Region of Interest
The English term Region of Interest ( ROI ) means “area of interest”. It is generally used to select a range from a measurement curve and to evaluate it statistically (e.g. maximum value, mean value, width of a peak , area under the curve). Counting rates that were recorded over time, spectrally or along a path are often used as measurement curves.
It is also used as a two- or three-dimensional area in computer-aided image processing and imaging processes and is often found in nuclear medicine .
Choices for ROIs
ROIs can be created manually, semi-automatically or fully automatically by evaluation software. One differentiates:
- Manual ROI: The user draws an area himself or herself using a keyboard, computer mouse , light pen or joystick .
- Semi-automatic ROI: The evaluation software supports the user in drawing the ROI. For example, the user only draws one line, the evaluation software automatically closes it and thus defines the evaluation area. Or: The user roughly defines an area within which the evaluation software determines a region that is defined by points that have values above a threshold specified by the user.
- Fully automatic ROIs: The evaluation software determines the demarcation criteria without operator intervention.
Multi-dimensional ROIs
Usually, the image area of interest is an examined organ or a representative underground region. One can compare an ROI with a measuring probe in the image area of any size and shape. The parameters examined within an ROI can be, for example: count rate (number per unit of time), SUV ( Standardized Uptake Value ) in positron emission tomography , course of the count rate over a time course in scintigraphy of the kidney or Hounsfield value in computed tomography .
ROIs can not only be created in the two-dimensional image area, but also describe three-dimensional structures in space.
source
- Udalrich Büll, Gustav Hör (ed.): Clinical nuclear medicine. 2nd Edition. VCH Verlagsgesellschaft, 1990, ISBN 3-527-15427-2 .