CT (Computed Tomography, or CAT scan) of the chest uses a special X-ray machine to take detailed pictures of the organs and tissues of the chest. CT pictures are far more detailed than a standard chest X-ray. CT is useful because it can show many types of tissue (lungs, heart, bones, soft tissues, muscle, and blood vessels) at the same time.

CT scans create cross-sectional pictures (slices) of the area. The pictures are then reviewed on a computer screen.

Unlike standard X-rays, which produce pictures of the shadows cast by body structures of varying thickness, CT scanning uses X-rays in a much different way. Many X-ray beams are passed
through the chest at many angles, and special detectors measure the amount of radiation absorbed by different tissues. The X-ray tube revolves around you, and sends and records data from many angles, forming cross-sectional pictures (slices) of the area.

Modern CT units produce higher-quality pictures in a shorter time, an important feature for children and patients who are elderly or critically ill, as well as for those who cannot hold their breath for a long time. Today’s scanners can image large regions of the body, during a single 20-second breath-hold.

• Dress comfortably, but avoid any tops with a zipper, snaps or jewelry, since metal objects may affect the scan.
• Eat your regular diet until 6 hours before your scan.  Continue to drink clear liquids (water, juices, tea) until your scan.   It is important for you to continue to drink frequently before and after your scan.  Drinking water is very helpful in protecting your kidneys.  Continue to take your regular medications as prescribed by your doctor..
• Tell your doctor or the CT technologist if there is any chance you are pregnant. For certain reasons, such as checking blood vessels, you will have contrast material injected into a vein shortly before scanning begins. If this is the case, the CT technologist will ask if you have any allergies to medicines or iodine (part of many contrast materials) and if you have a history of asthma, diabetes, a heart problem, multiple myeloma, or kidney disease. These health problems may point to a greater risk of an adverse reaction to contrast material. Kidney disease makes it harder to get rid of contrast material from the bloodstream.

1. The CT technologist will place you on the CT table, using pillows to help you maintain the correct position during the scan.
2. For the first few scans, the table will move quickly through the
   scanner to check the correct starting position. The rest of the scans are made as the table moves more slowly through the hole in the scanner.
3. The best chest CT scans result when you can hold your breath. If you can’t hold your breath, you will be asked to breathe quietly and regularly.
4. If contrast material is needed for your scan, a small needle
   connected to an IV line is placed in your arm or hand vein. The contrast material will be sent through this line.
5. You will be alone during the scan, but the technologist can see and hear you, and can speak to you at any time from the control room. The exam usually takes 15 to 30 minutes, including preparation time. The actual scan time is less than 30 seconds.
6. After the CT exam is done, you may have to wait a short time while the radiologist checks the scans for quality. A few more scans may be done as needed.

• CT is painless, though you may feel some discomfort from staying still.
• If contrast injection is needed, you may feel discomfort at the
  injection site.
• You may notice a warm, flushed sensation during the injection of
  contrast material. You may also notice a metallic taste in your mouth that lasts for about 2 minutes. These reactions are normal, and go away within 1 to 2 minutes.
• Once in a while, a patient will develop itching and hives for up to
  a few hours after the injection; this can be relieved with medication. Light-headedness or shortness of breath may be due to a more severe allergic reaction – a doctor or nurse will be nearby during the exam to help you, if needed.
• Because CT uses X-rays, you may not have a family member or friend in the CT room during the exam.

A radiologist skilled in CT scanning will review and interpret the CT findings and will send a detailed report to your primary care or referring doctor, who will give you the results. The radiologist will not discuss the results with you.