![]() ![]() Note that the arrangement can be horizontal as illustrated below, or vertical, depending on the tool configuration. There is a toolbar in the VOI interface which collects the different VOI editing modes. These VOIs are very helpful for cropping the image to a part of interest (for instance the brain in rat images), and also as restrictions to be applied in region-growing VOIs. Other object VOIs remain analytically defined and can easily be scaled and moved in all directions. After the creation they behave like normal contour VOIs. Some of the objects generate a stack of contours in a number of contiguous slices. Regular VOIs: There is a list of regular objects (cube, sphere, etc) which can be generated centered at a defined point in the image.The Auto-Iso-contour Mode requires a restricting VOI, within which the outlining is performed. The function can look for cold or hot objects, and can also generate multiple contours per slice to outline disconnected structures. ![]() Auto-Iso-contour Mode: This mode is similar to the Iso-contour ROI mode, but is generating iso-contours at a well-defined threshold in a whole volume.This way of defining VOIs is most flexible, and recommended when tight control is required, for example when working with small animal data. Single Pixel Mode: The user can click at individual image pixels to add or remove them from a contour VOI.This is an easy way to outline objects with a clear contrast to background in a single slice, but cannot be extended in an easy way to consistently outline the same object in multiple slices. Iso-contour ROI Mode: There is a pseudo-snake function which follows pixels with similar values to enclose the largest object in the slice.This will create a contour which is well-defined but relatively difficult to adjust because of the many vertices which have to be moved. Draw Mode: Drawing a trajectory with closely spaced vertices by holding down the left mouse button and dragging along an anatomical structure.It is easy to adjust, but tends to be coarse. This will create a contour with relatively sparse vertices. Edit Mode: Manually outlining a contour polygon by clicking with the left mouse button at vertex points.There are several methods for generating contours: ![]()
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