Computed Tomography Scanning or CT Scan

A CT scanner is an X-ray machine with a difference. Instead of sending one X-ray beam through your body, the scanner sends a succession of very narrow beams at different angles. An array of detectors picks up the beams which are weakened by differing amounts by the tissues they pass through and sends signals to a computer. From the information pro- vided, the computer can reconstruct a two dimensional slice through the body, which is displayed on a TV screen.

CT images are more detailed than those produced by X-rays alone and can be manipulated using a computer so that tissues can be seen from different angles or even in three dimensions. In addition, CT scanning minimizes the amount of radiation exposure to the patient.

Preparing for the procedure

Before some CT scans, you may be given an injection of contrast medium containing iodine that will clearly show certain blood vessels, organs, or abnormalities such as tumors. The IV enhancing agent may give you a brief sensation that moves up your arm. You also may get a warm, flushed feeling; a taste of salt or metal in your mouth; or nausea for a few minutes. This is normal, but you should tell the technologist about these or other reactions. You may also experience nausea, shortness of breath, itchiness, or sneezing. If any of these occur, tell the doctor or technologist right away.

During the scan, you lie on a table with the part of your body to be examined within the circular opening of the scanner. You will not feel any sensation as the X-rays pass through you. Soon an image, viewed by the radiologist, appears on the screen attached to the console of the instrument.

You may feel the table on which you are laying move a little every few seconds as each image is obtained. The amount of time it takes to complete the examination will depend on how many exposures are made during each slice and on the number of angles required. It may also take the technician a little time to position you correctly and set up the machine.

CT scans can detect hundreds of levels, bringing out details, especially of soft tissues, that are impossible to see with conventional X-rays. Body tissues that have differing densities, such as bone, fat, and muscle, are clearly delineated on the image produced by a CT scan. The findings of CT scans are highly accurate in most cases.

Chest Computed Tomography Scan or Chest CT Scan

Chest CTs are very useful for evaluating various abnormalities. In general, the test can be particularly helpful in evaluating conditions like aortic aneurysm, aortic dissection, and fluid around the heart.

Coronary CT Angiography

CT coronary angiography (CTA) is a very fast imaging technology, that takes multiple X-ray cross-sections of the heart (like slices of bread). The whole heart can be imaged in approximately five heart beats. A computer then assembles the cross sectional images into a detailed picture of the heart. It is "non-invasive" because the body is not physically entered except for a cannula in the arm used to give contrast dye. This contrast dye fills the arteries and the heart chambers briefly making them visible on X-ray pictures. The arteries that take blood to the heart muscle are called coronary arteries and the CT pictures give information about narrowings, fat deposits and calcium in the arteries. In addition, CTA gives information about heart muscle function, valves, and the pericardial sac that encloses the heart. The cardiologist is provided with extensive information that helps determine patient management and thus may prevent heart attacks and cardiovascular death.

What will happen During CT Angiography?

A small intravenous cannula will be inserted into a vein in your arm, before you go to the CT Room. You will lie on the table. Medication may be given into the vein to slow your heart rate. You will usually be given nitroglycerin spray under the tongue to dilate your coronary arteries during the scan. This may on occasion cause a slight headache. Contrast dye will be injected through a vein in your arm. You will be instructed to hold your breath. You will experience a brief warm flush, which spreads throughout your body. This is a normal reaction to the contrast dye. You will be on the table for only a few minutes while it moves through the CT "doughnut" and the images are being taken by the X-ray machine.

The computer generates 3D images from the 2D slices taken. A technologist, cardiologist and radiologist will be involved in reviewing your images. A full report of the CT Angiography will be made by a Cardiologist and sent to your referring Cardiologist or Specialist