CT scan radiation
exposure is small when compared to the benefits it yields when you really need to have one. CT Scan radiation comes from an x-ray beam and is used with care by trained and qualified professionals. Radiologists and CT Technologists have been trained to use the minimum amount of radiation necessary to obtain the needed results. The benefits greatly outweigh the risk of harm when a CT Scan is neccessary.
(X-ray) Radiologic Technologists and especially CT Technologists are very careful about the amount of radiation exposed to you. They will only use what's absolutely needed to get a good image.
Exposure time from one single chest x-ray can be less than 1/10th of a second, like taking a picture with a camera. Radiation exposure from CT Scan is higher. This is because the CT x-ray beam is on while the table you're laying on passes you through it which can take up to several seconds.
An article from Reuters UK
addresses the concerns many people may have about the amount of radiation exposure from CT Scans and may help alleviate radiation fear.
Sometimes the need for an x-ray during pregnancy is necessary. One medical x-ray image does not pose a critical risk to a developing unborn baby but there may be a small likelihood of causing illness or complications. However, CT exposure levels to an unborn child, especially in the first trimester are too high.
Seek the advice of your physician if you are pregnant and need an x-ray. The actual risk depends on how far along the pregnancy is and on the type of x-ray used.
Ultrasound doesn't use x-ray to produce images, it uses sound waves. That's why it's the exam of choice for pregnant women.