<qa>  What is the name of the study that conducted to more fully evaluate how carbidopaThis study conducted to more fully evaluate the way that carbidopalevodopa and entacapone may work in the brain. This research study uses 123I-IBZM and dynamic SPECT imaging to determine the amount and the duration of dopamine release from specific regions in the brain after treatment with either the combination of carbidopalevodopa or the combination of carbidopalevodopaentacapone. 