What is CT scan or CAT scan?
A CT or CAT scan is a diagnostic imaging technique which uses a combination of X-rays and computer technology to produce horizontal, or axial, images of the body (often called slices). A CT scan provides clear photographs of every body part, including the bones, muscles, fat, lungs, and blood vessels. More comprehensive CT scans than normal X-Ray scans. In normal X-rays, the body part being examined is exposed to a beam of energy. A plate behind the portion of the body catches energy beam variations as it passes through skin, bone, muscle and other tissue. While much knowledge can be obtained from a standard X-ray, there is not much data available on internal organs and other structures. The X-Ray beam travels across the body in a circle, in computed tomography. This facilitates many different views of the same organ or structure, and offers much more detail. The X-Ray information is sent to a computer which interprets and displays the X-Ray data on a monitor in two-dimensional form. New technology and computer software allow for three-dimensional ( 3-D) images.
CT scans may be performed with contrast or without. “Contrast” refers to a drug that is taken by mouth or inserted into an intravenous ( IV) line, which makes the actual organ or tissue under examination more clearly visible. Contrast exams can require that you speed for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure. CT scans can help diagnose tumours, investigate internal bleeding or search for other internal injuries or injury.
You may want to ask your doctor about the amount of radiation used during the CT procedure as well as the risks associated with your case. It is a good idea to keep track of your prior records of exposure to radiation, such as previous CT scans and other forms of X-rays, so you can educate your doctor. Risks associated with radiation exposure can be linked over a long period of time to the total number of X-Ray exams and/or treatments. If you are pregnant or think you might be pregnant, tell your doctor.
Advances in computed tomography technology include the following:
- High-resolution computed tomography: This form of CT scan uses very thin slices (less than one-tenth of an inch), which in some cases, such as lung disease, are useful in offering more detail.
- Helical or spiral computed tomography: Both the patient and the X-Ray beam constantly shift during this form of CT scan, with the X-Ray beam rotating around the patient. The images are collected much quicker than with normal CT scans. The resulting images have higher resolution and contrast and thus provide more accurate information. Multidetector row helical CT scanners can be used to provide details on Calcium build-up inside the heart’s coronary arteries.
- Ultrafast computed tomography (also called electron beam computed tomography): This type of CT scan creates images very quickly, thereby producing a form of “movie” of moving body parts, such as the heart chambers and valves. This scan can also be used to obtain Calcium build-up information within the heart’s coronary arteries, but the helical scanners are far more popular.
- Computed tomographic angiography (CTA): Angiography (or arteriography) is an image of the blood vessels by X-Ray. A CT angiogram uses CT technology to acquire images of blood vessels, for example, the heart’s coronary arteries, rather than traditional X-rays or Fluoroscopy.
- Combined tomography measured with positron emission tomography ( PET / CT): PET / CT is the integration of computed tomography and positron emission tomography technologies into one integrated unit. PET / CT combines CT’s ability to provide comprehensive anatomy with PET’s ability to demonstrate cell function and metabolism to provide greater precision in the diagnosis and treatment of some forms of diseases, especially cancer. PET / CT can also be used to determine epilepsy, Alzheimer’s and coronary artery disease.
Studies suggest that 85 percent of the population will not experience an iodinated contrast adverse reaction; however, if you have ever had a reaction to any contrast dye and/or kidney problems, you will need to let your doctor know. A reported allergy to seafood is not considered a contraindication to the iodinated comparison. If you have any medical problems or recent illnesses, notify your doctor. Over the past decade, the effects of kidney disease and contrast agents have gained greater interest, as patients with kidney disease are more vulnerable to kidney damage following exposure to contrast.
You should contact your health care provider if you are pregnant, or think you might be pregnant. If you are claustrophobic or appear to get nervous quickly, inform your doctor ahead of time, as he or she can prescribe a mild sedative to make you more relaxed before the operation. During the operation, which can take 10 to 20 minutes, you will need to stay still and quiet.
How is a CT or CAT scan performed?
CT scans may be done on an outpatient basis unless they are part of inpatient treatment for a patient. Whilst each facility can have unique protocols in place, CT scans typically follow this method:
- Upon arrival for the CT scan, the patient may be asked to remove any clothes, jewelry or other items that could interfere with the scan. If the patient is taking a contrast treatment, an intravenous ( IV) line may be initiated in the hand or arm for the contrast drug to be administered. The patient shall be given the contrast substance to swallow for oral comparison.
- The patient will lie on a scan table, which slides into the scanning machine’s wide, circular opening.
- The CT team will be in another room where the controls to the scanner are mounted. The patient would also be through a window in constant sight of the workers. Speakers inside the scanner enable the staff to communicate with the patient and listen to him. The patient will have a call bell to let the staff know if he or she is having any difficulties during the process.
- As the scanner rotates around the patient, X-rays can continue for a brief period of time travel through the body. The motion is concealed within the gantry, the machine’s doughnut-shaped portion.
- As the X-Ray tube rotates, the patient can hear ringing, whirling and clicking.
- The scanner will identify the X-rays absorbed by the body’s tissues and pass them on to the device.
- The computer will convert the information into a picture which the radiologist can interpret.
- During the process, it is very important for the patient to stay very still. During the procedure, you may be asked to hold your breath at different times.
- The technologist will always observe the patient and will be in continuous contact.
- The patient may be asked to wait a short time while the radiologist looks at the scans to make sure they are clear. If the scans are not sufficiently clear to obtain adequate details, additional scans will need to be performed.