Hi Dear, An MRI is a series of detailed picture of your brain, as they were at the time the MRI was done. They are valid as long as no other changes occur. Basically, if somebody has an MRI today that is normal, and have a stroke or hernia tomorrow, obviously the result will change (You never know).
Undo an action. Press Ctrl+Z or click (Undo) in the ribbon until you've fixed your mistake. You can't undo some actions, such as clicking commands on the File tab or saving a file. If you can't undo an action, the Undo command is dimmed.
Macintosh computers have a special command key marked by a four-leaf clover or an apple. The Command key is similar to a PC's Alt key-- you hold it down while pressing another key to execute some operation. Typically, command-key combinations are shorthands for menu choices. For example, on the desktop, pressing the Command key and O is equivalent to selecting the open option from the file menu. The Command key is sometimes called the Apple key or Open Apple.