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Frequently Asked Questions: CT Scan

Wednesday, March 21, 2012 - 14:08

Contributing Author: Guy Slowik FRCS

Here are some frequently asked questions related to CT scan.

Q: Does CT hurt?

A: CT imaging itself is painless. The patient is required to remain motionless during the examination (which is difficult for some people), but the actual scan causes no bodily sensation.

Q: How long will the CT take?

A: The length of a complete CT examination varies, depending on the type of CT required. Procedures usually take between 10 and 45 minutes. Some of the more complicated CT examinations take longer than 45 minutes.

Q: Do all CT scans require the administration of acontrast agent?

A: Not all CT examinations require the use of a contrast agent. When a contrast agent is required, it is because the radiologist and referring physician determine that it is necessary for diagnosis. Contrast agents are considered to be safe and side effects are uncommon. The benefits associated with the improved imaging of particular organs generally outweigh the low risk of allergic reaction.

Q: Is it all right to have a CT during pregnancy?

A: Pregnant women should not have a CT, or any other x-ray examination, while in the first trimester (the first three-month period) of the pregnancy. Other exams, such as ultrasound, are available to help diagnose a medical condition in such cases.

Q: What is the difference between CT and MRI?

A: CT and MRI differ in two basic ways.CT uses x-rays to detect and record the radiation absorbed by different tissues, and sends the data to a computer to transform into images. MRI does not use x-rays. Instead, MRI employs a powerful magnetic field to monitor the nuclei of hydrogen atoms in water, the most abundant element in the body. When subjected to the magnetic field of an MRI, the hydrogen protons are knocked out of alignment and emit a radiofrequency signal that is detected by the MRI machine, which then processes the signals into images.CT scans usually show little differentiation in soft tissues, but highlight solid structures, like calcium deposits or kidney stones. MRI scans emphasize detailed tissue structures due to differences in water content.

CT Scan