Histogram

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Histogram.jpg
HistogramDialog.PNG

This function can be used to displays a histogram distribution of the whole image or a selected ROI, display intensity profiles, or show time profiles. It can be accessed by the button on the top toolbar shown to the right.

Algorithm

Histogram

Displays a histogram of a region of interest or the entire image. The histogram that is displayed is determined in the following order:

  1. If a boundary is present the histogram always represents the 2D ROI enclosed by that boundary
  2. If no boundary is present and the user has right clicked on an object then the histogram is the 3D ROI defined by that object
  3. If no boundary is present and the last right click was not on an object then the histogram is for the entire 2D image

To display a histogram of an object click click on the object then directly click on the histogram button on the top toolbar.

Intensity Profile

If a boundary is drawn on the image but is not closed (by double clicking) an intensity profile will always be displayed.

Time Profile

If the current image is a 4D series the histogram tool can be used to display a time series. To display a time series:

  1. Verify a 4D series is loaded (the next/previous time point buttons will be enabled)
  2. Mark a single point voxel of interest (click once), or a region of interest with a boundary
  3. Click on the histogram button on the top toolbar
  4. For the ROI click the check box "Time Profile"

For the single voxel the time profile of that single voxel is displayed. If an ROI is selected then the time profile of the mean for that region will be displayed.

Histogram Input

Number of bins - Sets bin size to achieve the entered number of bins.
Width of bin - Sets number of bins to achieve entered width of bin.
Grid off - Toggles a grid overlay on the histogram.
Bar - Toggles between a bar graphs display (default for histogram) and a line graph display (default for profiles).
Time profile - For 4D images only, displays a time profile for a voxel or region selected with a boundary.
Reflect in Image - Colors the selected intensity range red in the source image. The intensity range is selected by dragging the slider bars located below the histogram graph.
Export to Excel - Exports the intensity and number of voxels table to excel.
Scale Points - First scale point and second scale point set the lower and upper intensities used to generate a new histogram with the "Scale It" option.
Scale It - Generates a new histogram over a limited range specified by the first and second "Scale Points".
Clear - Clears the selected "Scale Points".

Histogram Output

Displays either a histogram graph and a table of all intensities and their frequency, or a profile graph and a table of location and intensity.

Note: The table of intensities on the right of the screen and the excel export are integer values. If the image consists of floating point values (decimal numbers) they will be rounded off. However, the mean and standard deviation will reflect the original float values.