CT Scanning – Techniques and Applications
Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The original systems were dedicated to head imaging only, but “whole body” systems with larger patient openings became available in the late 1970’s. Technical advancements in developing high-power x-ray tubes and computing technologies led to two major evolutionary leaps in CT imaging during the past decade. The first of these occurred in the early 1990’s with the introduction of CT scanners with simultaneous patient translation and data acquisition (“spiral” or “helical”). The second leap occurred mid-decade, with the introduction of multiple row detectors capable of multiple slices per x-ray tube rotation. These advances improved volume coverage and/or longitudinal spatial resolution, and creating new applications that could not have been attempted before, such as CT angiography, virtual endoscopy, CT-guided surgery/radiation therapy, and computer integrated surgery. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. Each of us has written different part of this book, obviously depending on our areas of expertise. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society.CT Scanning – Techniques and Applications (PDF Download Available). Available from:
Because children are more sensitive to radiation, they should have a CT exam only if it is essential for making a diagnosis and should not have repeated CT exams unless absolutely necessary. CT scans in children should always be done with low-dose technique.
What are the limitations of CT Scanning of the Body?
Soft-tissue details in areas such as the brain, internal pelvic organs, and joints (such as knees and shoulders) can often be better evaluated with magnetic resonance imaging (MRI). In pregnant women, while CT can be performed safely, other imaging exams not involving radiation, such as ultrasound or MRI, are preferred but only if they are likely to be as good as CT in diagnosing your condition.
A person who is very large may not fit into the opening of a conventional CT scanner or may be over the weight limit—usually 450 pounds—for the moving table.
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What are the benefits vs. risks?
Benefits
CT scanning is painless, noninvasive and accurate.
A major advantage of CT is its ability 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 should have no immediate side effects.
Risks
There is no conclusive evidence that radiation at small amounts delivered by a CT scan causes cancer. Large population studies have shown a slight increase in cancer from much larger amounts of radiation, such as from radiation therapy. Thus, there is always concern that this risk may also apply to the lower amounts of radiation delivered by a CT exam. When a CT scan is recommended by your doctor, the expected benefit of this test outweighs the potential risk from radiation. You are encouraged to discuss the risks versus the benefits of your CT scan with your doctor or radiologist, and to explore whether alternative imaging tests may be available to diagnose your condition.
The effective radiation dose for this procedure varies. See the Safety page for more information about radiation dose.
Women should always inform their physician and x-ray or CT technologist if there is any possibility that they are pregnant. See the Safety page for more information about pregnancy and x-rays.
CT scanning is, in general, not recommended for pregnant women unless medically necessary because of potential risk to the fetus in the womb.
Manufacturers of intravenous contrast indicate mothers should not breastfeed their babies for 24-48 hours after contrast medium is given. However, both the American College of Radiology (ACR) and the European Society of Urogenital Radiology note that the available data suggest that it is safe to continue breastfeeding after receiving intravenous contrast. For further information please consult the ACR Manual on Contrast Media and its references.
The risk of serious allergic reaction to contrast materials that contain iodine is extremely rare, and radiology departments are well-equipped to deal with them.
one of the fastest and most accurate tools for examining the chest, abdomen and pelvis because it provides detailed, cross-sectional views of all types of tissue. used to examine patients with injuries from trauma such as a motor vehicle accident. performed on patients with acute symptoms such as chest or abdominal pain or difficulty breathing. often the best method for detecting many different cancers, such as lymphoma and cancers of the lung, liver, kidney, ovary and pancreas since the image allows a physician to confirm the presence of a tumor, measure its size, identify its precise location and determine the extent of its involvement with other nearby tissue.
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 aortic aneurysms.
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.
In pediatric patients, CT imaging is often used to evaluate:
lymphoma neuroblastoma kidney tumors congenital malformations of the heart, kidneys and blood vessels cystic fibrosis complications of acute appendicitis complications of pneumonia inflammatory bowel disease severe injuries
Radiologists and radiation oncologists often use the CT examination to:
quickly identify injuries to the lungs, heart and vessels, liver, spleen, kidneys, bowel or other internal organs in cases of trauma.
guide biopsies and other procedures such as abscess drainages and minimally invasive tumor treatments. plan for and assess the results of surgery, such as organ transplants or gastric bypass.
stage, plan and properly administer radiation treatments for tumors as well as monitor response to chemotherapy. 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. Women will be asked to remove bras containing metal underwire. You may be asked to remove any piercings, if possible.
You will be asked not to eat or drink anything for a few hours beforehand, if contrast material will be used in your exam. You should inform your physician of all medications you are taking and if you have any allergies. If you have a known allergy to contrast material, or "dye," your doctor may prescribe
Computed Tomography (CT) - Body
Computed tomography (CT) of the body uses special x-ray equipment to help detect a variety of diseases and conditions. CT scanning is fast, painless, noninvasive and accurate. In emergency cases, it can reveal internal injuries and bleeding quickly enough to help save lives.
Tell your doctor if there’s a possibility you are pregnant and discuss any recent illnesses, medical conditions, medications you’re taking, and allergies. You will be instructed not to eat or drink anything for a few hours beforehand. If you have a known allergy to contrast material, your doctor may prescribe medications to reduce the risk of an allergic reaction. These medications must be taken 12 hours prior to your exam. Leave jewelry at home and wear loose, comfortable clothing. You may be asked to wear a gown.
What is CT Scanning of the Body?
Computed tomography, more commonly known as a CT or CAT scan, is a diagnostic medical test that, like traditional x-rays, produces multiple images or pictures of the inside of the body.
The cross-sectional images generated during a CT scan can be reformatted in multiple planes, and can even generate three-dimensional images. These images can be viewed on a computer monitor, printed on film or transferred to a CD or DVD.
CT images of internal organs, bones, soft tissue and blood vessels provide greater detail than traditional x-rays, particularly of soft tissues and blood vessels.
Using specialized equipment and expertise to create and interpret CT scans of the body, radiologists can more easily diagnose problems such as cancer, cardiovascular disease, infectious disease, appendicitis, trauma and musculoskeletal disorders.
What are some common uses of the procedure?
CT imaging is:
