0

I constructed an experiment with Gaussian blur in real world and MR images. I printed some test images blurred and compare augmented images blurred too.

What is the best way to express how much blurring I applied in real-world coordinates?

The image is 2560x1440 pixels, corresponding to 533x300 cm in the real world. If this image is blurred with a Gaussian with standard deviation n (filter size is ceil(3 * n) * 2 + 1), how can this be expressed in centimeters? Is it reasonable to express it as the real size of the filter in centimeters?

Cris Luengo
  • 55,762
  • 10
  • 62
  • 120
Buster Chung
  • 11
  • I edited your text to clarify it. I hope that I didn't mis-represent your question. Please review. There is an 'edit' link at the bottom of your question, right underneath the tags, that you can use to further fix up the question, or correct my edits if they are wrong. – Cris Luengo Mar 26 '18 at 14:56
  • Are you sure it is 533x300 cm and not millimeters? 533 cm is 5.3 meters. That is way larger than any MR machine I've seen! – Cris Luengo Mar 26 '18 at 14:59

1 Answers1

0

In short, yes, it is perfectly reasonable to express the size of the kernel in real-world coordinates.

In your case, you have 533 cm == 2560 pixels horizontally, which is 0.2082 cm per pixel. (Please edit if the question has a mistake and this should be mm instead of cm.) Vertically you have approximately the same, so we can assume isotropic sampling and leave it at 0.208 cm/px.

Given that pixel size, a standard deviation of the Gaussian of n is equivalent to a standard deviation of 0.208*n cm in the real world.

Cris Luengo
  • 55,762
  • 10
  • 62
  • 120