A neck CT scan typically exposes a patient to about **2 to 4 millisieverts (mSv)** of radiation, though this can vary depending on the specific scanner settings and protocols used. This dose is considered moderate compared to other CT scans but significantly higher than standard X-rays.
To understand what this means, it helps to know that radiation dose in medical imaging is measured in millisieverts, which accounts for the type of radiation and sensitivity of different tissues. For context, an average person receives about 3 mSv per year from natural background radiation. So a neck CT scan roughly equals one year’s worth of natural exposure or slightly more.
The amount of radiation depends on several factors:
– **Scanner technology:** Newer machines often use lower doses due to improved detectors and software.
– **Scan parameters:** Higher X-ray tube current or voltage increases dose; spiral scanning with low pitch or retrospective gating can also raise exposure.
– **Patient size:** Larger patients may require higher doses for clear images.
– **Purpose of scan:** Sometimes contrast-enhanced scans or multiphase studies increase total exposure.
Radiation from a neck CT primarily affects tissues in the scanned area—skin, muscles, thyroid gland, lymph nodes—and some scattered dose reaches nearby organs like the brain and upper chest structures. The thyroid is particularly sensitive to ionizing radiation because it contains rapidly dividing cells prone to DNA damage.
At the cellular level, ionizing radiation damages DNA either directly by breaking strands or indirectly by creating reactive molecules that harm cell components. Most cells repair this damage successfully; however, errors during repair can cause mutations that might lead to cancer over time. This risk increases with cumulative exposure but remains low for single diagnostic scans.
Health experts distinguish between two types of effects:
1. **Tissue reactions** occur only above certain high-dose thresholds (much higher than those from diagnostic CTs) causing burns or organ dysfunction.
2. **Stochastic effects** like cancer have no known safe threshold; even small doses carry some risk proportional to dose but very low at typical medical levels.
Because repeated imaging adds up cumulatively over years if done frequently without clear indication, doctors follow principles such as ALARA (“As Low As Reasonably Achievable”)—using minimal necessary doses and alternative methods when possible—to reduce unnecessary risks while benefiting diagnosis.
In practical terms:
– A single neck CT’s effective dose around 2–4 mSv translates into a very small increase in lifetime cancer risk—on the order of a few cases per 100,000 people scanned.
– For comparison: chest X-rays deliver about 0.02 mSv each (much less), while abdominal CTs may reach 8–10 mSv (higher).
– MRI and ultrasound do not use ionizing radiation at all but are not always suitable substitutes depending on clinical needs.
Patients should discuss with their healthcare providers why a neck CT is recommended versus other imaging options and ensure scans are justified based on symptoms or findings rather than routine screening without cause.
Overall, while any ionizing radiation carries some risk due to potential DNA damage leading possibly to cancer decades later, modern neck CT protocols balance image quality against minimizing exposure so that benefits outweigh these small risks for most patients needing detailed evaluation of throat structures such as airway problems, tumors, infections or vascular abnormalities.
