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 or if a relapse has occurred. For an MRI, the patient lies on a table that is rolled into a machine. The machine surrounds them on all sides, like a tube. The MRI is painless, but the machine makes loud noises. Your child may use ear plugs or a headset during the MRI. They must be able to lie completely still, and some children require sedation to do this. The MRI usually takes 1–2 hours. Often, a dye is injected into a vein to improve the MRI images. Because they use strong magnets, MRI machines cannot have metal objects inside them. Before an MRI, your child will be asked to remove all metal objects such as jewelry and clothes with metal snaps or zippers. An MRI does not expose your child to any form of radiation. CT SCAN A CT (computerized or 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 useful 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 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, and 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 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 it may be able to detect relapse before an MRI or CT can. A glucose solution (a type of sugar solution) that contains a slightly radioactive substance is given through the child’s 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
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