Computed Tomography

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Table of Contents

X-RAYS 3-4
X-ray Risks 3
FDA's Role......................................................................................................…..4 Medical X-rays: How Much Radiation Are You Getting? 4

Overview of X-ray computed tomography 5

PROCESS of CT 14-16

CT SCAN 16-18
Applications and Clinical Benefits of CT Imaging 16
Acquisition of CT Data 18-20
CT Image Guidance of Minimally Invasive Procedures and Micro-therapy……20 RISKS and BENEFITS of CT SCANS………………………………………………..26-27 FUTURE DEVELOPMENT27-29

X-ray computed tomography (CT), introduced into clinical practice in 1972,was the first of the modern slice-imaging modalities. To reconstruct images mathematically from measured data and to display and to archive them in digital form was a novelty then and is commonplace today. CT has shown a steady upward trend with respect to technology, performance and clinical use independent of predictions and expert assessments which forecast in the 1980s that it would be completely replaced by magnetic resonance imaging. CT not only survived but exhibited a true renaissance due to the introduction of spiral scanning whichmeant the transition from slice-by-slice imaging to true volume imaging. Complemented by the introduction of array detector technology in the 1990s, CT today allows imaging of whole organs or the whole body in 5 to 20 s with sub-millimetre isotropic resolution. This review of CT will proceed in chronological order focussing on technology, image quality and clinical applications. In its final part it will also briefly allude to novel uses of CT such as dual-source CT, C-arm flat-panel-detector CT and micro-CT. At present CT possibly exhibits a higher innovation rate than ever before. In consequence the topical and most recent developments will receive the greatest attention.

X-rays are a form of electromagnetic radiation that can penetrate clothing, body tissue, and internal organs. An X-ray machine sends this radiation through the body. Some of the radiation emerges on the other side of the body, where it exposes film or is absorbed by a digital detector to create an image. And some of it is absorbed in body tissues. It is the radiation absorbed by the body that contributes to the "radiation dose" a patient gets. Because of their effectiveness in the early detection and treatment of diseases, and their ready access in doctor's offices, clinics, and hospitals, X-rays are used more today and on more people than in the past, according to the National Council on Radiation Protection and Measurements. * In the early 1980s, medical X-rays made up about 11 percent of all the radiation exposure to the U.S. population. Current estimates attribute nearly 35 percent of all radiation exposure to medical X-rays. (Nuclear medicine procedures, which use radioactive material to create images of the body, account for about 12 percent of radiation exposure, and natural sources of radiation in the environment that we're exposed to all the time make up approximately 50 percent.) * Radiation dose per person from medical X-rays has increased almost 500 percent since 1982. Nearly half of all medical X-ray exposures today come from CT equipment, and radiation doses from CT are higher than other X-ray studies. X-ray Risks

The risks of medical X-rays include:
* A small increase in the chance of developing cancer later in life. * Developing cataracts and skin burns following exposure to very high levels of radiation. The small risk of cancer depends on several factors:

* The lifetime risk of cancer increases as a person undergoes more X-ray exams and the accumulated radiation dose gets higher. * The...
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