A CT scan uses X-rays to take pictures of your insides. Modern scanners allow the scan data to be reformatted as images in other planes. For example, CT angiography avoids the invasive insertion of a catheter. Desuden kan informationen fra optagelsen bearbejdes i en computer, så de fremstår tre-dimensionelt og i flere forskellige planer. For vascular imaging, curved-plane reconstruction can be performed. CT scansÂ wouldn't normally be used to check for problems if you don't have any symptoms (known as screening). This means that a big amount of cartilage and a thin layer of compact bone can cause the same attenuation in a voxel as hyperdense cartilage alone. The voxel with the lowest attenuation is displayed. Le CT scan est d'une très grande utilité dans : La localisation des fractures du crâne ainsi que les lésions traumatiques du cerveau. The pixel itself is displayed according to the mean attenuation of the tissue(s) that it corresponds to on a scale from +3,071 (most attenuating) to −1,024 (least attenuating) on the Hounsfield scale. Surface rendering is limited in that it will display only surfaces that meet a threshold density, and will display only the surface that is closest to the imaginary viewer. What should be included: During a calcium scoring heart CT scan, which takes about 10 minutes, computerized tomography is used to detect calcification in the arteries, which can indicate a risk of heart disease. Therefore, high-attenuating structures such as blood vessels filled with contrast media are enhanced. Multiplanar reconstruction (MPR) is the creation of slices in more anatomical planes than the one (usually transverse) used for initial tomography acquisition.  CT scans may be used to diagnose headache when neuroimaging is indicated and MRI is not available, or in emergency settings when hemorrhage, stroke, or traumatic brain injury are suspected. Services in the ER cost a lot, because of fees for doctors, services, and facilities. In general, the radiation dose associated with a routine abdominal CT has a radiation dose similar to three years average background radiation.. The table reports average radiation exposures, however, there can be a wide variation in radiation doses between similar scan types, where the highest dose could be as much as 22 times higher than the lowest dose. It's thought exposure to radiationÂ during CT scans could slightly increase your chances of developingÂ cancer many years later, although this risk is thought to be very small (less than 1 in 2,000). PCDs have several potential advantages, including improving signal (and contrast) to noise ratios, reducing doses, improving spatial resolution, and through use of several energies, distinguishing multiple contrast agents. , For purposes of comparison, the world average dose rate from naturally occurring sources of background radiation is 2.4 mSv per year, equal for practical purposes in this application to 2.4 mGy per year. Most adverse health effects of radiation exposure may be grouped in two general categories: The added lifetime risk of developing cancer by a single abdominal CT of 8 mSv is estimated to be 0.05%, or 1 one in 2,000.. These scans have been optimal for research focused on the workings of the Antikythera mechanism or the text hidden inside the charred outer layers of the En-Gedi Scroll.  In the United Kingdom it accounts for 15% of radiation exposure. The term "CAT scan" is not used anymore, since CT scans nowadays allow for multiplanar reconstructions. For example, CT images of the brain are commonly viewed with a window extending from 0 HU to 80 HU. By reformatting the volume, it becomes much easier to visualise the position of one vertebral body in relation to the others. CT scanning bruges især ved mistanke om svulster, blødninger eller skader på en række organer. The benefits and risks of having a CT scan willÂ always be weighed up before it's recommended. CT scans around the abdomen are not advised for pregnant women because of a chance the fetus would be exposed to harmful radiation. ThisÂ normally takes a few days or weeks. MPR is frequently used for examining the spine. A computed tomography (CT) scan of the head is an imaging scan that uses X-rays to develop a 3D image of the skull, brain, and other related areas of the head. Water has an attenuation of 0 Hounsfield units (HU), while air is −1,000 HU, cancellous bone is typically +400 HU, and cranial bone can reach 2,000 HU or more (os temporale) and can cause artifacts. , In the United States half of CT scans are contrast CTs using intravenously injected radiocontrast agents. Taking care of yourself at home after a CT scan. , The 1979 Nobel Prize in Physiology or Medicine was awarded jointly to South African American physicist Allan M. Cormack and British electrical engineer Godfrey N. Hounsfield "for the development of computer assisted tomography. It has more recently been used for preventive medicine or screening for disease, for example CT colonography for people with a high risk of colon cancer, or full-motion heart scans for people with high risk of heart disease. , The sievert unit is used in the report of the effective dose.
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