CT scan

CT plain scan, also known as normal scan, refers to the scanning of iodine-free contrast agents in the vein. It is usually used for primary CT examination. The most important thing for CT scan is to grasp the layer thickness and layer of different parts or organs and regions of interest. Distance technology, when the layer thickness is equal to the layer distance, it is continuous scanning, there is no gap between adjacent layers. When the layer thickness is less than the layer spacing, there is a gap between the two adjacent layers. The choice of layer thickness depends on the site or organ being examined and the size of the lesion. Usually larger organs are 1cm thick, such as brain, chest, abdomen, etc.; nasopharynx, neck, pancreas, prostate, etc. usually use 0.5cm layer thickness; eyes, throat, adrenal gland usually use 0.2~0.3cm layer thickness; brain The pituitary body is layer thickness <= 0.2 cm. If a small lesion, that is, an area of ​​interest, is found in a large organ, a 0.2-0.3 cm layer thickness scan should be performed on the area to accurately display the size and density of the lesion to overcome the effect of partial volume effect. If the layer thickness is large, the CT value obtained for the substance containing two or more different densities in the same layer cannot accurately reflect the CT value of any of the substances. If the lesion tissue is denser than the surrounding tissue, and the lesion thickness is smaller than the layer thickness, the measured CT value is smaller than the actual one. On the contrary, its CT value is higher than the actual CT value. Due to the influence of partial volume effect, if the edge contour of different structural objects in the layer is slanted, the contour is unclear due to the inaccuracy of the CT value, such as the lateral ventricle top, the dome, and the upper and lower poles of the kidney. Basic Information Specialist classification: growth and development check classification: CT Applicable gender: whether men and women apply fasting: not fasting Tips: Patients who have a CT scan of the abdomen should take an appropriate amount of water containing contrast medium before the test. Normal value There was no abnormality in the CT examination image. Clinical significance Abnormal results CT examination image is clear, density resolution is high, it is 10 to 20 times higher than ordinary X-ray examination, head examination can show the gray matter and white matter of brain tissue, ventricular system and subarachnoid space, can directly display brain tumor, Cerebral hemorrhage, cerebral infarction and other changes; lung examination can clearly show the fine texture of the lung; can clearly show the liver, spleen, pancreas, kidney, adrenal gland and other organs, contours and lesions, which are not displayed by ordinary X-ray examination. CT examination can provide a true cross-sectional image. These images have no overlapping images of different organ lesions, which can interfere with observation and provide details of organs and lesions on the examined surface, so that the positioning accuracy reaches a high level. Patients with brain tumors, cerebral hemorrhage, and cerebral infarction who need to be examined. Precautions Taboo before inspection: 1. Patients who have a CT scan of the abdomen should take an appropriate amount of water containing contrast medium before the examination. Patients who have a pelvic CT scan should take a large amount of water or a contrast medium. After the bladder is full, CT scan is performed. . 2. Patients undergoing CT examination should remove metal objects from the inspection area to reduce artifacts. Requirements for inspection: Actively cooperate with doctors. Inspection process Before the abdominal or pelvic examination, the oral positive contrast agent makes the intestinal tract non-transparent, which should be used as a routine preparation before CT examination, but the technique is not an enhanced scan. Its main purpose is to use the contrast agent to mark the gastrointestinal cavity. To clear the boundaries between the gastrointestinal and solid organs, and to make the boundaries between normal gastrointestinal organs and diseased tissues or organs clear. The concentration of the oral contrast agent is 1.3% to 3.5% of the parental glucamine or 1% to 3% of the diatrizoate. Preparation for non-transparentization of the upper abdomen: 250~500ml of contrast agent after oral dilution, repeated in 15~30min before scanning until the start of scanning. CT scan of the whole abdomen should be non-transparent in the whole abdomen. It is best to combine oral and enema methods. The effect is ideal. In the afternoon before the patient examination, 800~1000ml diluted iodine water should be refilled and cleaned the next morning. After enema, the enema is diluted with 150 ml of iodine water, and then diluted with iodine water 250~500 ml 15 to 30 minutes before scanning, so that the whole digestive tract can be prepared to achieve ideal non-permeation preparation. The non-transparent preparation of the abdominal plain scan is also applicable to abdominal augmentation scans. There is no need to force a patient for failure. Those with known heart failure should be banned from a large number of hypotonic solutions to avoid increasing cardiac load. CT is suitable for the detection of new organisms in various parts of the body, the location diagnosis of a small number of tumors, the extent of tumor distribution, infiltration and metastasis, and CT-guided biopsy; suitable for the detection of inflammation in most parts of the body and the determination of its size. Such as brain, sputum, sinus, mediastinum, liver (inflammation or abscess such as bacteria or protozoa) inflammation of the pancreas and bones; for the detection of major vascular lesions (vascular malformations, hemangioma, vascular occlusion, bleeding) And qualitative diagnosis; has important value for determining the quantitative and qualitative bleeding of important organ trauma, is also very valuable for the location of a variety of traumatic foreign bodies, and is very sensitive to the detection of calcification or stones in some areas. CT is also suitable for the detection of a degeneration or congenital anomaly, such as liver steatosis and congenital abnormalities of the central nervous system. Not suitable for the crowd Inappropriate people: patients with allergies to iodine and heart failure.

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