Which of the following terms is unrelated to the others

A)  positron emission tomography 
B)  computerized tomography scan 
C)  electroencephalograph 
D)  reticular activating system

Positron Emission Tomography

A medical imaging technique that produces a three-dimensional image of functional processes in the body by detecting pairs of gamma rays emitted indirectly by a positron-emitting radiotracer.

Computerized Tomography

A diagnostic imaging technique that uses a series of X-ray images taken from different angles to create cross-sectional images of the bones, blood vessels, and soft tissues inside your body.

Reticular Activating System

A network of neurons located in the brainstem that plays a crucial role in controlling arousal and wakefulness.