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Computed tomography

Computed tomography. Dr Mohamed El Safwany , MD. Intended learning outcome. The student should learn at the end of this lecture procedures of CT. Computed tomography.

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Computed tomography

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  1. Computed tomography DrMohamed El Safwany , MD.

  2. Intended learning outcome The student should learn at the end of this lecture procedures of CT.

  3. Computed tomography • 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.

  4. Computed tomography • When X-rays are irradiated on 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.

  5. Computed tomography Gantry and Table Operation console

  6. Computed tomography

  7. Computed tomography Feet first Head first

  8. Computed tomography Risks • Iodine is the usual contrast dye. Some patients are allergic to iodine and may experience a reaction that may include nausea, breathing difficulty, or other symptoms. • The amount of radiation used during a CT procedure is considered minimal; therefore, the risk for radiation exposure is very low. • Radiation exposure during pregnancy may lead to birth defects.

  9. Before the Procedure • explain the procedure to the patient. • If the procedure involves the use of contrast dye, consent should be signed form the patient. • Ask the patient if he has ever had a reaction to any contrast media. • Generally, there is no fasting requirement prior to a CT scan, unless a contrast media is to be used. (abdomen and pelvis need fasting and cleaning the colon – iv contrast need fasting 4 hours before the examination).

  10. CAT scan examination • CT angiography • Dynamic CT • CT Diffusion and perfusion • High resolution technique • CT fluroscopy • Virtual real endoscopy

  11. CT Scan of the Brain • 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.

  12. Computed tomography

  13. Computed tomography • A CT scan is recommended to help: • Evaluate acute cranial-facial trauma • determine acute stroke • Evaluate suspected subarachnoid or intracranial hemorrhage • Evaluate headache • Determine if there abnormal development of the head and neck

  14. Computed tomography • Positioning • Supine • Arms along the sides of the body • Head immobilized in the head holder

  15. Parameters Computed tomography • Scan range starting at base of the skull; ending at vertex of the skull • Respiration: shallow breathing

  16. Unit controls Computed tomography • Gantry tilt: depend on examination. • Lateral scout view. • Scout view is used for planning • Gantry tilt: parallel to orbitomeatal line • Slice thickness: • 4mm to the posterior fossa (skull base to tentorial rim). • 7mm from tentorial rim to vertex.

  17. Computed tomography

  18. Soft-tissue

  19. Computed tomography Bone window

  20. Pathological findings (tumor – metastases) • Pre contrast cuts (series). • I.V. contrast injection of 50ml (omnipaque300). • Post contrast cuts (Repeat the pre contrast cuts). • The same window level & window width for the pre and post contrast images on the films.

  21. Possibility of fracture Computed tomography • Two films are printed : • The 1st is soft tissue. • The second is bone window.

  22. Computed tomography Scout for sella axial Scout for sella coronal

  23. CT for pituitary fossa Using conventional CT the patient must be put in prone position. With multi detectors helical it is no longer required because reformation can be made in any projection with out loss of resolution. High resolution CT is needed for small adenoma.

  24. Continue CT of pituitary Gland Pre and post contrast images • 2mm cut for high resolution. • Zooming. • Sometime dynamic CT is required.

  25. CT of the neck • Patient preparation: • Fasting for 3Hours before the examination • Contrast: • Depend on the examination • 100-150 ml nonionic contrast medium (omnipaque 300) Bolus injection of the contrast for spiral CT

  26. Positioning: • Supine • Arms along the sides of the body • Immobilization of the head Parameters: • Starting at floor of the mouth • Ending at supraclavicular fossa • Respiration suspended in expiration with no swallowing.

  27. Computed tomography Scout for neck

  28. Computed tomography • Unit controls: • Scanogram AP and/or lateral • Gantry tilt depend on examination and patient • Slice thickness 4mm • Soft-tissue window and bone window if needed

  29. Computed tomography

  30. CT scan of the chest Computed tomography

  31. Computed tomography • Patient preparation: • Fasting for 3Hours before the examination • Chest x-ray in two projection • Positioning: • Supine • Arms folded behind the head

  32. Computed tomography • Parameter: • Starting at the lung apex • Respiration suspended in inspiration

  33. Computed tomography • Unit controls: • Scanogram AP • Gantry tilt 0º • Slice thickness 7mm • Soft-tissue (Mediastinal) window • Lung window

  34. Mediastinal window Computed tomography Lung window

  35. In pathological findings Computed tomography • Reduce the slice thickness • Interstitial diseases use the high resolution technique with slice thickness 2mm slice in lung window • For high resolution of lung parenchyma no I/V contrast is needed

  36. CT Scan of the Abdomen

  37. Certain factors or conditions may interfere with the accuracy of a CT scan of the abdomen. These factors include: metallic objects within the abdomen, such as surgical clips barium in the intestines from a recent barium study stool and/or gas in the bowel Computed tomography

  38. Computed tomography • Patient preparation: • Fasting 4-6 hours before the examination • Radiologist sometime need abdominal U.S • Oral laxative must be given • I/V buscopan is required at the time of examination • Any metallic foreign must be removed • Preferably the patient should be in hospital gown

  39. Computed tomography • Contrast Media: • Oral contrast • At mid night before the day of the examination .800ml of contrast media (5% Gastrografin + 95% water), the patient asked to drink 700ml during these hours • The last 100ml immediately before the exam • Replaced now by oral water and mannitol. • I.V. contrast • 100 ml nonionic contrast (omnipaque 300)

  40. Computed tomography

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  45. Non contrast CT of the abdomen include Urinary tract evaluation ( stone protocol ) Emergency CT for appendicitis Abdominal trauma

  46. Computed tomography

  47. CT for lumbar spine Computed tomography

  48. Computed tomography • Patient preparation: • For routine test no preparation • Contrast: • No contrast in routine examination

  49. Computed tomography

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