CT scans can show a tumor's shape, size,and location. They can even show the blood vessels that feedthe tumor – all without having to cut into thepatient. By comparing CT scans done over time, doctorscan see how a tumor is responding to treatment orfind out if the cancer has come back aftertreatment.
The difference between an MRI and CTscan
The biggest difference is that MRIs (magnetic resonanceimaging) use radio waves and CT (computed tomography)scans use X-rays. While both are relatively low risk, thereare differences that may make each one a better optiondepending on the circumstances.How long will the scan take? The timerequired will depend upon the type of scan. If oral contrastis required, about 45 to 60 minutes is needed for the contrast tomove through your digestive tract. Actual scan times varyfrom a few seconds to several minutes.
Like CT scans, MRI creates cross-section picturesof your insides. MRI is very good at finding and pinpointingsome cancers. An MRI with contrast dye is the bestway to see brain tumors. Using MRI, doctors cansometimes tell if a tumor is benign (not cancer) ormalignant (cancer).
Because radiation is not used, there is no riskof exposure to radiation during an MRI procedure.However, due to the use of the strong magnet, MRIcannot be performed on patients with: Implantedpacemakers.
Some cancers, such as prostate cancer,uterine cancer, and certain liver cancers, are prettymuch invisible or very hard to detect on a CT scan.Metastases to the bone and brain also show up better on anMRI.
At the low doses of radiation a CT scan uses,your risk of developing cancer from it is so small that it can't bereliably measured. Because of the possibility of an increased risk,however, the American College of Radiology advises that no imagingexam be done unless there is a clear medical benefit.
The scans use two kinds of technology:
- CT (computed tomography) scan: Takes many X-ray pictures of thebody.
- PET (positron emission tomography) scan: Radioactive materialis injected into the body and collects in areas with cancer.
MRI of the heart lets your doctor see if yourheart is damaged from a heart attack, or if there is lack of bloodflow to the heart muscle because of narrowed or blockedarteries. MRI of the brain is used to diagnosestroke, aneurysm and other brain abnormalities.
Magnetic resonance imaging (MRI) of the body usesa powerful magnetic field, radio waves and a computer to producedetailed pictures of the inside of your body. It may be usedto help diagnose or monitor treatment for a variety ofconditions within the chest, abdomen and pelvis.
In a year, the average person gets about 3 millisieverts(mSv), the units that scientists use to measure radiation.Each CT scan delivers 1 to 10 mSv, depending on thedose of radiation and the part of your body that'sgetting the test. A low-dose chest CT scan is about1.5 mSv.
