The purpose of this research study is to measure how many of the dopamine receptors lurasidone occupies throughout the brain of patients with schizophrenia or schizoaffective disorder and over what time period the occupancy occurs. This is research because lurasidone is an investigational medication that has not yet been approved by the Food and Drug Administration (FDA). Dopamine receptors have key roles in many processes, including the control of motivation, learning, and fine motor movement. The degree of occupancy and the transience of occupancy D2 receptor occupancy for optimal clinical response and to prevent relapses is a controversial area that this study will address.