圆形 ROI 工具。它可以水平和垂直缩放，从而形成一个椭圆。如果 ROI 的长宽比不等于 1:1，还可以进行旋转。
要以恒定的纵横比缩放圆形，请按下 "Shift "键。
图用于定义 "感兴趣区"（ROI）的圆形
减法圆或椭圆 ROI 绘制工具
减法圆或椭圆 ROI 绘图工具的操作方法与加法工具相同，但区域定义为 "非感兴趣区"。
有关处理减法绘图工具的信息，另请参阅 ROI 工具的应用顺序。
A circular ROI tool. It can be horizontally and vertically scaled and thus formed into an ellipse. If the ROI has an aspect ratio not equal to 1:1, it can also be rotated.
To scale the circle with constant aspect ratio, press the "Shift" key.
Fig.: Circular shape for defining a "region of interest" (ROI)
Subtractive circle or ellipse ROI drawing tool
The subtractive circle or ellipse ROI drawing tool can be manipulated in the same way as the additive one, but the area is defined as "not of interest".
For information about handling subtractive drawing tools, see also Order of application for ROI tools.