Radiation that deflects off the patient's head while exposing digital images is referred to as:

The term "scatter radiation" refers to the radiation that has been deflected from its original path after interacting with matter, such as a patient’s body. In the context of medical imaging, when X-rays are produced during a procedure, some of these X-rays may not travel straight through the patient to the detector; instead, they may strike the patient's head and scatter in different directions. This scattered radiation can contribute to the exposure on digital images but does not provide useful information for the image itself.

Understanding scatter radiation is vital for ensuring patient safety and quality of imaging, as it helps in minimizing unnecessary exposure. In contrast, characteristic radiation and primary radiation refer to different processes and types of radiation, which do not accurately describe the phenomenon of radiation deflecting after interacting with a patient. Background radiation is a general term for the radiation present in the environment, also not applicable in this scenario.