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Table 1 Types of measurements made

From: High-throughput mammographic-density measurement: a tool for risk prediction of breast cancer

Area measurements
Count Numbers of particles
TotalArea Area of selection in square pixels
AverageSize Average size of each particle (TotalArea divided by count)
Area Fraction The percentage of pixels in the image or selection that have been thresholded
Intensity measurements
Mean gray value Average gray value within the selection. This is the sum of the gray values of all the pixels in the selection divided by the number of pixels
Modal gray value Most frequently occurring gray value within the selection. Corresponds to the highest peak in the histogram
Median The median value of the pixels in the image or selection
Shape descriptors
Circularity 4π (area/perimeter2). A value of 1.0 indicates a perfect circle. As the value approaches 0.0, it indicates an increasingly elongated polygon. Values may not be valid for very small particles
Solidity Area/convex area
Others
Integrated density The sum of the values of the pixels in the image or selection. This is equivalent to the product of Area and Mean Gray Value
Skewness The third-order moment about the mean
Kurtosis The fourth-order moment about the mean
Perimeter The length of the outside boundary of the selection
Fit ellipse Fit an ellipse to the selection. Uses the headings Major, Minor, and Angle. Major and Minor are the primary and secondary axis of the best-fitting ellipse. Angle is the angle between the primary axis and a line parallel to the × axis of the image
  1. The Analyze command in ImageJ counts and measures objects in thresholded images. It works by scanning the selection until it finds the edge of an object. It then outlines the object by using the wand tool, measures it by using the Measure command, fills it to make it invisible, and then resumes scanning until it reaches the end of the image or selection.