Download presentation
Presentation is loading. Please wait.
Published byCharles Matthews Modified over 9 years ago
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
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.