THIS CHAPTER IS ABOUT SPIRAL CT SCAN BECAUSE CONVENTIONAL CT SCANS ARE OUTDATED TODAY
What is CT Scanning of the Body?
CT scanning-sometimes called CAT scanning-is a wonderful noninvasive radiological test that helps doctors diagnose and treat medical conditions.
CT imaging combines special sophisticated machine and computers to produce multiple images or pictures of the inside of the body. These cross-sectional images can then be examined on a computer monitor or printed.
CT scans of internal organs, bone, soft tissue and blood vessels provide great clarity and reveal more than many other investigations.
Using specialized equipment and expertise to create and interpret CT scans of the body, radiologist can more easily diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma, musculoskeletal disorders and much more.
What are some common uses of the procedure?
·It is one of the best and fastest tools for studying the head, neck, chest, abdomen, pelvis and musculoskeletal system because it provides detailed, cross-sectional views of all types of tissue.
·It is often the preferred method for diagnosing many different cancers, including lung, liver and pancreatic cancer, since the image allows a physician to confirm the presence of a tumor and measure its size, precise location and the extent of the tumor's involvement with other nearby tissue.
·It is an examination that plays a significant role in the detection, diagnosis and treatment of vascular diseases that can lead to stroke, kidney failure or even death. CT is commonly used to assess for pulmonary embolism (a blood clot in the lung vessels) as well as for abdominal aortic aneurysms (AAA).
·It is invaluable in diagnosing and treating spinal problems and injuries to the hands, feet and other skeletal structures because it can clearly show even very small bones as well as surrounding tissues such as muscle and blood vessels.
Physicians often use the CT examination to:
·quickly identify diseases and injuries of head, neck, lungs, vessels, liver, spleen, kidneys, spine ,musculoskeletal system and other internal organs
·guide biopsies and other procedures such as abscess drainages and minimally invasive tumor treatments
·plan for and assess the results of surgery
·plan and properly administer radiation treatments for tumors
·measure bone mineral density for the detection of osteoporosis
How should I prepare?
You should wear comfortable, loose-fitting clothing to your exam. You may be given a gown to wear during the procedure.
Metal objects including jewelry, eyeglasses, dentures and hairpins may affect the CT images and should be left at home or removed prior to your exam. You may also be asked to remove hearing aids and removable dental work.
You may be asked not to eat or drink anything for several hours beforehand, especially if a contrast material <http://www.radiologyinfo.org/en/glossary/glossary1.cfm?term=contrast_material>will be used in your exam. You should inform your physician of any medications you are taking and if you have any allergies.
Also inform your doctor of any recent illnesses or other medical conditions, and if you have a history of heart disease, asthma, diabetes, kidney disease or thyroid problems.
Women should always inform their physician and the CT technologist if there is any possibility that they are pregnant..
What does the equipment look like?
The CT scanner is typically a large, box like machine with a short tunnel, in the center. You will lie on a narrow examination table that slides into and out of this tunnel. Rotating around you, the tube and electronic detectors are located opposite each other in a ring, called a gantry. The computer workstation that processes the imaging information is located in a separate room, where the technologist operates the scanner and monitors your examination.
How does the procedure work?
In many ways CT scanning works very much like other x-ray examinations.
With CT scanning, x-ray beams and a set of electronic x-ray detectors rotate around you, measuring the amount of radiation being absorbed throughout your body. At the same time, the examination table is moving through the scanner, so that the x-ray beam follows a spiral path. A special computer program processes this large volume of data to create two-dimensional cross-sectional images of your body, which are then displayed on a monitor. This technique is called helical or spiral CT.
CT imaging is sometimes compared to looking into a loaf of bread by cutting the loaf into thin slices. When the image slices are reassembled by computer software, the result is a very detailed multidimensional view of the body's interior.
Modern CT scanners are so fast that they can scan through large sections of the body in very less time. Such speed is beneficial for all patients but especially children, the elderly and critically ill.
For some CT exams, a contrast material is used to enhance visibility in the area of the body being studied.
How is the CAT scan performed?
The technologist begins by positioning you on the CT examination table, usually lying flat on your back or possibly on your side or on your stomach. Straps and pillows may be used to help you maintain the correct position and to hold still during the exam.
If contrast material is used, it will be swallowed, injected through an intravenous line (IV) or administered by enema, depending on the type of examination.
Next, the table will move quickly through the scanner to determine the correct starting position for the scans. Then, the table will move slowly through the machine as the actual CT scanning is performed.
You may be asked to hold your breath during the scanning.
When the examination is completed, you will be asked to wait until the technologist verifies that the images are of high enough quality for accurate interpretation.
CT scanning of the body usually lasts between 2 and 30 minutes.
What will I experience during and after the procedure?
Most CT exams are painless, fast and easy. With helical CT, the amount of time that the patient needs to lie still is reduced.
Though the scanning itself causes no pain, there may be some discomfort from having to remain still for several minutes. If you have a hard time staying still, are claustrophobic or have chronic pain, you may find a CT exam to be stressful. The technologist or nurse, under the direction of a physician, may offer you a mild sedative to help you tolerate the CT scanning procedure.
If an intravenous contrast material is used, you will feel a slight pin prick when the needle is inserted into your vein. You may have a warm, flushed sensation during the injection of the contrast materials and a metallic taste in your mouth that lasts for a few minutes When you enter the CT scanner, special lights may be used to ensure that you are properly positioned. With modern CT scanners, you will hear only slight buzzing, clicking and whirring sounds as the CT scanner revolves around you during the imaging process.
You will be alone in the exam room during the CT scan, however, the technologist will be able to see, hear and speak with you at all times.
After a CT exam, you can return to your normal activities. If you received contrast material, you may be given special instructions.
Who interprets the results and how do I get them?
A radiologist with expertise in supervising and interpreting radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will discuss the results with you.
What are the benefits?
·CT scanning is painless, noninvasive and accurate.
·A major advantage of CT is that it is able to image bone, soft tissue and blood vessels all at the same time.
·Unlike conventional x-rays, CT scanning provides very detailed images of many types of tissue as well as the lungs, bones, and blood vessels.
·CT examinations are fast and simple; in emergency cases, they can reveal internal injuries and bleeding quickly enough to help save lives.
·CT has been shown to be a cost-effective imaging tool for a wide range of clinical problems.
·CT is less sensitive to patient movement than MRI.
·CT can be performed if you have an implanted medical device of any kind, unlike MRI.
·CT imaging provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and needle aspirations of many areas of the body, particularly the lungs, abdomen, pelvis and bones.
·A diagnosis determined by CT scanning may eliminate the need for exploratory surgery and surgical biopsy.
·No radiation remains in a patient's body after a CT examination.
·X-rays used in CT scans usually have no side effects.
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What are the limitations of CT Scanning of the Body?
Some soft-tissue details in areas such as the intervertebral discs, joints can be more readily and clearly seen with magnetic resonance imaging (MRI).
