A dental CT scan, often referred to as Cone Beam Computed Tomography (CBCT), involves exposure to ionizing radiation, but the amount is relatively low compared to many other medical imaging procedures. Typically, a dental CT scan delivers a radiation dose ranging from about 20 to 200 microsieverts (µSv), depending on the machine, scan settings, and area scanned. To put this in perspective, this dose is higher than a single traditional dental X-ray, which usually emits around 5 µSv, but significantly lower than a conventional medical CT scan of the chest or abdomen, which can range from several millisieverts (mSv) up to 16 mSv or more.
Radiation dose in dental imaging is measured in microsieverts (µSv) or millisieverts (mSv), where 1 mSv equals 1,000 µSv. The average person is naturally exposed to about 3 mSv (3,000 µSv) of background radiation annually from environmental sources like cosmic rays and radon gas. A typical dental CBCT scan’s radiation dose, therefore, is a small fraction of this yearly background exposure.
Dental CBCT scans use a cone-shaped X-ray beam to capture detailed 3D images of the teeth, jaw, and surrounding structures. This technology provides much more comprehensive information than standard 2D dental X-rays, which is crucial for complex diagnoses and treatment planning such as implant placement, orthodontics, and evaluation of jaw disorders. Despite the increased radiation compared to traditional dental X-rays, CBCT scans are designed to minimize exposure by focusing only on the area of interest and using lower doses than full medical CT scans.
The radiation dose from a dental CBCT scan varies widely depending on the device and protocol. For example, some machines emit doses as low as 20 µSv, while others may go up to 200 µSv or slightly more. This range is influenced by factors such as:
– **Field of View (FOV):** Smaller FOVs that scan only a few teeth or a limited jaw segment reduce radiation dose compared to larger FOVs covering the entire jaw or skull.
– **Resolution settings:** Higher resolution scans require more radiation to produce finer detail.
– **Scan time and machine technology:** Newer machines often use advanced detectors and software to reduce dose while maintaining image quality.
For comparison, a single traditional dental X-ray typically exposes a patient to about 5 µSv, and a full-mouth series of dental X-rays might total around 150 µSv. A panoramic dental X-ray, which captures the entire mouth in one image, usually delivers between 10 and 30 µSv. Thus, a dental CBCT scan generally exposes a patient to radiation somewhere between a panoramic X-ray and a full-mouth series, but with the added benefit of 3D imaging.
While the radiation dose from dental CT scans is low, it is still important to use these scans judiciously. The principle of ALARA (As Low As Reasonably Achievable) guides dentists and radiologists to minimize radiation exposure by only ordering scans when necessary for diagnosis or treatment planning. Protective measures such as lead aprons and thyroid collars are often used during dental imaging to shield sensitive tissues from scatter radiation.
Children are more sensitive to radiation than adults, so dental professionals take extra care to limit their exposure. Digital imaging technology has also helped reduce doses significantly compared to older film-based systems.
In terms of risk, the radiation dose from a dental CT scan is considered very low and unlikely to cause harm when used appropriately. The risk of radiation-induced cancer from a single dental CBCT scan is extremely small, especially when weighed against the diagnostic benefits that can prevent more serious health issues. However, repeated scans should be avoided unless clinically justified.
In summary, a dental CT scan contains a small amount of radiation, typically between 20 and 20
