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What is Magnetic Resonance Imaging (MRI)?
Magnetic Resonance Imaging is technology that allows your physician to see inside your body without surgery or potentially harmful ionizing radiation. MRI "sees through" bone and can image soft tissue in any part of the body. The pictures produced assist your doctor in diagnosing health problems at their earliest, most treatable stages. In many cases, MRI eliminates the need for additional diagnostic procedures.

An open MRI is specifically designed for claustrophobic patients and patients who are not comfortable in traditional MRI scanners. Patients of most any size maybe scanned in an open scanner. Other patients can be scanned in a more powerful standard "high-field" MRI scanner available at several locations. Your physician can help you decide which technology best suits your situation.

How does it work?
MRI uses two forces: Magnetism and Radiowaves.

You are placed inside a strong magnetic field for your examination. This causes the hydrogen atoms in your body to align themselves in a position to receive radio signals. Your body responds and transmits signals of its own that are processed by a computer and made into images or pictures.

Q. Is MRI harmful?
A. No. MRI uses no X-rays or other ionizing radiation and no known harmful side effects have been discovered to date

Q. How long does an MRI scan take to perform?
A. Because MRI scans allow us to obtain images in multiple planes they take from 45 minutes to 90 minutes to complete and consist of 4 to 6 different individual scans, often providing 50 to 100 different pictures.

Q. How does MRI work?
A. MRI stands for Magnetic Resonance Imaging. It is a very complex process that uses strong stable external magnets, variable magnetic gradients, strong radio frequency waves, very sensitive radio receivers, and powerful computers. These magnets and gradients cause fluctuations in the water protons in the body, which are tiny magnets. The resulting pictures of slices throughout the body parts are representations of the concentration and other properties of water in the body. These pictures give detailed views of the anatomy and diseased tissue located in the body

What is Computed Axial Tomography (CT Scan)?

Q. How is a CT Scan different from an MRI?
A. CT (or CAT) stands for Computed Axial Tomography. This technique of imaging uses an X-ray tube that rotates in a large circle around the subject and the X-rays that pass through the body slice are detected by a large number of detectors located around the same circle. A powerful computer analyzes the resulting information and a picture is provided of slices representing the relative X-ray densities of the slice being imaged.

Q. Is CT Scanning dangerous?
A. The CT Scanner uses X-rays, which do have some potential side effects in large or prolonged doses. The X-ray dosage for the usual CT scan is minimal to the subject. Because of the risk of radiation-induced birth defects, it is not usually advisable to perform CT scanning if the subject is pregnant, particularly in the early stages.

Q. How long does a CT Scan take?
A. The usual CT Scan takes about 45 minutes to perform and like the MRI, the subject must remain perfectly still. For this reason we perform general anesthesia for the exam just as we do for MRI.

Q. What is CT useful for diagnosing?
A. CT is very useful in diagnosing disorders of the skeletal system, chest, abdomen, brain, and sinuses. CT is much clearer in imaging problems with bone and calcifications, which MRI does not pick up at all.

Q. What if a dye injection is necessary?
A. It is often necessary to perform a CT scan after the intravenous injection of an iodine containing dye. This substance is dense to X-ray and allows us to see normal and abnormal vascular structures that might otherwise go undetected. The dyes used relatively safe although serious allergic reactions can rarely occur. These dyes contain Iodine and are eliminated by the kidneys, thus they cannot be used in animals with severe kidney problems.

What is Ultrasound (U/S)?

Q. What is Ultrasound and how does it work?
A. Ultrasound is a technique of imaging soft tissues by using a probe with a crystal that can send out a high frequency pulse of sound and can also receive any reflected sounds and record them, making a sort of map of the object that is reflecting the sound. Modern day ultrasound equipment uses probes that have hundreds of crystals arranged in a row that can take a live real-time picture(s) of a slice of the body.

Q. Is Ultrasound harmful?
A. There are no known side effects of the type of ultrasound used in clinical imaging.

Q. What is Ultrasound good for?
A. Ultrasound is very useful in evaluating soft tissue structures in the abdomen and pelvis, in looking at the heart, and in evaluating tendons. Because Ultrasound does not cause damage, it is particularly useful in evaluating reproductive problems, and even in trying to count the number of fetuses present. It is also very useful in looking at cysts and tumors and in evaluating heart disease.

What is PET (Positron Emission Tomography)?

Q. What is PET?
A. Positron emission tomography, also called PET or a PET scan, is a diagnostic examination that involves the development of biologic images based on the detection of subatomic particles. These particles are emitted from a radioactive substance given to the patient. The subsequent views of the human body are used to evaluate function.

Q. What are some common uses of the procedure?
A. Specifically, PET scans are used to detect cancer and to examine the effects of cancer therapy by characterizing biochemical changes with the cancer. These scans are performed on the whole body. PET scans of the heart can be used to determine blood flow to the heart muscle and help evalauate signs of coronary artery disease. Combined with a myocardial metablolism study, PET scans differentiate non-functioning heart muscle from heart muscle that would benefit from a procedure, such as angioplasty or coronary artery bypass surgery, which would re-establish adequate blood flow. PET scans of the brain are used to evaluate patients who have memory disorders of an undetermined cause; who have suspected or proved brain tumors; or who have seizure disorders that are not responsive to therapy, therefore, are candidates for surgery.

Q. How does the procedure work?
A. Before the examination begins, a radioactive substance is produced in a machine called a cyclotron and attached, or tagged, to a natural body compound, most commonly glucose, but sometimes water or ammonia. This process is called radiolabeling. Once this attached substance is administered to the patient, the radioactivity begins to breakdown in the body, resulting in the release of energy that is detected by the PET scanner.

Different colors or degrees of brightness on a PET image represent different levels of body function. For example, because healthy tissue uses glucose for energy, it accumulates some of the radiolabeled glucose, which will show up as background areas on the PET images. Cancerous tissue, which uses more glucose than normal tissue, will absorb more of the substance and appear brighter on the PET images.

Scientifically speaking, the radioactive substance delay leads to the ejection of positive electrons (called positrons and sometimes referred to as anti-matter). A positive electron travels about one to two millimeters before colliding with an electron. The collision results in a conversion from mass to energy, resulting in the emission of two gamma rays heading off in exact opposite directions. Special crystals, called photomultiplier-scintellator detectors, within the PET scanner detect the gamma rays being omitted, and a connected computer uses the information and the complicated mathematical formulas, called alogrithms, to map an image of the area where the radioactive substance has accumulated.

Q. How is the procedure performed?
A. A nurse or technologist will take you into a special PET examination room. You will lie down on an examination table and be given the radioactive substance as an intravenous injection (although, in some cases it will be given through an intravenous line or inhaled as a gas). It will then take qpproximately 30-60 minutes for the substance to travel through your body and be absorbed by the tissue under study. After that time, scanning begins. This takes an additional 30-45 minutes.

Some patients, specifically those with heart disease, may undergo a stress test in which PET scans are obtained while they are at rest, then after undergoing the administration of the pharmaceutical, to alter the blood flow to the heart.

Usually, there are no restrictions on daily routine after the test, although you should drink plenty of fluids to flush the radioactive substance from your body.

Q. What are the benefits versus risks?
A. Because PET allows study of body function, it can help physicians detect alteration in biochemical processes that suggest disease before changes in anatomy are apparent.

Because the radioactivity is very short-lived, your radiation exposure is extremely low. The substance amount is so small that is does not affect the normal processes of the body. If it did, the test results would be unreliable since your doctor would not be sure of whether biochemical changes in your body were the result of a disease or the presence of the radioactivity.

The radioactive substance may expose the fetus of patients who are pregnant or the infants of women who are breast-feeding to the radiation. The risk to the fetus or infant should be considered related to the information gain from the potential results of the PET examination.

Radiological Physician Associates, Inc
Radiological Physician Associates, Inc
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