Region of interest

A region of interest (often abbreviated ROI) is a sample within a data set identified for a particular purpose. The concept of a ROI is commonly used in many application areas. For example, in medical imaging, the boundaries of a tumor may be defined on an image or in a volume, for the purpose of measuring its size. The endocardial border may be defined on an image, perhaps during different phases of the cardiac cycle, for example, end-systole and end-diastole, for the purpose of assessing cardiac function. In geographical information systems (GIS), a ROI can be taken literally as a polygonal selection from a 2D map. In computer vision and optical character recognition, the ROI defines the borders of an object under consideration. In many applications, symbolic (textual) labels are added to a ROI, to describe its content in a compact manner. Within a ROI may lie individual points of interest (POIs). 1D dataset: a time or frequency interval on a waveform 2D dataset: the boundaries of an object on an image 3D dataset: the contours or surfaces outlining an object (sometimes known as the Volume of Interest (VOI)) in a volume 4D dataset: the outline of an object at or during a particular time interval in a time-volume A ROI is a form of Annotation, often associated with categorical or quantitative information (e.g., measurements like volume or mean intensity), expressed as text or in a structured form. There are three fundamentally different means of encoding a ROI: As an integral part of the sample data set, with a unique or masking value that may or may not be outside the normal range of normally occurring values and which tags individual data cells As separate, purely graphic information, such as with vector or bitmap (rasterized) drawing elements, perhaps with some accompanying plain (unstructured) text in the format of the data itself As a separate structured semantic information (such as coded value types) with a set of spatial and/or temporal coordinates Medical imaging standards such as DICOM provide general and application-specific mechanisms to support various use-cases.