# Area and perimeter

Good afternoon people! I need help with ImageJ.

I would like to measure the area and perimeter of intestinal microvilli (structures that are in the images). I measured microvilli in two ways and got different results.

In the first, I used straight and adjusted by the line width command to cover the microvilli shape (image 1). In the second, I used freehand selections to get around microvilli (image 2).

Looking at the results (image 3), I obtained a small difference for the area, but for the perimeter using freehand selections, the value was much higher.

Could someone tell me what is the most correct way to measure these two parameters?

I thank the attention!

The second approach is the correct measurement for getting the perimeter directly.

For the line tool you can take the length and the width and and compute the perimeter.
Less work than the second approach. But more of an approximation.

If at the end you are only interested in averages you could just measure the lenght and width of a couple of microvilli and count them. Seems less work but maybe depends on the required granularity of your measurement.

Thanks a lot for the help! This is going to be my first experience with ImageJ.

I will also measure the length and width, but I would use the line tool.

I think also that the second way of measuring will be a lot of work, but I will make a comparison between calculating the perimeter and measuring to see the difference.

I think that to calculate the perimeter I will have to use the ellipse formula, as it is the format most similar to the microvilli.

What do you think?

or a rectangle? Iâ€™m in doubt about it

From what I see your structures can be best described as rectangles with one end having rounded corners and the other end a half circular/oval structure.

If one thinks about it, the variables length and width will have the biggest effect on the area and perimeter. Whereas measuring the end structures more accurately might contribute very little to reduce errors in the measurement. So just measuring length and width alone might be sufficient to describe your structures in a quantitative manner. Except you are specifically interested in the end structures.

It depends all on your question, what you want to compare and how granular your measurement should be.

I personally would start out with quick and easy measurements, that are approximations. One can always extend later if those are insufficient.

I agree with you. I made the comparison between measuring manually and calculating using length and width, and the difference between the values â€‹â€‹was very small. I believe that for what I need to know in my work there will be no problem being calculated.

One of the stages of my work is to observe if there is an influence on the morphology (length, width, and perimeter), disposition and integrity of the microvilli of fish in the different treatments.

Thank you so much for your help, it was very important! See you

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