Virtual colonoscopy, also known as CT colonography, is a non-invasive medical imaging procedure that uses x-rays and computers to produce 2D and 3D images of the rectum and entire colon. It can detect polyps and other abnormalities. The colon and rectum are parts of the large intestine; the rectum is the final straight portion. Virtual colonoscopy is performed to screen for or follow up on colon cancer, investigate symptoms like abdominal pain or blood in the stool, and check for polyps. It has advantages over standard colonoscopy in being less invasive, safer, and allowing patients to return to normal activities sooner, but it cannot be used to biopsy or remove polyps and may miss some smaller polyps

1. Virtual Colonoscopy
1

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. What are the rectum and colon?
3

4. Colon
 The colon is also called the large intestine
4

5. Rectum
 Final straight portion of the large intestine.
5

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. Colon polyps
An abnormal growth of tissue projecting from
a mucous membrane
7

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. 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

10. 10

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

12. 12

13. Direction of rotation
Rotating x ray
source
Motorized platform
13

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. 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. Risks
The risks of virtual colonoscopy include
 exposure to radiation and
 perforation—a hole or tear in the
lining of the colon.
16

17. Bibliography
 http://www.nlm.nih.gov/medlineplus/ency/ar
ticle/007253.htm
 http://digestive.niddk.nih.gov/ddiseases/pubs
/virtualcolonoscopy/
 http://en.wikipedia.org/wiki/Virtual_colonosc
opy
17

18. 18