How much radiation is in a CT scan?
A typical adult CT delivers an effective dose of about 1–10 millisieverts (mSv) depending on the body region. For comparison: a chest X-ray is about 0.1 mSv, a transatlantic flight is about 0.05 mSv, and the average person in the United States receives about 3 mSv per year from natural background sources.
A head CT is typically around 2 mSv; a chest CT around 7 mSv; an abdomen/pelvis CT around 8–10 mSv. Low-dose lung cancer screening CT runs about 1.5 mSv.
What ALARA actually means
ALARA is the radiology profession's commitment to use the lowest radiation dose that still answers the clinical question. At Precise Imaging this means automatic exposure control on every scanner, iterative reconstruction algorithms that maintain image quality at lower dose, pediatric-specific protocols, and protocol review by our medical physicist on a rolling basis.
Children and dose
Children are more radiosensitive than adults and have a longer life expectancy in which any future risk could manifest. Every pediatric CT at Precise Imaging uses a size-based dose protocol — "child-size the dose" — that is significantly lower than the standard adult protocol. We follow Image Gently campaign recommendations on every pediatric study.
When CT is the right test
CT is often the best choice for trauma, acute abdominal pain, suspected lung disease, suspected stroke, kidney stones, and vascular emergencies — situations where speed and detail of bones, lungs, and blood vessels matter most. For many other indications, ultrasound or MRI can answer the same question without radiation, and our radiologists routinely suggest alternatives when appropriate.
Repeat CT scans and cumulative dose
If you have had multiple CTs for the same condition, ask whether the next scan is necessary or whether a different test could answer the question. We are happy to share prior reports and images with your provider so duplicate scans can be avoided. Our radiologists will reach out to your provider if a requested study seems duplicative.
If this applies to you
- Ask your provider what specific question the CT is meant to answer.
- Bring or request prior CT images on CD so the new scan can be compared and not duplicated.
- Tell us if you are or could be pregnant.
- For children, confirm with our team that a pediatric-specific protocol will be used.
- Ask for a copy of your dose report — we are happy to provide it.
Call us before your appointment if…
- You are or could be pregnant.
- You have had multiple CT scans of the same area recently.
- You are scheduling a CT for a child and want to confirm pediatric protocols.
- You want to discuss whether MRI or ultrasound could answer the same question.
This page is general patient education and does not replace the medical advice of your physician. It describes how Precise Imaging operates today and is not a substitute for the specific instructions on your appointment confirmation. Always discuss your medical history with the provider who ordered your exam.
Frequently asked questions
Is CT radiation dangerous?
The radiation dose in a single appropriate CT is small. The benefit of an accurate diagnosis almost always outweighs the very small theoretical risk. We use dose-reduction technology and the lowest dose that still answers the clinical question.
How much radiation is in a CT compared to other things?
A chest CT is roughly equivalent to two years of natural background radiation. A chest X-ray is roughly 10 days of background. An abdominal CT is roughly three years of background. Numbers vary by body region and patient size.
Is it safer to get an MRI or ultrasound instead?
MRI and ultrasound use no ionizing radiation. They are excellent substitutes for many indications, but not all — CT is faster and better for lungs, bones, and acute trauma. Your provider chooses the test based on what they need to see.
Can children safely get a CT scan?
Yes, when the test is clinically necessary. We use size-based pediatric protocols that deliver significantly less radiation than the adult-equivalent scan.
What is ALARA?
ALARA stands for "As Low As Reasonably Achievable." It is the radiology profession's commitment to use the smallest radiation dose that still produces a diagnostic-quality image.
Can I see my dose report?
Yes. CT dose information (CTDIvol and DLP) is recorded for every scan. Ask the technologist or contact us afterward — we will provide it on request.
I'm pregnant — should I avoid CT?
CT during pregnancy is generally avoided unless the information is essential and cannot be obtained another way. Always tell our team if you are or could be pregnant.