The majority of tests are conducted with an ultrasonic device outside the body, however it is sometimes necessary to use a device within your body. Sonographers employ diagnostic ultrasonography as a diagnostic technique. Therapeutic ultrasonography also employs sound waves that are above the human hearing range, but it does not generate pictures. These high-intensity sounds are used to treat patients by causing vibrations that move small particles inside the tissue. This process has many names including acoustic radiation force impulse (ARFI), mechanical vibration therapy, and microsonic therapy. Diagnostic ultrasonography uses the echoes from various tissues in order to create images of the body for diagnosis. These images are useful for detecting disease or abnormalities. The quality of the image depends on several factors such as the sonographer's experience, the machine being used, and the type of tissue being scanned. There are two main types of diagnostic ultrasonography: linear and radial. Linear ultrasonography produces a line of sight across the tissue being examined, while radial scans cover an area around the center point. Both methods can be used to scan internal organs such as the heart or blood vessels, but they each have their advantages and disadvantages. For example, because linear scanning covers more area than radial scanning, it is better at showing large areas of tissue containing multiple lesions while radial scans are more effective at pinpointing specific problems.