What is CT?
Computed tomography (CT scan) is a medical imaging procedure that uses computer-processed X-rays to produce tomographic images or 'slices' of specific areas of the body. These cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines.
CT has become an important tool in medical imaging and is increasingly used for preventive medicine or screening for disease, for example CT colonography for patients with a higher risk of colon cancer, or coronary CT or calcium scoring for patients with higher risk of heart disease.
CT at MIC
MIC, operates a 128 slice CT scanner with low dose technology to ensure our patients receive high quality exams with minimal radiation exposure.
An MIC radiologist will analyze the images and send a detailed report to the physician who referred you for the exam. The referring physician will discuss the results with you.
Follow-up examinations may be necessary, and your doctor will explain the reason why another exam is needed. Sometimes a follow-up exam is done because a suspicious or questionable finding needs clarification with additional views or a special imaging technique. A follow-up examination may be necessary so that any change in a known abnormality can be monitored over time. Follow-up examinations are sometimes the best way to see if treatment is working or if an abnormality is stable over time.
Cardiac Health Screening
"Every seven minutes, someone in Canada dies from heart disease or stroke." — Heart and Stroke Foundation of Canada
Coronary artery disease (CAD; also atherosclerotic heart disease) is the most common type of heart disease and cause of heart attacks. The disease is caused by plaque building up along the inner walls of the arteries of the heart, which narrows the arteries and restricts blood flow to the heart. It is the leading cause of death worldwide.
While the symptoms and signs of coronary artery disease are noted in the advanced state of disease, most individuals with coronary artery disease show no evidence of disease for decades as plaque buildup occurs, often resulting in a sudden heart attack.
Risk factors for coronary artery disease:
- Diets heavy in saturated fat
- Physical inactivity
- Prolonged stress
- A family history of heart disease
- Being overweight
Coronary CT Angiography (CCTA)
As a diagnostic test or in the routine screening of individuals risk of heart disease, CCTA can be a potentially lifesaving tool. CT is a non-invasive, fast and simple imaging procedure delivering crucial diagnostic information.
CCTA can identify signs of heart disease other diagnostic methods such as ECG's or stress tests can't. CCTA can detect both calcified plaque and non-calcified plaques. Coronary CT angiography is a fast, safe non-invasive test to assess the degree of narrowing of the coronary arteries. It may reassure your physician that your coronary arteries are normal or that lifestyle modifications or medication may be beneficial.
How should I prepare?
You should wear comfortable, clothing to your exam. You may be given a gown to wear during the procedure.
All preparation instructions will be provided to you by a member of MIC's staff and any required medications (beta blockers) will be provided to you in advance of your examination instructions.
On the day before and day of your exam, you will be asked to avoid:
- diet pills and caffeinated drinks such as coffee, tea, energy drinks or sodas. These may increase heart rate and limit the ability of the exam to evaluate for plaque in the coronary arteries.
- Viagra or any similar medication. They are not compatible with the medications you will receive during the procedure.
How is the procedure performed?
A nurse will insert an intravenous (IV) line into a vein in your arm to administer contrast material (dye) during your procedure.
The technologist will place small, sticky electrode patches on these areas. Men may require a small area of hair to be shaved on their chest to help the electrodes stick. The electrodes are attached to an electrocardiograph (ECG) monitor, which shows your heart's activity during the test.
You may be asked to hold your breath during the scanning.
Your intravenous line will be removed.
Including all preparations, the coronary CTA scan usually takes about 15 minutes if the heart rate is slow and steady. It may take longer if the baseline heart rate is fast and beta-blocker is given to slow it down. If the beta-blocker is given by mouth it generally will require at least one hour to take effect. If the medication is injected into a vein (intravenously), it may still require multiple doses and up to 20 minutes to reach the slower heart rate.
What will I experience during and after the procedure?
Other than the needle stick when the IV line is placed, most CT exams are fast, easy and painless.
After the procedure, your vital signs will be monitored and you may have a brief wait while your heart rate increases. A quiet lounge area will be provided for your comfort.
The results of your examination will be provided to your primary care physician.
If you think you are at risk for CAD, talk to your physician about CCTA.
Cardiac Calcium Scoring
A coronary calcium scan is a screening test for people who have no symptoms of heart disease.
Many people only learn that they have heart disease when they have a heart attack. A coronary calcium scan is one way to find out if you have early heart disease. After you know your risk, you can make lifestyle changes such as eating a heart-healthy diet, getting more exercise, and quitting smoking. But if you're worried about heart disease, you can make these changes even if you don't have the test.
A coronary calcium scan can give your doctor more information about your risk for heart disease, especially if you already have risk factors. Calcium scoring can also help guide medication changes in order to reduce cholesterol.
A virtual colonoscopy can be used to screen for precancerous and cancerous growths in the colon or rectum (colorectal cancer), such as polyps or tumors.
The key to surviving colorectal cancer is early detection. Identified early enough, polyps in the colon can be removed before they become cancerous. The most common diagnostic method is the conventional colonoscopy which is invasive and can be complicated by other risk factors. A virtual colonoscopy performed by MIC is less invasive and is extremely accurate in the detection of polyps or other masses.
Routine screening of the colon should begin at age 50 (age 40 for individuals with a family history of colorectal cancer or other diseases of the bowel).
How should I prepare?
Critical to the success of your exam is a thorough bowel cleanse. MIC will provide you with all of the necessary dietary information and medications that you require to prepare for your exam.
Be sure to inform your physician if you have heart, liver or kidney disease to be certain that the bowel prep will be safe. Your physician can advise you on dietary restrictions prior to the exam. You will be able to resume your usual diet immediately after the exam.
Women should always inform their physician and the CT technologist if there is any possibility that they may be pregnant.
How does the procedure work?
With CT scanning, numerous x-ray beams and a set of electronic x-ray detectors rotate around you, measuring the amount of radiation being absorbed throughout your body. At the same time, the examination table is moving through the scanner, so that the x-ray beam follows a spiral path. A special computer program processes this large volume of data to create two-dimensional cross-sectional images of your body, which are then displayed on a monitor. This technique is called helical or spiral CT.
CT imaging is sometimes compared to looking into a loaf of bread by cutting the loaf into thin slices. When the image slices are reassembled by computer software, the result is a very detailed multidimensional view of the body's interior.
For CT colonography, the computer generates a detailed 3-D model of the abdomen and pelvis, which the radiologist uses to view the bowel in a way that simulates traveling through the colon. This is why the procedure is often called a virtual colonoscopy. Two dimensional (2-D) images of the inside of the colon as well as the rest of the abdomen and pelvis are obtained and reviewed at the same time.
How is the procedure performed?
The technologist begins by positioning you on the CT examination table, usually lying flat on your back or less commonly, on your side or on your stomach. Straps and pillows may be used to help you maintain the correct position and to help you remain still during the exam. Depending on the part of the body being scanned, you may be asked to raise your arms over your head.
A very small, flexible tube will be passed two inches into your rectum to allow CO2 to be gently pumped into the colon. The purpose of the gas is to distend the colon as much as possible to eliminate any folds or wrinkles that might obscure polyps from the physician's view. This can create some discomfort; much like abdominal cramps. It only lasts for a few minutes during the procedure.
The entire examination is usually completed within 15 minutes.
What will I experience during and after the procedure?
The vast majority of patients who have CT colonography report a feeling of fullness when the colon is inflated during the exam, as if they need to pass gas. Significant pain is uncommon, occurring in fewer than 5 percent of patients. A muscle-relaxing drug may be injected intravenously or subcutaneously to lessen discomfort, but this is seldom necessary. The scanning procedure itself causes no pain or other symptoms.
After a CT exam, you can return to your normal activities.
What are the benefits vs. risks?
- This new minimally invasive test provides both 2-D and 3-D images that can depict many polyps and other lesions as clearly as when they are directly seen by conventional colonoscopy.
- CT colonography has a markedly lower risk of perforating the colon than conventional colonoscopy. Most people who undergo CT colonography do not have polyps, and can be spared having to undergo a full colonoscopy.
- CT colonography is an excellent alternative for patients who have clinical factors that increase the risk of complications from colonoscopy, such as treatment with a blood thinner or a severe breathing problem.
- Elderly patients, especially those who are frail or ill, will tolerate CT colonography better than conventional colonoscopy.
- CT colonography can be helpful when colonoscopy cannot be completed because the bowel is narrowed or obstructed for any reason, such as by a large tumor.
- If conventional colonoscopy cannot reach the full length of the colon—which occurs up to 10 percent of the time—CT colonography can be performed on the same day because the colon has already been cleansed.
- CT colonography provides clearer and more detailed images than a conventional barium enema x-ray examination.
- CT colonography can detect abnormalities outside of the colon, including early-stage malignancies and potentially dangerous conditions, such as abdominal aortic aneurysms.
- CT colonography is tolerated well. Sedation and pain relievers are not needed, so there is no recovery period.
- There is a very small risk that inflating the colon with air could injure or perforate the bowel. This has been estimated to happen in fewer than one in 10,000 patients.
- There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis will generally outweigh the risk.
- The effective radiation dose for this procedure varies. See the Safety page (www.RadiologyInfo.org/en/safety/) for more information about radiation dose.
- Women should always inform their physician and x-ray or CT technologist if there is any possibility that they are pregnant. See the Safety page (www.RadiologyInfo.org/en/safety/) for more information about pregnancy and x-rays.
- CT scanning is, in general, not recommended for pregnant women unless medically necessary because of potential risk to the baby.
What are the limitations of CT Colonography?
CT colonography is strictly a diagnostic procedure. If any clinically significant polyps are found, they will have to be removed by conventional colonoscopy.
The ability of CT colonography to differentiate stool from artifacts and smaller polyps may not be as good as that of conventional colonoscopy.
CT colonography is not recommended for patients who have active Crohn's disease, ulcerative colitis, inflammatory bowel disease or diverticulitis, because of increased risk of perforating the colon.
Virtual Colonoscopy flythrough
CLICK HERE for our informational video explaining the technology behind virtual colonoscopy examinations.
"CT scanning reduced mortality from lung cancer in these high-risk individuals by 20%"— National Lung Cancer Study, Medical News Today [ May 7, 2013 ]
People who smoke or have smoked in the past are at risk for developing lung cancer. There is no way to predict who will develop lung cancer, traditionally tests are done if someone develops symptoms such as cough, difficulty breathing or coughing up blood.
Computed Tomography Screening
Computed Tomography (CT) produces extremely detailed images of the lungs using x-rays. Current equipment allows images to be produced with very low radiation; less than the background radiation one would experience in a year living a normal life.
Lung Cancer Screening with CT
Since very detailed images can be produced, small nodules or lumps can be detected within the lungs. Some may obviously represent lung cancer and can be immediately dealt with and treated. Many small nodules may not be related to lung cancer, but by repeating the CT images at regular intervals (1 year or less), nodules that are growing would be considered suspicious and can be further investigated.
Who Should Undergo Lung Cancer Screening
Recent evidence is strongest for those who are between 50-74 years old, have no symptoms (cough, difficulty breathing, coughing up blood), have smoked at least 30 pack years (ie, 1 pack per day for 30 years, 2 pack per day for 15 years, etc ...) and are either currently smoking or have quit smoking within the past 15 years. In these patients, there is a decreased chance of death from lung cancer due to earlier detection and management.
If you do not fit these criteria but have these or other symptoms, CT may still be appropriate for you, and you should talk to your physician.
People who have a history of cancer do not fit the specific criteria for screening CT, but CT studies should be guided by your symptoms, laboratory results and the plan you have discussed with your physician for followup.
Potential Outcomes of Lung Cancer Screening
The majority of examinations will be normal. Although this is reassuring, it does not mean you will not develop lung cancer in the future. Thus, further screening studies at regular intervals will be necessary. Currently, yearly screening CT studies are suggested until the age of 74.
Many studies will show small nodules (a few millimetres in size) that are not specific for anything. These will usually be followed on subsequent CT studies. Larger nodules may need further investigation. In some of these cases, other tests may be necessary to confirm that the nodules are cancerous or benign. For very small nodules, this may simply involve further CT studies to see if the nodules increase in size or resolve. For larger nodules, further imaging tests such as Positron Emission Tomography (PET) may be used. If indicated, more invasive procedures such as bronchoscopy, CT-guided lung biopsy, mediastinoscopy (using a camera to look for/biopsy lymph nodes), thorascopy (using a camera to look for/biopsy lung lesions) or surgical biopsy or resection may be necessary. In Alberta, the Alberta Thoracic Oncology Program (ATOP) will help guide the management of these suspicious nodules. If a suspicious nodule is detected, you will be referred to ATOP.
Due to the detail of CT, a not-insignificant proportion of studies (5-10%) will show significant findings that are not related to lung cancer. These would include but not be limited to: aortic aneurysm, interstitial lung disease, pneumonia, pneumothorax (air between the lung and chest wall), severe coronary artery calcification, rib or spine fractures, soft tissues masses. You and your physician will be notified of any of these findings so that appropriate management can be undertaken.
Risks of Lung Cancer Screening
Any CT study exposes you to radiation. Using our current equipment and the latest techniques, the dose is less than background radiation one would experience in a year living a normal life. However, since there is still radiation involved, getting screening CT (or any other CT study) should be considered in consultation with your physician.
A large percentage of nodules found on screening CT studies will be non-cancerous. This does not mean "normal", they may be due to infection or other causes. Often, the only way to confirm this (particularly for small nodules) is to see if they grow or resolve on subsequent CT studies. Although this may cause concern, if a nodule is so small that other tests would be of little use, even a cancerous nodule would be unlikely to cause significant complications.
As noted above, larger or growing nodules may require more invasive tests for a complete diagnosis. These tests (listed above) may result in complications but the complication rate is fairly low.