1. Dr Mohamed El Safwany, MD. Computed tomography

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

3. 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. Computed tomography

4. 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. Computed tomography

6. Operation console Gantry and Table Computed tomography

8. Head firstFeet first Computed tomography

9. 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.nauseabreathing difficulty 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. Computed tomography

10. 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).

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

12. 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.

13. Computed tomography

14. A CT scan is recommended to help: Evaluate acute cranial-facial traumaacute determine acute strokestroke Evaluate suspected subarachnoid or intracranial hemorrhage intracranial hemorrhage Evaluate headacheheadache Determine if there abnormal development of the head and neck Computed tomography

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

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

17. Unit controls 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. Computed tomography

19. Soft-tissue

20. Bone window Computed tomography

21. 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.

22. Possibility of fracture Two films are printed : 1) The 1 st is soft tissue. 2) The second is bone window. Computed tomography

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

24. 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.

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

26. 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

27. 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.

28. Computed tomography Scout for neck

29. 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 Computed tomography

31. CT scan of the chest Computed tomography

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

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

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

35. Mediastinal windowLung window Computed tomography

36. In pathological findings 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 Computed tomography

37. CT Scan of the Abdomen

38. 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

39. 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 Computed tomography

40. 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) Computed tomography

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

47. Computed tomography

48. CT for lumbar spine Computed tomography

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

51. Positioning: Supine and feet first Arms above the head The knees flexed 30º Parameters: Starting at xiphoid process Ending at the level of hip joint Respiration suspended in expiration Computed tomography

52. Unit controls Gantry tilt: 0º. Lateral scout view. Gantry tilt: parallel to the disc space Slice thickness: 3mm Computed tomography

53. Soft-tissue window Computed tomography Bone window

54. Text Book David Sutton’s Radiology Clark’s Radiographic positioning and techniques

55. Assignment Two students will be selected for assignment.

56. Question Define positioning and parameters of CT lumbosacral spine?

57. Thank You