What is the primary difference between sealed and unsealed radiation?

The primary difference between sealed and unsealed radiation is that sealed radiation generally refers to solid radioactive sources that are encapsulated in a way that prevents the release of radioactive material, while unsealed radiation involves radioactive substances that are not contained and can exist in liquid or gas forms. In practice, sealed sources are often used in brachytherapy for cancer treatment, where the radioactive material is placed in or near the tumor, limiting exposure to surrounding tissues. Conversely, unsealed sources might be injected or ingested, which introduces radioactivity into the body in a form that can spread, affecting various tissues or organs.

Recognizing the distinction is crucial for understanding their applications and potential risks. Sealed radiation is utilized in ways that minimize systemic exposure and target therapy directly, while unsealed radiation allows for broader therapeutic options, including diagnostic imaging and treatment for certain medical conditions, though it may carry increased risk due to the potential for whole-body exposure.