The Normalize checkbox normalizes isodose displays to the displayed value (e.g. 1.0 by default) at the point selected in the popup menu. The default normalization point is the prescription (Rx) point.
When the plaque is empty, the dose at the prescription (Rx) point is zero, so the normalization menu substitutes Rx Dose (e.g. 85 Gy) for Rx Point.
The normalization point can be changed to various locations (e.g. the tumor apex) from the Normalize at pop-up menu.
Plaque 1..4 - Selects the plaque (and its associated dose matrices) that is currently "active". Each plaque has its own legend settings.
The Legends pull-down menu lists the legend (.idos6) files that are in Plaque Simulator's master data folder and the most recently selected file. Note: if the legend settings have changed significantly since a legend file was opened, the Legends control will display Select rather than the file name.