Region of Interest (ROI)

Nexus event files contain Processing Variables (PV) as metadata. The following PV’s define two rectangular regions of interest (ROI) in the detector:

  • ROI1StartX, ROI1SizeX, ROI1StartY, and ROI1SizeY define the first ROI.

  • ROI2StartX, ROI2SizeX, ROI2StartY, and ROI2SizeY define the second ROI.

mr_reduction invokes Mantid algorithm MRInspectData to extract these ROI and then determine the peak range (peak width along the horizontal axis) and the low-resolution range (peak width along the vertical axis). If one of the ROI is bounded by the other, the bounded ROI is considered the peak and the bounding ROI is considered the background.

The following diagram illustrates the logic implemented in MRInspectData when determining the peak and background regions:

ROI extraction from the sample logs

(user/media/roi_pv_digest.puml)