Additional Study Information: The purpose of this study is to test the effects of an investigational drug called crenezumab for the treatment of Alzheimers disease. This study will use MRI scans to look at the effects of this treatment on the brain. This study will be conducted in many centers around the world, and it is important that the MRI scans are always performed in a similar fashion throughout the study. We hope that the use of MRI scanning will provide us with a better understanding of how the drug is working in changing the course of Alzheimers disease. There are rigorous quality control processes in place to ensure that the measurements are consistent both across imaging centers and for the duration of the study. An important part of the quality control process involves comparing images from MRI brain scans to ensure that the parameters used by the scanner have not changed. You are being asked to assist with these quality control processes by volunteering to have an MRI brain scan for the purposes of determining scanner image quality for Study BN29552.