Virtual colonoscopy


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Medical imaging technique for colon

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Virtual colonoscopy

  1. 1. Virtual Colonoscopy 1
  2. 2. What is virtual colonoscopy?        Medical imaging procedure. Also known as CT colonography. Non invasive procedure. uses x rays and computers. 2D and 3D images of rectum and entire colon. display them on a screen. can provide 3D reconstructed endoluminal views of the bowel. 2
  3. 3. What are the rectum and colon? 3
  4. 4. Colon  The colon is also called the large intestine 4
  5. 5. Rectum  Final straight portion of the large intestine. 5
  6. 6. Why the Test is Performed  Follow-up on colon cancer or polyps  Look for the cause of: • Abdominal pain, changes in bowel movements, or weight loss • anemia due to low iron • Blood in the stool • Screen for cancer of the colon 6
  7. 7. Colon polyps An abnormal growth of tissue projecting from a mucous membrane 7
  8. 8. How to Prepare for the Test  Patient need to empty bowels before the exam  patient will usually be asked to take laxatives or other oral agents at home the day before the procedure to clear stool from the colon. 8
  9. 9. How the Test is Performed  Patient is asked to lie on his/her left side on a narrow table that is connected to an MRI or CT scan machine.  knees will be up towards the chest.  A small, flexible tube will be inserted into rectum.  Air is pumped through the tube to make the colon bigger and easier to see. After this is done, patient will be asked to lie in supine position. 9
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  11. 11.  The table moves through the scanner to produce a series of two-dimensional cross-sections along the length of the colon.  A computer program puts these images together to create a three-dimensional picture that can be viewed on the video screen .  patient is asked to hold his/her breath during the scan to avoid distortion on the images.  The scan is then repeated with the patient lying in a prone position . 11
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  13. 13. Direction of rotation Rotating x ray source Motorized platform 13
  14. 14. Advantages  Virtual colonoscopy is less invasive, safer, and takes less time than a regular colonoscopy.  A thin tube to insert air into the colon is placed in the rectum rather than a long flexible tube that is moved up your colon.  Patients do not require anesthesia or sedation and can return home on their own or get back to work immediately after the test.  VC provides clearer, more detailed images 14
  15. 15. Disadvantages a radiologist cannot take tissue samples (biopsy) or remove polyps during VC, so a conventional colonoscopy must be performed if abnormalities are found.  may not show polyps smaller than 10 mm  There is a slight risk that the CT scan can interfere with implanted or external medical devices.  15
  16. 16. Risks The risks of virtual colonoscopy include  exposure to radiation and  perforation—a hole or tear in the lining of the colon. 16
  17. 17. Bibliography  ticle/007253.htm  /virtualcolonoscopy/  opy 17
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