Dr. yen is a clinical psychologist studying the onset of psychological disorders, such as schizophrenia. dr. yen will most likely use a(n) to get a glimpse of his subjects brains.

Dr. Yen will most likely use a Magnetic Resonance Imaging or MRI to diagnose mental illness.  This machine uses radio waves to take a series of shots of the person to capture details about the tissue inside the body. These waves will then form an image. The machine will produced a 3D image that will be shown on a screen.

MRI scans help experts to assist with symptoms that are more mental than physical.  If a person has a sudden change of behavior which can be attributed as symptoms of a mental illness, an MRI scan will be requested to find out what causes it and to make sure that the cause is not a physical damage in the brain.

The answer is metaphase