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Frequently Asked Questions
Questions regarding Colon Cancer
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Question #1: | Why is it important for me to have a colon-screening exam?
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| The American Cancer Society reports colon cancer (also referred to as colorectal cancer) as the second leading cause of cancer related death in the United States. This is a shame considering colon cancer is the most preventable and treatable cancer with a survival rate of 90% if the abnormal growths are detected and treated before cancer spreads to other vital organs. However, only 37% of men and women over the age of 50 were screened for colon cancer last year. Pre-cancerous polyps can be present for years before invasive cancer develops and regular screening allows for early detection and prevention of colon cancer. Virtual colonoscopy is a safe, quick, and reliable screening method to protect yourself from colon cancer.
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Question #2: | What is Colon Cancer?
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Colon cancer, also referred to as colorectal cancer, is the second leading cause of cancer related death in the United States. Colon cancer affects 6% of the population in the United States and the American Cancer Society reports 57,000 colon cancer related deaths per year. Both men and women are at risk. Colon cancer is the most preventable cancer because it ordinarily develops from pre-cancerous polyps in the colon which can be easily screened. With early screening, pre-cancerous polyps can be removed before becoming cancerous. On average, abnormal growths in the colon follow a sequence of development from pre-cancerous polyps to cancerous polyps over a period of 7-10 years. For more information on colon cancer ask your primary care provider or visit the American Cancer Society website.
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Question #3: | What is a polyp?
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A polyp is an abnormal growth found on the inner wall of the colon or rectum. Some polyps are known to be the precursor of colorectal cancer. Polyps can be, benign (non-cancerous) or pre-cancerous. If caught early, pre-cancerous polyps can be removed before they may become cancerous. Research shows there is a correlation between type of polyp and polyp size. Smaller polyps (<6 mm) are usually benign, while larger (>8 mm) polyps have a potential of being pre-cancerous. The greater the size of the polyp the more likelihood the polyp is pre-cancerous. Small polyps <6 mm have less than 1% chance of becoming cancerous. Please note that about 85% of the colon cancer screening population will have no significant polyps. Virtual colonoscopy recommends removal of pre-cancerous polyps and follow-ups for small probable benign polyps.
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Questions regarding Virtual Colonoscopy
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Question #1: | What is virtual colonoscopy?
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| Virtual colonoscopy is a FDA approved, non-invasive procedure, which screens for colorectal cancer. Virtual colonoscopy uses a state-of-the-art simulation program to reconstruct abdominal computed tomography (CT) images into a three-dimensional (3D) replica model of the colon. A radiologist, with advanced training, uses the 3D simulated images to navigate your colon in order to identify tumors and pre-cancerous polyps. The radiologist is also able to identify other abnormalities outside of the colon from the abdominal CT scan.
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Question #2: | Who should have a virtual colonoscopy?
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American Cancer Society recommends colon cancer screening for both men and women over the age of 50. For those individuals with a positive family history of colon cancer (family members such as father, mother, brother, or sister), the American Cancer Society recommends colon cancer screening starting at the age of 40. Currently, there are several screening methods available but optical colonoscopy (also known as “conventional?or “traditional?colonoscopy) was the only option available for full colon screening exam. Virtual colonoscopy can visualize the entire colon and it is a convenient, non-invasive screening procedure that makes it easy to protect yourself from colon cancer. In addition, virtual colonoscopy is a good alternative for patients who have a history of incomplete optical colonoscopy, are allergic to IV sedation, or are hesitant to get screened because they perceive optical colonoscopy as invasive, risky, time-consuming or inconvenient.
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Question #3: | What is the difference between virtual colonoscopy and optical colonoscopy?
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Virtual colonoscopy is an abdominal CT scan where “pictures?of the abdomen are taken and then the images are reconstructed into a 3D replica of the colon. The images are then read by a trained radiologist to look for pre-cancerous polyps or abnormalities inside and outside your colon. For the optical colonoscopy exam (also known as “conventional?or “traditional?colonoscopy), a flexible tube that has a camera at the end is inserted into the rectum and manually manipulated by a gastroenterologist (GI doctor) all the way to the beginning of the colon called the cecum. On the way back from the cecum, the GI doctor slowly pulls out and looks for polyps. If polyps are found, these can be removed using available tools through the flexible tube. Please note that only about 15% of the screening population will actually require removal of pre-cancerous polyps.
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Question #4: | What are the advantages and disadvantages for virtual colonoscopy and optical colonoscopy?
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There are several advantages and disadvantages for both virtual colonoscopy and optical colonoscopy. Please refer to the summary chart below:
| Full Colon Screening Exam | Advantages | Disadvantages |
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95% to 99% visualization of the Colon
Requires no sedation and recovery time
Ability to screen outside the colon using abdominal CT images
Takes about 15 minutes for the exam
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Cannot Remove Polyps
Exposure to radiation
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| OC |
High accuracy
Can remove polyps at the time of the procedure
Discomfort from the procedure is not remembered due to the IV sedation
Takes about 2-4 hours including the post-sedation recovery time
Can only view the inner surface of the colon directly ahead and cannot view areas behind folds
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70% to 75% visualization
1/1000 to 1/1500 risk of perforation
10% of patients have failed/incomplete colonoscopy due to redundancy of the colon or large number of diverticuli
Risk of bleeding
Risk of complications related to IV sedation
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Virtual colonoscopy has been proven to be as effective and in some cases more effective than optical colonoscopy in detecting significant polyps. Virtual colonoscopy uses state-of-the-art software to visualize typically 95% to 98% of the colon. Using the virtual colonoscopy exams, radiologists can view your colon forwards [from the rectum (end of the colon) to the cecum (beginning of the colon)] and backwards (from the cecum to the rectum), hence are able to see behind folds and sharp turns. In addition, the software used to read virtual colonoscopy exams allows highlighting of the areas already seen in the colon and the radiologist can go back and easily examine the areas missed. On average, 70% to 75% of the colon is visualized in optical colonoscopy due to limitations of the procedure. Unlike optical colonoscopy, virtual colonoscopy can view the entire colon regardless of redundancy from the anatomy of the colon, or large number of diverticuli (out-pouches of the lining of the colon).
Optical colonoscopy requires sedation and a recovery period, virtual colonoscopy does not require patients to be sedated and patients can return to their normal activities immediately after the exam. In addition, there are serious risks with optical colonoscopy. Optical colonoscopy has risks of bleeding, complications with the IV sedation, and 1 in 1500 patients that undergo optical colonoscopy may have their colon injured, resulting in a tear or perforation. On the other hand, these risks are not present with virtual colonoscopy because of the non-invasive nature of the exam. Virtual colonoscopy exam takes about 15 minutes while optical colonoscopy takes 2-4 hours because of the required recovery time from the IV sedation.
Both virtual colonoscopy and optical colonoscopy need to distend the colon in order to visualize the inside of the colon. Optical colonoscopy uses plain room air to distend the colon, while virtual colonoscopy uses carbon dioxide gas (CO2) which is as safe as using room air. CO2 is reabsorbed by your body much faster and the bloating feeling felt during the exam dissipates often within minutes from the end of the virtual colonoscopy exam. Room air takes usually at least an hour to hours to dissipate from the colon.
Optical colonoscopy can remove any polyp that may be seen during the exam. Virtual colonoscopy cannot remove polyps due to the fact that only “pictures?are taken, and some patients may have to undergo optical colonoscopy to have pre-cancerous polyps removed. Please note that about 85% of the screening population has no significant polyps. One beneficial advantage of the virtual colonoscopy is the ability to screen outside your colon using the abdominal CT images. The radiologists will read the whole abdominal CT scan and any abnormalities or potential abnormalities seen will be reported as well for further evaluation.
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Question #5: | How accurate is virtual colonoscopy compared to conventional colonoscopy?
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A recent clinical trial conducted at Walter Reed Army Medical Center-Washington, D.C., National Navy Medical Center-Bethesda, MD and Navy Medical Center-San Diego, CA concluded that virtual colonoscopy is slightly more accurate than conventional colonoscopy in detecting significant colonic polyps. This study was published in the New England Journal of Medicine in 2003. 1,233 screening patients for colon cancer were recruited and each patient underwent first virtual colonoscopy and within two hours underwent optical colonoscopy to compare results. The study compared the percentage of polyps found by both virtual colonoscopy and optical colonoscopy. See chart below:
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Polyp Size Threshold
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> 6 mm
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> 8 mm
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>10 mm
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Virtual Colonoscopy
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88.70%
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93.90%
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93.80%
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Optical Colonoscopy
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92.30%
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91.50%
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87.50%
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Question #6: | How is the virtual colonoscopy procedure performed?
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You will be asked to use the restroom right before the exam to insure your bowel is as empty as possible. You will be then asked to change into a hospital gown. You will be instructed to lie on your side on the CT scanner table. A trained technician will place a short, flexible, lubricated tube into your rectum. Through this tube a machine will slowly fill your colon with CO2 (Carbon Dioxide: a colorless, odorless gas) so that it is distended enough to get an accurate reading. The machine has a pressure sensor and it will “sense?that the colon is distended enough and no more gas will be pumped in. Every patient will receive different amounts of gas depending on how large the colon is. You may feel some discomfort from the distention. Most patients rate the level of discomfort as “tolerable?and most of the discomfort is immediately relieved as soon as the procedure is completed.
The CT scanner will then take pictures of your abdomen. During the scan you will periodically need to hold your breath for several seconds. Pictures will be taken while you are lying on your back and on your stomach. When you lay on your stomach you should feel significant relief from the abdominal pressure. The procedure from start to finish should take no longer than 15 minutes. You will be asked to use the restroom right after the exam is completed and to then change back to your clothes. You will be instructed to go back to a regular diet and to your normal schedule. There is no recovery period so you can leave right after the exam. After the CT scanner compiles the images, they are then sent to a computer that uses 3D technology to recreate your colon into a computerized 3D replica. A trained radiologist will interpret the 3D image of your colon as well as the abdominal CT scan to detect significant polyps and other abnormalities.
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Question #7: | Is the procedure painful?
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Since the procedure uses a non-invasive technique, most patients do not feel any severe pain. Most patients describe the discomfort as feeling “bloated" Some patients may feel cramping similar to gas pains. If present, the “gas cramping pain" lasts about 3-4 minutes and subsides once the machine senses enough distention in the colon and no more CO2 gas is pumped in. The “bloated" feeling should pass within 30 minutes and leave no lasting effect.
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Question #8: | How can I get a virtual colonoscopy exam?
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You must be enrolled in Tricare or Tricare Prime to be eligible for virtual colonoscopy at Walter Reed Army Medical Center. Any Health Care Provider within the Tricare system can order a virtual colonoscopy. In other words, you do not necessarily need a referral to see a gastroenterologist (GI doctor) first. You can just see your regular Health Care Provider to have him or her put in the orders required for the virtual colonoscopy exam. If you have any questions, or if your Health Care Provider has any questions about how to put the orders in the system, please call 202-782-0892. Once the orders were put in by the Provider, please call 202-782-6188/0892 to schedule the exam or you may come in person to our clinic at Walter Reed Army Medical Center, section 1G of the Department of Radiology.
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Patient questions about the prep
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Question #1: | What medications are prescribed for this procedure?
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There are two types of prep kits available for virtual colonoscopy. For most patients the Fleets Phosphosoda prep kit should be used. This kit includes four medications: CT Barium, Gastroview, Dulcolax, and Fleets Phosphosoda.
Some patients should NOT take Fleets Phosphosoda as the laxative. Patients with a history of severe heart disease, kidney disease and other serious debilitating diseases should talk with their primary care provider about the side effects of Fleets Phosphosoda. A second prep kit was designed, specifically with these patients in mind and includes three medications: CT Barium, Gastroview, and Colyte.
CT Barium and Gastroview are oral contrast agents that are used in radiographic studies. Dulcolax pills are stool softeners, and Fleets Phosphosoda and Colyte are oral laxatives that promote bowel movements. All of these medications will work together to cleanse and tag your colon, making the detection of significant polyps and other abnormalities easier.
Note: If you have a history of severe heart disease, kidney disease, and/or other serious debilitating disease and believe you have received the wrong medication please contact our office before starting your prep.
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Question #2: | Why is it necessary to take prep medications?
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Virtual colonoscopy requires medications that clean out the colon and tags (highlights) stool. Without the proper medication to clean out the colon, remaining stool would make it difficult to view the colon wall. It is also important to take oral contrast, which is a tagging agent. Oral contrast will help the radiologist tell the difference between polyps and any remaining stool. It is important that these medications are taken exactly as instructed so that the most accurate and reliable reading is obtained. If the prep is done incorrectly the exam may have to be repeated.
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Question #3: | Which pharmacies carry the prep set?
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The Virtual colonoscopy prep set is available through the following outpatient pharmacies:
Walter Reed Army Medical Center
Outpatient Pharmacy
(202) 782-4703
Dewitt Army Hospital
Ft. Belvoir, VA
(703) 805-2202
Kimbrough Health Clinic
Ft. Meade, MD
(301) 677-8288/8302
FT. Detrick AHC
Frederick, MD
(301)-619-2850
Rader AHC
Ft. Myer, VA
(703) 696-3540
DiLorenzo TRICARE
Pentagon, Corr8/Ering
(703) 692-8692/91
Fairfax FHC
Fairfax, VA
(703) 849-8191
Malcolm Grow Med Center
Andrews AFB, MD
(240) 857-4567
Woodbrigde FHCC
Woodbridge, VA
(703)-490-9698
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Question #4: | What is Oral Contrast and why do I need to take it?
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The purpose of oral contrast is to make certain organs or tissues more recognizable during radiological procedures. Virtual colonoscopy uses oral contrast to mark stool remaining in the colon. This helps the radiologist differentiate between stool and other abnormalities in the colon. It is very important that this medication be taken in its entirety to get the best possible results. If not taken properly the exam may have to be repeated.
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Question #5: | Will any of the prep medications interact with any health problems I have?
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There are two prep kits available. Depending on your medical history your primary care provider will prescribe the correct prep kit. If you have a history of kidney disease, severe heart disease, or are currently under a physicians care please discuss with your primary care provider which prep kit would be right for you. If you have any questions or concerns please contact the Virtual Colonoscopy Center before you start the prep.
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Question #6: | I did not receive the full prep kit. What should I do?
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If you believe you are missing an item from the prep kit, please call your physician to inform them that you do not have the full kit. Or, you can call the Virtual Colonoscopy office at (202) 782-0892.
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Question #7: | Do I need to follow a specific diet prior to the exam?
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You must follow a clear liquid diet the day before and day of the exam. You should not eat any solid foods on these two days. Three days before your exam consider a low fiber (no whole grains or high fiber foods) diet. Remember, all day the day before and the day of the exam you are to consume only clear liquids. At no time in these two days are you to have solid food. You will be back on a regular diet as soon as the exam is completed.
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Question #8: | What is acceptable on a clear liquid diet?
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A clear liquid generally refers to any liquid you can see through. This includes juices with no pulp, hard candy, broths, and gelatin. *Please click here to see more examples of acceptable clear liquids* You cannot have any solid food all day the day before or the day of your exam. Once the exam is completed you can return to a normal diet.
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Question #9: | Do I need to stop taking any medications prior to the exam?
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You should continue to take prescribed medications as you normally would. This procedure should not cause you to miss or skip doses of your daily-prescribed medications. **Do NOT skip your blood pressure or heart medications** If needed, you can take over the counter medications such as aspirin, Ibuprofen (Motrin), and Acetaminophen (Tylenol). Avoid taking your regular medications within 2 hours of your virtual colonoscopy prep medications to avoid absorption issues.
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Question #10: | What if I normally take pills for Diabetes?
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If you normally take pills orally for diabetes twice a day, on the day prior to your exam take the AM dose but skip the PM dose. You will be on a strict clear liquid diet and you will not need to take the PM dose. On the morning of the exam, wait to take your AM dose after the exam is completed and once you start eating regular solid food again. If you normally take one pill orally for diabetes once a day, on the day prior to your exam take the dose in the morning. On the morning of the exam, again, wait to take your pill for diabetes after the exam is completed and you are back on a regular diet again.
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Question #11: | There are some steps in the instructions that I do not understand. Who can I contact if I have questions?
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If you have any questions or concerns, please call the Virtual Colonoscopy office at (202) 782-0892
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Additional Questions
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Question #1: | Will this procedure cause me to experience claustrophobia (fear of enclosed spaces)?
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The CT scanner is a short, open device that is shaped like a giant ring or doughnut. At no point during the exam is your body fully enclosed. The ring device surrounds only the body part being scanned; you should not experience claustrophobia.
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Question #2: | When and where should I arrive for the procedure?
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You will be asked to arrive at least one hour prior to your appointment time to take the last dose of Gastroview, which has a laxative side effect. You can bring your own juice to chase it with or use our vending machines. Restrooms are available near the waiting room. The Virtual Colonoscopy Center is located within section 1G of the Radiology Department, First Floor of the Main Hospital. When you arrive, please inform the front desk of your name, time of appointment, and ask for a patient history form and the virtual colonoscopy information sheet.
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Question #3: | Will I need someone for transportation to and from the exam? When can I resume normal activities?
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Virtual colonoscopy requires no sedation, so you do not need someone to drive you to or from the exam. After the exam there is no observation or recovery period, and you can resume your regular daily activities.
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Question #4: | When and how will I find out the results of the exam?
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After a trained radiologist interprets the exam, a report will be mailed to your home address and your referring physician will also be notified of the results. Your physician will receive a full color report detailing the findings and recommendation from the exam within 3 business days of your exam. You should receive your report from the Virtual Colonoscopy office within two weeks of your exam.
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Question #5: | What is a CT Scan?
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A CAT scan or a CT scan is a form of x-ray imaging that produces cross-sectional images of the body. The scanner itself is a short, open chamber with no enclosed tunnel. It does NOT interfere with metal stents or electronic devices such as pacemakers. CT scanners use computers to record the amount of x-ray beams passing through the body. By creating a series of CT images (slices) down the body, the radiologist can look at each image and get an accurate indication of position, size, and density of objects within the body. Virtual colonoscopy takes all of the slices and recreates them into a 3D image of your colon that can be rotated and looked at from various directions.
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