Define SRS grid layout
Physical Fractionator - step 6
The Systematic Random Sampling (SRS) grid size defines how close your counting frames are to each other.
- With a smaller grid, you will visit more sites within the traced contour, and count more cells as a result.
- With a larger grid, you will visit fewer sites, allowing for more efficient counting, but potentially increasing your Coefficient of Error and leading to a less precise estimate.
We recommend a parameter determination study to determine an appropriate grid size. Also see Determining Sampling Precision.
Manually enter the grid size
- Type in "X" and "Y" spacing.
- Click Display Changes.
OR
Use a percentage of the ROI.
OR
Determine grid size based on number of sampling [sites]
If you don’t know the "X" and "Y" spacing, the program can calculate spacing based on the region in a representative section.
For instance, if you want a spacing to obtain a mean of 10 sites based on this representative section, set the grid size to include approximately 10 counting frames in the region of interest:
- Enter the desired number of sites to the right of Approximate Sites.
- Click Estimate Grid Size.
Grid size and counting frame size remain consistent throughout all of the sections for a given region of interest. The number of sites, however, changes every time because the grid is applied randomly every time you start a new probe run. Click Display Changes repeatedly to see how the grid is applied differently every time creating a slightly different number of sites.
Advanced Features
Enables you to rotate the grid.
Grid rotation is only necessary when working on a tall, slim region of interest (e.g., spinal cord).
Grid rotation can be used to increase efficiency. For instance if you have a longitudinal section of spinal cord that is not vertically placed on the slide, you could rotate the grid to match the section orientation. This would make it more likely for your square or rectangular disectors to fall on the tissue, thus increasing efficiency but remaining unbiased.