MRI MRI (magnetic resonance imaging) uses radio waves and magnetic fields instead of X rays to create very detailed pictures of parts of the body. A computer translates the pattern of radio waves into images. MRI images are so clear that they are sometimes more useful than X rays or CT scans. This is true for areas of the brain and spinal cord, blood vessels, bones, and some organs of the body. Certain tumors are regularly checked by MRI during and after treatment to determine how effective the treatment is and if a relapse has occurred. CT SCAN A CT (computed tomography) scan is a computer-assisted X ray that creates detailed pictures of internal organs and tumors. It used to be called a CAT (computerized axial tomography) scan. The CT machine is a doughnut- shaped X-ray camera that moves around a table that the patient lies on. Every second, the camera moves a very small distance around the patient while taking an X ray. A computer puts these X rays together to help the doctors see a cross-sectional 3-D image from all angles. CT scans are very helpful in diagnosing and following the stage and location of cancer. CT scans are very useful in diagnosing tumors, infections, blood clots, and areas of abnormal bleeding. Some tumors are regularly checked by CT scan during and after treatment to see how effective the treatment has been and if a relapse has occurred. CT scans are painless, but the patient must lie still during the scan. Some children require sedation to help them lie still. If your child’s belly is being scanned, they may be asked to drink a dye that allows organs to be seen more clearly. Some patients may be given a small amount of dye through an intravenous (IV) line, which puts the dye right into their veins. The dye can cause a warm, flushing feeling. Generally, there are no side effects from either type of dye; however, allergic reactions are possible. Because there is some radiation exposure with this test, your child’s healthcare team will try to minimize how often it is done. BONE SCAN A bone scan is used to look for abnormalities in bones. It can be helpful in diagnosing primary bone tumors, cancers that have spread to bones, or infections in the bone. A small amount of radioactive dye (isotope) is given through an IV line and travels around the body. This isotope is picked up by tumor cells, which allows for the tumor’s location in the body to be seen. Pictures are taken about 2–3 hours after the injection. The test is painless, but some children require sedation to lie still for the scan. The radioactive isotope leaves the body in the urine over 2–3 days. There is very little radiation exposure from a bone scan. PET SCAN A PET (positron emission tomography) scan can tell the medical team a lot about how cells of the body are working. It shows the chemical and functional changes within the body. Because functional changes take place before physical changes, PET scans can help diagnose cancer early. A PET scan is very helpful in diagnosing specific cancers, especially lymphomas and some solid tumors. In addition, often it can determine if enlarged lymph nodes contain cancer cells and can provide information about the stage or extent of the cancer. A PET scan is also helpful when determining the effectiveness of treatment or if a relapse has occurred and may be able to detect relapse before an MRI or CT can. For the PET scan, a glucose solution (a type of sugar solution) that contains a slightly radioactive substance is given through an IV line. The child must wait, usually 30–60 minutes, for the solution to travel throughout the body. Certain cells absorb the glucose solution more than others, and they light up in pictures taken during the PET scan. The body eventually gets rid of the glucose solution naturally, and no special precautions are needed. The PET scanner is a doughnut-shaped camera (very similar to a CT scanner) with a table that the patient lies on. The patient will move through the doughnut-shaped camera, while lying on the table, a few different times during the scan. A PET scan is painless but may take a while. The child must be able to lie still; some children may require sedation. Some food and medications may interfere with PET scan results, so your child will be given special diet instructions before the day of the scan.
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