Computed Tomography PDF

12/2/24 Computed Tomography Bryan John Magoling, PhD Batangas State University TNEU 1 } Computed : use of computer } Tomography: Greek word tomos means "slice", graphy means "write". l Computed Tomography is the process of generat...

12/2/24 Computed Tomography Bryan John Magoling, PhD Batangas State University TNEU 1 } Computed : use of computer } Tomography: Greek word tomos means "slice", graphy means "write". l Computed Tomography is the process of generating a two-dimensional image of a slice or section through a 3-dimensional object (a tomogram) } Computed tomography (or computerized axial tomography) is an examination that uses X-ray and computer to obtain a cross-sectional image of the human body. 3 1  12/2/24 } The first commercially CT scanner was invented by Sir Godfrey Hounsfield in Hayes, United Kingdom, at EMI Central Research Laboratories using X-rays } The first EMI-Scanner was installed in Atkinson Morley Hospital in Wimbledon, England } The first patient brain-scan was done on 1 October 1971. } Emi scanner is limited to scanning only brain. 4 5 2  12/2/24 } Hounsfield and Cormack got the 1979 Nobel Prize for their contributions to CT. } Allan McLeod Cormack 's theoretical calculations on x-ray was used by Hounsfield. 6 7 3  12/2/24 8 9 4  12/2/24 } Gantry (scanner system) } Patient's table } Computer(operation control) 10 11 5  12/2/24 } Scanner system: 1. X ray tube 2. Detector system 3. Collimators 4. Filters 12 } X-ray tube: generates x-ray beams } Detector: detects the x-rays passing through the patient's body. } Collimator: narrows the beams of x-rays } Filters: these are used to filter some rays from entering the patient's body that may be harmful. 13 6  12/2/24 } 2 types } Conventional: scan is taken slice by slice and after slice the scan stops. } E.g.. from top of abdomen till the pelvis. This needs the patient to hold their breath. } Spiral scan: continuous scan taken in spiral fashion. It is quick. 14 15 7  12/2/24 16 } When X-rays pass through the human body, some of the rays are absorbed and some pass through the body to produce an image. In plain X-ray imaging, the film directly absorbs penetrated X-rays. } In CAT scanning, an electronic device called a "detector array" absorbs the penetrated X-rays, measures the X-ray amount, and transmits the data to a computer system. } A sophisticated computer system, in turn, calculates and analyzes data from each detector in each level, and finally reconstructs multiple, two-dimensional, cross-sectional images. 17 8  12/2/24 ◦ Displayed on screen ◦ Hounsfield scale( linear transformation reference being distilled water) ◦ Range from +1000(bone) to -1000(air/gas) ◦ Ct number or Hounsfield scale is a measure of radiodensity. ◦ Ct number measured in Hounsfield unit. 18 19 9  12/2/24 20 } An imaging technique of the brain that reveal tumors, blood clots, hemorrhages, or other abnormal anatomy. A series of computerized images of the brain at various levels are taken to reveal normal anatomy or any abnormality. 21 10  12/2/24 22 } Evaluate acute cranial-facial trauma } determine acute stroke } Evaluate suspected intracranial hemorrhage } Evaluate headache } Determine if there is abnormal development of the head and neck } Tumours , clots 23 11  12/2/24 lScan range starting at base of the skull; ending at vertex of the skull lRespiration: shallow breathing lPositioning lSupine lHead immobilized lArms along the sides. 24 25 12  12/2/24 26 27 13  12/2/24 } Patient preparation: } Fasting for 4 Hours before the examination. l Starting at floor of the mouth Ending at supraclavicular fossa. l Respiration suspended in expiration with no swallowing. 28 29 14  12/2/24 30 31 15  12/2/24 } Spine, airway ,carotid vessels, salivary and thyroid glands are included. To evaluate parotid or submandibular gland lesions or infections. } Head and neck diseases } Foreign bodies that are logged in the neck or upper airway } Tumours or infections of pharynx vocal cord. 32 33 16  12/2/24 } Show the size, shape, and position of lungs and other structures in the chest. } Follow up on abnormal findings from standard chest x rays. } Find the cause of lung symptoms, such as shortness of breath or chest pain. } Diagnose lung diseases such as a tumor, excess fluid around the lungs, or a pulmonary embolism. The test also is used to check for tuberculosis , emphysema and pneumonia 34 35 17  12/2/24 36 37 18  12/2/24 38 39 19  12/2/24 40 } To test abdominal pain or swelling } Masses and tumours including cancer } Injury or infections } Kidney stones } Appendicitis } Alcoholic liver diseases } Cancer of pancreas, colon, renal pelvis. } Peritoneal fibrosis 41 20  12/2/24 42 43 21  12/2/24 44 45 22  12/2/24 46 } Purpose of the Bone CT Scan } To identify abnormalities in the spine, such as spinal stenosis that may be causing back pain } To detect bone tumors and tumors in the soft tissue surrounding bones 47 23  12/2/24 } To diagnose osteoporosis, which is common in women after menopause and also may occur in men } To evaluate fracture } To detect unusual formation of bone } To diagnose joint abnormalities. 48 49 24  12/2/24 50 } Quick and painless } Can help diagnose and guide treatment for a wider range of conditions than plain X-rays } Can detect the presence of more serious problems } check if a previously treated disease has recurred } No superimposition of images. 51 25  12/2/24 } Small risk of developing cancer in future from exposure to X-rays. Risk is greater for children } Uses higher doses of radiation are used in chest , abdomen , so the risks are in general greater than other imaging types } Injection of a contrast medium (dye) can cause kidney problems or result in allergic or injection-site reactions in some people } Some procedures require anesthesia 52 } Requires breath holding which some patients cannot manage. } Ct scan of brain can affect nearby bone. } There is also risk of childhood cancer and leukaemia in mothers who have imaging during pregnancy. } Pregnant women are not allowed for this imaging. 53 26