a small risk of seizure after the injection. Some medications may place you at greater risk for seizure and you may be asked to stop taking a medication for 48 hours before and after the study.
Because this procedure involves a lumbar puncture, the following potential complications may occur:
A small amount of CSF can leak from the needle insertion site. This can cause headaches after the procedure. If there is a persistent leak the headache can be severe.
There is a slight risk of infection because the needle breaks the skin's surface, providing a possible portal of entry for bacteria.
A temporary numbness to the legs or lower back pain may be experienced.
There is a risk of bleeding in the spinal canal.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.
Your doctor will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.
You will be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.
Generally, fasting is required prior to administering contrast. Your doctor will instruct you prior to the procedure of any necessary fasting requirements.
Notify the radiologist if you have ever had a reaction to any contrast or if you are allergic to iodine.
Notify the radiologist if you are pregnant or suspect that you may be pregnant.
Notify your doctor of all medications (prescribed and over-the-counter) and herbal supplements that you are taking. Many medications can cause problems with myelography. You will be screened for any of these before your test. You may be asked to stop some of your medications prior to the procedure.
Sedation may be given prior to the procedure to help you relax.
Notify the doctor if you have a history of seizures or if you are taking any prescribed medications for seizures.
Notify your doctor if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. It may be necessary for you to stop these medications prior to the procedure.
If the procedure is performed on an outpatient basis, you may be asked to remain in the hospital for several hours following the procedure. You should plan to have another person drive you home.
Based on your medical condition, your doctor may request other specific preparation.
A myelogram may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.
Generally, a myelogram follows this process:
You will be asked to remove any clothing, jewelry or other objects that may interfere with the procedure.
You will be given a gown to wear.
You will be reminded to empty your bladder prior to the start of the procedure.
During the procedure, you will lie on your stomach on the fluoroscopy table.
Your back will be cleansed with an antiseptic solution and draped with sterile towels.
The radiologist will anesthetize the skin by injecting a local anesthetic that numbs the site. This injection may sting for a few seconds, but makes the procedure less painful.
A needle will be inserted through the numbed skin and into the subarachnoid space where the spinal fluid is located. You may feel some pressure while the needle is inserted, but you must remain still during the insertion of the needle.
The radiologist will remove some of the spinal fluid from the spinal canal. Next, a portion of contrast dye will be injected into the spinal canal through the needle.
The X-ray table will be tilted in various directions to allow gravity to move the contrast dye to different areas of your spinal cord. You will be held in place by a special brace or harness. More contrast may be administered during this process through the secured lumbar puncture needle.
The needle is then removed and required X-rays or CT scan pictures will be taken.
You should notify the radiologist if you feel any numbness, tingling, headache, or lightheadedness during the procedure.
You may experience discomfort during the myelogram. The radiologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.
You should remain in the lying position for several hours after the procedure to reduce your risk of developing a CSF leak.
You will be asked to drink additional fluids to rehydrate after the procedure. This helps to replace the spinal fluid that was withdrawn and reduces the chance of developing a headache.
A nurse will monitor your vital signs (blood pressure, temperature, pulse, and respirations) frequently after the test. Analgesic agents may be administered if you develop a headache.
When you have completed the recovery period, you will be taken to your hospital room or discharged to your home.
Once you are at home, notify your doctor of any abnormalities, such as numbness and tingling of the legs, blood or other drainage from the injection site, pain at or near the injection site, inability to urinate, fever, stiff neck, or headaches. If the headaches persist for more than 24 hours after the procedure, or when you change positions, you should contact your doctor.
You may be instructed to limit your activity for 24 hours following the procedure. Generally, if no complications occur, you may return to your normal diet and activities.
Your doctor may give you additional or alternative instructions after the procedure, depending on your particular situation.
The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your doctor. Please consult your health care provider with any questions or concerns you may have regarding your condition.
This page contains links to other websites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these websites, nor do these sites endorse the information contained here.
American Academy of Neurological and Orthopaedic Surgeons
American Academy of Orthopaedic Surgeons
National Cancer Institute (NCI)
National Institute of Neurological Disorders and Stroke
National Institutes of Health (NIH)
National Library of Medicine
Myelograms use dye and x-rays to create an image of the spaces in between your spine.
X-rays use invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film or digital media. Standard X-rays are performed for many reasons, including diagnosing tumors or bone injuries.
X-rays are made by using external radiation to produce images of the body, its organs, and other internal structures for diagnostic purposes. X-rays pass through body structures onto specially-treated plates (similar to camera film) or digital media and a "negative" type picture is made (the more solid a structure is, the whiter it appears on the film).
When the body undergoes X-rays, different parts of the body allow varying amounts of the X-ray beams to pass through. The soft tissues in the body (such as blood, skin, fat, and muscle) allow most of the X-ray to pass through and appear dark gray on the film or digital media. A bone or a tumor, which is more dense than soft tissue, allows few of the X-rays to pass through and appears white on the X-ray. When a break in a bone has occurred, the X-ray beam passes through the broken area and appears as a dark line in the white bone.
X-ray technology is used in other types of diagnostic procedures, such as arteriograms, computed tomography (CT) scans, and fluoroscopy.
Radiation during pregnancy may lead to birth defects. Always tell your radiologist or doctor if you suspect you may be pregnant.
X-rays can be performed on an outpatient basis, or as part of inpatient care.
Although each facility may have specific protocols in place, generally, an X-ray procedure follows this process:
The patient will be asked to remove any clothing or jewelry which might interfere with the exposure of the body area to be examined. The patient will be given a gown to wear if clothing must be removed.
The patient is positioned on an X-ray table that carefully positions the part of the body that is to be X-rayed--between the X-ray machine and a cassette containing the X-ray film or specialized image plate. Some examinations may be performed with the patient in a sitting or standing position.
Body parts not being imaged may be covered with a lead apron (shield) to avoid exposure to the X-rays.
The X-ray beam will be aimed at the area to be imaged.
The patient must be very still or the image will be blurred.
The technologist will step behind a protective window and the image is taken.
Depending on the body part under study, various X-rays may be taken at different angles, such as the front and side view during a chest X-ray.
X-Ray & Fluoroscopy
A machine send x-ray particles through the body, creating a picture that is captured on a special type of film.
A CT or CAT scan is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan 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. A plate behind the body part captures the variations of the energy beam after it passes through skin, 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 computed tomography, the X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure, and provides much greater detail. The X-ray information is sent to a computer that interprets the X-ray data and displays it in two-dimensional form on a monitor. Newer technology and computer software makes three-dimensional (3-D) images possible.
CT scans may be done with or without contrast. "Contrast" refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure.
CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage.
You may want to ask your doctor about the amount of radiation used during the CT procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time. If you are pregnant or suspect that you may be pregnant, you should notify your doctor.
Advances in computed tomography technology include the following:
High-resolution computed tomography. This type of CT scan uses very thin slices (less than one-tenth of an inch), which are effective in providing greater detail in certain conditions such as lung disease.
Helical or spiral computed tomography. 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. The resulting images have greater resolution and contrast, thus providing more detailed information. Multidetector row helical CT scanners may be used to obtain information about calcium build-up inside the coronary arteries of the heart.
Ultrafast computed tomography (also called electron beam computed tomography). 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. This scan may also be used to obtain information about calcium build-up inside the coronary arteries of the heart, but the helical scanners are much more common.
Computed tomographic angiography (CTA). Angiography (or arteriography) is an X-ray image of the blood vessels. A CT angiogram uses CT technology rather than standard X-rays or fluoroscopy to obtain images of blood vessels, for example, the coronary arteries of the heart.
Combined computed tomography and positron emission tomography (PET/CT). The combination of computed tomography and positron emission tomography technologies into a single machine is referred to as PET/CT. PET/CT combines the ability of CT to provide detailed anatomy with the ability of PET to show cell function and metabolism to offer greater accuracy in the diagnosis and treatment of certain types of diseases, particularly cancer. PET/CT may also be used to evaluate epilepsy, Alzheimer's disease, and coronary artery disease.
Studies show that 85 percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your doctor know if you have ever had a reaction to any contrast dye, and/or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast. If you have any medical conditions or recent illnesses, inform your doctor. The effects of kidney disease and contrast agents have attracted increased attention over the last decade, as patients with kidney disease are more prone to kidney damage after contrast exposure. If you are pregnant or think you may be pregnant, you should notify your health care provider. If you are claustrophobic or tend to become anxious easily, tell your doctor ahead of time, as he or she may prescribe a mild sedative for you before the procedure to make you more comfortable. It will be necessary for you to remain still and quiet during the procedure, which may last 10 to 20 minutes.
CT scans can be performed on an outpatient basis, unless they are part of a patient's inpatient care. Although each facility may have specific protocols in place, generally, CT scans follow this process:
When the patient arrives for the CT scan, he or she will be asked to remove any clothing, jewelry, or other objects that may interfere with the scan.
If the patient will be having a procedure done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast medication. For oral contrast, the patient will be given the contrast material to swallow.
The patient will lie on a scan table that slides into a large, circular opening of the scanning machine.
The CT staff will be in another room where the scanner controls are located. However, the patient will be in constant sight of the staff through a window. Speakers inside the scanner will enable the staff to communicate with and hear the patient. The patient may have a call bell so that he or she can let the staff know if he or she has any problems during the procedure.
As the scanner rotates around the patient, X-rays will pass through the body for short amounts of time. The motion is hidden inside the gantry, the doughnut-shaped part of the machine. The patient may hear buzzing, whirring, and clicking as the X-ray tube rotates.
The X-rays absorbed by the body's tissues will be detected by the scanner and transmitted to the computer.
The computer will transform the information into an image to be interpreted by the radiologist.
It is very important that the patient remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.
The technologist will be watching the patient at all times and will be in constant communication.
The patient may be asked to wait for a short period of time while the radiologist examines the scans to make sure they are clear. If the scans are not clear enough to obtain adequate information, the patient may need to have additional scans performed.
Computerized tomography scans are used in order to get a quick and detailed picture of the brain, chest, spine or stomach.
MRI is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. MRI does not use ionizing radiation, as do X-rays and computed tomography (CT scans).
The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient and sends pulses of radio waves from a scanner. The strong magnetic field causes the hydrogen atoms in your body to align along the same axis. The radio waves knock the nuclei of the atoms in your body out of this aligned position. As the nuclei realign back into proper position, they send out radio signals. These signals are received by a computer that analyzes and converts them into an image of the part of the body being examined. This image appears on a viewing monitor. Cross-sectional views can be obtained to reveal further details. Some MRI machines look like narrow tunnels, while others are more open.
Magnetic resonance imaging (MRI) may be used instead of computed tomography (CT) in situations where organs or soft tissue are being studied, because MRI is better at telling the difference between different types of soft tissues, as well as the difference between normal and abnormal soft tissues..
Because ionizing radiation is not used, there is no risk of exposure to ionizing radiation during an MRI procedure.
Due to the use of the strong magnet, MRI cannot be performed on most patients with implanted pacemakers, older intracranial aneurysm clips, cochlear implants, certain prosthetic devices, implanted drug infusion pumps, neurostimulators, bone-growth stimulators, certain intrauterine contraceptive devices, or any other type of iron-based metal implants. MRI is also not recommended for people who have internal metallic objects such as bullets or shrapnel, as well as most surgical clips, pins, plates, screws, metal sutures, or wire mesh in their bodies. Dyes used in tattoos may contain iron and potentially could heat up during an MRI, but this is a rare occurrence.
Newer uses and indications for MRI have contributed to the development of additional magnetic resonance technology. Magnetic resonance angiography (MRA) is a procedure used to evaluate blood flow through arteries in a noninvasive (the skin is not pierced) manner. MRA can also be used to detect aneurysms within the brain and vascular malformations (abnormalities of blood vessels within the brain, spinal cord, or other parts of the body).
Magnetic resonance spectroscopy (MRS) is another noninvasive procedure used to assess chemical abnormalities in body tissues such as the brain. MRS may be used to assess disorders, such as HIV infection of the brain, stroke, head injury, coma, Alzheimer's disease, tumors, and multiple sclerosis.
Functional magnetic resonance imaging of the brain (fMRI) is used to determine the specific location within the brain where a certain function, such as speech or memory, occurs. The general areas of the brain in which such functions occur are known, but the exact location may vary from person to person. During functional resonance imaging of the brain, you will be asked to perform a specific task, such as recite the Pledge of Allegiance, while the scan is being done. By pinpointing the exact location of the functional center in the brain, doctors can plan surgery or other treatments for a particular disorder of the brain.
Another advance in MRI technology is the "open" MRI. Standard MRI units have a closed cylinder-shaped tunnel into which the patient is placed for the procedure. Open MRI units do not completely surround the patient, and some units may be open on all sides. Open MRI units are particularly useful for procedures involving:
Children. Parents or other caregivers may stay with a child during the procedure to provide comfort and security.
Claustrophobia. Before the development of open MRI units, persons with severe claustrophobia often required a sedative medication prior to the procedure.
Very large or obese persons. Almost anyone can be accommodated in most open MRI units.
An MRI may be performed on an outpatient basis, or as part of inpatient care. Although each facility may have specific protocols in place, generally, an MRI procedure follows this process:
Because of the strong magnetic field, the patient must remove all jewelry and metal objects, such as hairpins or barrettes, hearing aids, eyeglasses, and dental pieces.
If a contrast medication and/or sedative are to be given by an intravenous line (IV), an IV line will be started in the hand or arm. If the contrast is to be taken by mouth, the patient will be given the contrast to swallow.
The patient will lie on a table that slides into a tunnel in the scanner.
The MRI staff will be in another room where the scanner controls are located. However, the patient will be in constant sight of the staff through a window. Speakers inside the scanner will enable the staff to communicate with and hear the patient. The patient will have a call bell so that he or she can let the staff know if he or she has any problems during the procedure.
During the scanning process, a clicking noise will sound as the magnetic field is created and pulses of radio waves are sent from the scanner. The patient may be given headphones to wear to help block out the noises from the MRI scanner and hear any messages or instructions from the technologist.
It is important that the patient remain very still during the examination.
At intervals, the patient may be instructed to hold his or her breath, or to not breathe, for a few seconds, depending on the body part being examined. The patient will then be told when he or she can breathe. The patient should not have to hold his or her breath for longer than a few seconds, so this should not be uncomfortable.
Magnetic resonance imaging uses magnets and radio waves to take pictures inside the body.
Virtual colonoscopy is a procedure that is done to look for small polyps or other growths inside your colon. Polyps that grow on the inside lining of the colon sometimes turn into colon cancers. The American Cancer Society recommends that men and women begin screening for colon cancer at age 50. If you have a family history of colon cancer or are at high risk for other reasons, your health care provider may want you to begin screening even earlier. Virtual colonoscopy every five years is one of several screening options.
Virtual colonoscopy is done by taking hundreds of cross-sectional X-rays of the colon using a powerful type of computer. The computer can put all the images together to form the whole picture. These images can then be viewed by X-ray specialists and your doctors. This type of imaging is called computed tomography (CT), and the machine that makes them is called a CT scanner. The images can also be copied, transferred, and printed.
Colon cancer is the third most common cancer in men and women. The reason for virtual colonoscopy is to find colon cancer at an early stage when it can be treated most successfully. Colon polyps that are found by virtual colonoscopy can be removed (using conventional colonoscopy) before they turn into cancer.
An older and still common type of colonoscopy, called conventional colonoscopy, is also done to screen for colon cancer. This procedure is done by placing a long, flexible, lighted scope and tiny camera into the colon so that the doctor can look at the colon directly and remove any polyps that are present.
Virtual colonoscopy has several advantages over conventional colonoscopy:
Virtual colonoscopy is less uncomfortable and invasive than conventional colonoscopy and usually does not require any pain medication or anesthesia.
Virtual colonoscopy takes less time and poses less risk of puncturing the large intestine.
Virtual colonoscopy may be used in people who have problems such as swelling, bleeding, or breathing difficulties and who may not be able to tolerate conventional colonoscopy.
Virtual colonoscopy may be able to show areas of the large intestine that conventional colonoscopy can't reach.
Virtual colonoscopy is a safe procedure, but it's not without risk. Conventional colonoscopy, however, also has some drawbacks. Among the risks and disadvantages of virtual colonoscopy:
During virtual colonoscopy, a small, short tube is placed into your anus so that air can be pumped into your colon. This inflates your colon so that polyps or other growths are more easily seen. Pumping air into the colon carries a very small risk that it may cause a rupture. But the risk is thought to be much less than with conventional colonoscopy.
Because polyps or suspicious growths cannot be removed or biopsied during virtual colonoscopy, you may still need to have a conventional colonoscopy if polyps or other suspicious areas are detected.
Virtual colonoscopy can miss some polyps that may turn into cancer if they are smaller than 10 mm. (Some of these might be detectable by conventional colonoscopy.)
Unlike most other screening tests, virtual colonoscopy uses X-rays to create pictures of the colon and rectum. Radiation received during virtual colonoscopy is small, but it could be dangerous for pregnant women. If you are or could be pregnant, you should discuss this risk with your health care provider before the procedure.
Virtual colonoscopy is still fairly new, and it may not always be covered by medical insurance.
There may be other risks, depending on your specific medical condition. Be sure to discuss any concerns with your health care provider before the procedure.
Before having a virtual (or a conventional) colonoscopy, you will need to have a bowel prep. A bowel prep is a way of emptying everything solid from your colon so that the CT images will be clear. Here is what is often involved with a bowel prep:
Your health care provider may ask you to limit your diet to clear liquids such as water, Gatorade, or clear broth for a day or two before the procedure.
The day before the procedure, you will be given a strong laxative in pill form or powder dissolved in liquid to help you empty your colon. You will likely have several loose or liquid bowel movements in the following hours.
Just before the procedure you may be given a type of liquid to drink called contrast media that helps the inside of your colon appear brighter for the X-rays.
Always tell your health care provider about any medications you are taking and if you've had any reactions to contrast media for other X-rays in the past.
Virtual colonoscopy can be done wherever a CT scanner is available. In most cases you will go to the radiology department of a hospital or medical center. The actual procedure takes only about 10 to 15 minutes. This is what usually happens during a virtual colonoscopy:
The thin tube will be placed into your rectum to inflate your colon with air. You may feel a slight fullness.
A radiologist will position you face up on a table that slides into the CT scanner.
The radiologist will leave the room and the CT scanner will be operated from a separate control room. You will be able to hear and talk with the staff.
The table will move into and through the scanner. You may hear some whirring and clicking noises.
You may be asked to hold your breath at times.
The scan may need to be repeated while you lie face down.
In most cases you should be able to return home without assistance and resume your normal diet and activities. Medications and special instructions are usually not needed, but always check with your health care provider and the radiology staff if you have any questions.
Less invasive than a traditional colonoscopy, VCs combine software with MRIs or CT Scans.
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